While exciting, observing marine life in their environment comes with a risk. Injuries, though rare, may occur as a result of an uninformed swimmer or diver’s actions. The Hazardous Marine Life reference book examines the most common hazardous marine life that water enthusiasts may encounter and introduces the mechanisms of injury, techniques for injury prevention and application of first aid.

In this book, you’ll learn about:

• Chapter 1 – Envenomations
  • Fire Coral
  • Portuguese Man-of-War
  • Poisson-lion
  • Blue-Ringed Octopus
  • Box Jellyfish
  • Cone Snails
• Chapter 2 – Traumatic Injuries and Complications
  • Skin Abrasions
  • Stingrays
  • Sea Urchins
• Chapter 3 – Seafood Poisonings
  • Ciguatera
  • Empoisonnement des poissons par les scombridés
  • Marée rouge et intoxications par les coquillages
• Chapter 4 – Appendix
  • Thermolyse
  • Antivenins
  • Technique d'immobilisation par pression

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Crédits :

Rédacteur en chef : Petar Denoble, MD, DSc
Editor: Matias Nochetto, MD

“Toxicity is in the dose.”

Envenomation is a process by which a venom or toxin is injected into another being via a bite, puncture or sting. Envenomation is always due to direct contact with an animal (or parts of it like drifting jellyfish tentacles). There are two possible mechanisms of injection: active, such as jellyfish or cone snails, or passive like lionfish or sea urchins. Injuries typically occur during shore entries or exits, incidental contact or deliberate attempts to handle a specimen. Envenomations are rare but can be life-threatening and may require rapid first aid response. In this chapter, we will cover some common envenomations as well as some of the more rare, but serious cases.

Dans ce chapitre, vous apprendrez ce qui suit :

• Fire Coral
• Portuguese Man-of-War
• Poisson-lion
• Blue-Ringed Octopus
• Box Jellyfish
• Cone Snails

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Fire Coral

Fire corals are colonial marine cnidarians that when touched can cause burning skin reactions. Fire coral-related incidents are common among divers with poor buoyancy control.

Biology and Identification

Fire coral, which belong to the genus Millepora, are found in tropical and subtropical waters around the world. Generally fire coral adopts a yellow-green or brownish branchy formation, although its external appearance often varies due to environmental factors. Because fire coral can colonize hard structures, it can even adopt a rather stony appearance with rusty coloration.

Despite their calcareous structure, fire coral is not a true coral; these animals are more closely related to Portuguese man-of-war and other hydrozoans.

Mechanism of Injury

Fire coral gets its name because of the fiery sensation experienced after coming into contact with a member of the species. The mild to moderate burning that it causes is the result of cnydocites embedded in its calcareous skeleton; these cnydocites contain nematocysts that will fire when touched, injecting their venom.

Signes et symptômes

The burning sensation may last several hours and is often associated with a skin rash that appears minutes to hours after contact. This skin rash can take several days to resolve. Often, the skin reaction will subside in a day or two, but it may likely reappear several days or weeks after the initial rash disappeared.

Fire coral lacerations, in which an open wound receives internal envenomation, are the most problematic fire coral injuries. Venom from Millepora spp. is known to cause tissue necrosis on the edges of a wound. These injuries should be carefully observed, as necrotic tissue provides a perfect environment to culture serious soft tissue infections.

Prévention

• Avoid touching these calcareous formations.
• If you need to kneel on the bottom, look for clear sandy areas.
• Remember that hard surfaces such as rocks and old conchs may be colonized by fire coral even if they do not look branchy.
• Always wear full-body wetsuits to provide protection against the effects of contact.
• Master buoyancy control.
• Always look down while descending.

Premiers soins

1. Rinse the affected area with household vinegar.
2. Redness and vesicles will likely develop. Do not puncture them; just let them dry out naturally.
3. Keep the area clean, dry and aerated—time will do the rest.
4. For open wounds, seek a medical evaluation.
   NOTE: Fire coral venom is known to have dermonecrotic effects. Share this information with your physician before any attempts to suture the wound, as the wound edges might become necrotic.
5. Antibiotics and a tetanus booster may be necessary

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Portuguese Man-of-War

Portuguese man-of-wars are free-floating cnidarians characterized by blue gas-filled bladders and long tentacles that drift on the surface of the ocean. Contact with a man-of-war’s tentacles can cause intense pain and other systemic symptoms.

Biology and Identification

There are two species for the genus: Physalia physalis in the Atlantic and Physalia utriculus in the Indo-Pacific. The Atlantic man-of-war may reach slightly larger dimensions, with the gas bladder rarely exceeding one foot (30 centimeters) and tentacles averaging 33 feet (10 meters) and possibly extending up to 165 feet (50 meters).

Though many people mistake the Portuguese man-of-war for species of jellyfish, this genus belongs to the order Siphonophora, a class of hydrozoans. What we see as a single specimen is actually a colony composed of up to four different types of polyps. Despite its resemblance, these animals are more closely related to fire coral than to jellyfish.

The Portuguese man-of-war is easily recognizable; if you see blue tentacles, you can bet they belong to Physalia.

Risk to Humans

The man-of-war’s polyps contain cnidocytes delivering a potent proteic neurotoxin capable of paralyzing small fish. For humans, most stings cause red welts accompanied by swelling and moderate to severe pain. These local symptoms last for two to three days.

Systemic symptoms are less frequent, but potentially severe. They may include generalized malaise, vomiting, fever, elevated heart rate at rest (tachycardia), shortness of breath and muscular cramps in the abdomen and back. Severe allergic reactions to the man-of-war’s venom may interfere with cardiac and respiratory function, so divers should always seek a timely professional medical evaluation.

Épidémiologie

Approximately 10,000 cnidaria envenomations occur each summer off the coasts of Australia, the vast majority
of which involve Physalia. In fact, man-of-wars cause the most cnidarian envenomations prompting emergency evaluation globally. The risk may not be so great for divers, however, as most Physalia stings occur on beaches or on the surface of the water rather than while submerged. Certain regions are known to have seasonal outbreaks, but incidence is highly variable between regions.

Prévention

• Always look up and around while surfacing. Pay special attention during the last 15-20 feet of your ascent, since this is the area where you may find cnidarians and their submerged tentacles.
• Wear full body wetsuits regardless of water temperature. Mechanical protection is the best way to prevent stings and rashes.
• In areas where these animals are known to be endemic, a hooded vest may be the best way to protect your neck.

Premiers soins

1. Avoid rubbing the area. Cnidarian tentacles are like nematocyst-coated spaghetti, so rubbing the area or allowing the tentacles to roll over the skin will exponentially increase the affected surface area and, therefore, the envenomation process.
   NOTE: Initial pain may be intense. Though life-threatening complications are rare, monitor circulation, airway and breathing, and be prepared to perform CPR if necessary.
2. Remove the tentacles. You must take great care to remove the man-of-war’s tentacles in order to avoid further envenomation. Those distinctive blue tentacles are quite resistant to traction, so you can remove them fairly easily with some tweezers or gloves.
   NOTE: If you do not have access to tweezers or gloves, the skin on your fingers is likely thick enough to protect you. Keep in mind, however, that after removal your fingers may contain hundreds or even thousands of unfired nematocysts, so pretend you have been handling hot chili peppers that cause blisters anywhere you touch and treat your fingers as recommended from the next step on.
3. Flush the area with seawater. Once the tentacles and any remnants have been removed, use a high volume syringe and flush the area with a powerful stream of seawater to remove any remaining unfired nematocysts. Never use freshwater since this will cause unfired nematocysts to fire.
4. Apply heat. Immerse the affected area in hot water (upper limit of 113°F/45°C) for 30 to 90 minutes. If you are assisting a sting victim, try the water on yourself first to assess tolerable heat levels. Do not rely on the victim’s assessment, as intense pain may impair his ability to evaluate tolerable heat levels. If you cannot measure water temperature, a good rule of thumb is to use the hottest water you can tolerate without scalding. Note that different body areas have different tolerance to heat, so test the water on the same area where the diver was injured. Repeat if necessary. If hot water is not available, apply a cold pack or ice in a dry plastic bag.
   NOTE: Application of heat has two purposes: 1) it may mask the perception of pain; and 2) it may assist in thermolysis. Since we know the venom is a protein that has been superficially inoculated, application of heat may help by denaturing the toxin.
5. Always seek an emergency medical evaluation.
6. Continue monitoring the patient until a higher level of care has been reached.

Vinegar Application

Use of vinegar is controversial with Physalia spp. Though the use of vinegar has traditionally been recommended, several studies both in-vivo and in-vitro show massive nematocyst discharge upon pouring household vinegar over certain species of cnidarians, including Physalia. Still, the most current American Heart Association guidelines (AHA 2010) recommend application of vinegar for all jellyfish, including Physalia spp. If anything changes, DAN will let you know.

If you do choose to apply vinegar, you can optimize application and significantly economize by using spray bottles. Generously spray the area with vinegar for no less than 30 seconds to neutralize any invisible remnants. Pick off any remaining tentacles.

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Poisson-lion

The lionfish is a genus of venomous fish commonly found in tropical reefs. Native to the Indo-Pacific, the fish is one of the most infamous invasive species in the western Atlantic. This voracious predator is not a threat to divers, but its introduction into exotic ecosystems can decimate juvenile specimens. In an attempt to control the spread of lionfish populations, recreational divers in the Americas have started aggressive campaigns to hunt them; in the process, many divers are stung with the lionfish’s sharp spines, which can cause very painful and sometimes complicated wounds.

Identification and Distribution

Lionfish, turkeyfish and zebrafish are common names for fish species of the genus Pterois, a subset of fish of the venomous Scorpaeniform family. Though lionfish are native to the Indo-Pacific, members of the order Scorpaenidae can be found in oceans all over the globe, even in arctic waters. Lionfish specimens are typically red with white and black stripes and have showy, spiky fins. Species include Pterois volitans, P. miles, P. radiata, and P. antenata among a few others.

Western Atlantic Invasion

Since the early 1990s, invasive lionfish have wreaked havoc on local juvenile reef fish populations in the western Atlantic. Out of the nine species of Pterois, only P. volitans and P. miles are found in Western Atlantic waters, but they range from as far north as Rhode Island down to Venezuela and The Guianas.

Risk to Humans

Knowing no predators, these fish are generally docile, allowing divers to approach closely enough and making themselves easy targets for spearfishing. Unfortunately, the desperate attempts to eradicate these fish from the Americas have caused a significant rise in the incidence of lionfish puncture wounds.

Épidémiologie

The prevalence and incidence of lionfish envenomations is unknown. Treating physicians may not choose to consult a poison control center, and in the United States are under no obligation to report these injuries to state or federal agencies. Scientific literature accounts for 108 cases of lionfish envenomations reported between 1976 and 2001, and almost all of these reports are actually from marine aquarists. It is impossible to know how often victims go untreated and how often treatment goes unreported, but the frequency of case reports seems to indicate that lionfish envenomations are not uncommon.

Lionfish culling tournaments are becoming more and more popular all over the Caribbean. Recent studies conducted by DAN staff from Cozumel, Mexico accounted over four years of tournaments. Incidence of injury during these events was between 7-10% of participants.

Mechanism of Injury

Most lionfish-related incidents occur as a result of careless handling, usually during spearfishing or while preparing them for consumption. Lionfish have needlelike spines located along the dorsal, pelvic and anal fins, and punctures can be extremely painful and lead to rapid development of localized edema and subcutaneous bleeding. Pain can last for several hours, edema typically resolves in two to three days, and tissue discoloration can last up to four or five days. Due to edema and the venom’s inherent toxicity, puncture wounds on fingers can lead to ischemia (restriction of blood supply to the tissues) and necrosis.

Prévention

Lionfish are by no means aggressive. To prevent injuries, maintain a prudent distance. If you are committed to engage in spearfishing or culling activities, avoid improvisations and do not try to handle these animals until you learn from more experienced divers.

Premiers soins

If you are stung, remain calm. Notify the dive leader and your buddy. The priority is to safely end your dive, returning to the surface following a normal ascent rate. Do not skip any decompression obligation.

On the surface, first aid providers should:

1. Rinse the wound with clean freshwater.
2. Retirer tout matériau étranger apparent.
3. Control bleeding if needed. It is ok to allow small punctures to bleed for a minute immediately after being stung (this may decrease venom load).
4. Apply heat. Immerse the affected area in hot water (upper limit of 113°F/45°C) for 30 to 90 minutes. If you are assisting a sting victim, try the water on yourself first to assess tolerable heat levels. Do not rely on the victim’s assessment, as intense pain may impair his ability to evaluate tolerable heat levels. If you cannot measure water temperature, a good rule of thumb is to use the hottest water you can tolerate without scalding. Note that different body areas have different tolerance to heat, so test the water on the same area where the diver was injured. Repeat if necessary.
   NOTE: Thermolysis can also be a secondary benefit worth pursuing, but it tends to be less effective in cases where the venom has been injected deep into the tissues.
5. Apply bandaging as needed.
6. Seek a professional medical evaluation.

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Blue-Ringed Octopus

Blue-ringed octopus are a small species of venomous octopi that live in tropical tide pools from south Japan to the coastal reefs of Australia and the western Indo-Pacific. These small octopi are the only cephalopods known to be dangerous to humans.

Identification

The blue-ringed octopus hardly ever exceeds eight inches (20 centimeters) in size. Their most distinctive feature is the blue iridescent rings that cover their yellow-colored body; however, it is important to emphasize that this feature is only displayed when the animal is disturbed, hunting or mating. When calm or at rest, the animal may display an overall yellowish, grey or beige coloration without any visible blue rings. The blue-ringed octopus is more active at night, spending most of the day hidden in its nest in shallow areas or tide pools.

Épidémiologie

Blue-ringed octopus envenomations are very rare. These animals are only endemic to southern Japan, Australia and the western Indo-Pacific. Cases outside of this region are generally due to deliberate handling of aquarium specimens. There are only a handful of reported fatal cases. Full recovery is expected with timely professional medical intervention.

Mechanism of Injury

As with all cephalopods, octopi have a strong beak similar to those of parrots and parakeets. All octopi have some sort of venom to paralyze their victims, but the blue-ringed octopus bite may contain an extremely powerful neurotoxin called tetrodotoxin (TTX), which can be up to 10,000 times more potent than cyanide and can paralyze a victim in minutes. Theoretically, a little over one-half milligram of this venom—the amount that can be placed on the head of a pin—is enough to kill an adult human. Certain bacteria present in the blue-ringed octopus’ salivary glands synthesize the toxin. TTX is not unique to the blue-ringed octopus; certain newts, dart frogs, cone snails and pufferfish can also be a source of TTX intoxication, though from different mechanisms.

Signes et symptômes

A blue-ringed octopus bite is usually painless or no more painful than a bee sting; however, even painless bites should be taken seriously. Neurological symptoms dominate every stage of envenomation, and manifest as paresthesia (tingling and numbness) progressing to paralysis that could potentially culminate in death. If envenomation has occurred, signs and symptoms usually start within minutes and may include paresthesia of the lips and tongue. This is usually followed by excessive salivation, trouble with pronunciation (dysarthria), difficulty swallowing (dysphagia), sweating, dizziness and headache. Serious cases may progress to muscular weakness, incoordination, tremors and paralysis. Paralysis may eventually affect respiratory muscles, which can lead to severe hypoxia with cyanosis (blue or purple tissue discoloration due to insufficient oxygen in the blood).

Prévention

These animals are not aggressive, and divers should not fear blue-ringed octopi. If encountered, avoid handling these animals. Due to their small size and lack of skeleton, a blue-ringed octopus den might be a small space only accessible through a tiny crevice, so avoid picking up bottles, cans or mollusk shells in areas they inhabit.

Premiers soins

Care is supportive. There is no antivenom available. If someone is bitten:

1. Clean the wound with freshwater and provide care for a small puncture wound.
2. Apply the pressure immobilization technique.
   NOTE: TTX is a heat-stable toxin, so the application of heat will not denature the toxin.
3. Watch for signs and symptoms of progressive paralysis.
   • Be prepared to provide mechanical ventilations with a bag valve mask device or a manually triggered ventilator.
   • Do not wait for signs and symptoms of paralysis. Always seek an evaluation at the nearest emergency department.
     NOTE: The bite site might be painless and still be lethally toxic.
4. Wound excision is never recommended.

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Box Jellyfish

Box jellyfish (cubozoans) are cube-shaped medusa notorious for possessing one of the most potent venoms known to mankind. Certain species can kill an adult human in as little as three minutes, scarcely enough time for any rescue response.

Biology and Identification

Medusas are the migrant form of cnidarians. In the case of box jellyfish, their bell-like body is cube shaped, with tentacles extending from each corner. Box jellyfish are complex animals with a propulsion mechanism and a relatively sophisticated nervous system for a jellyfish. They have up to 24 eyes, some of them with corneas and retinas, enabling them to not only detect light but also to see and circumnavigate objects to avoid collision.

While some jellyfish live off of symbiotic algae, box jellyfish prey on small fish, which are immediately paralyzed upon contact with their tentacles. Then the tentacles are retracted, carrying the prey into the bell for digestion. Some species hunt daily, and at night some species can be observed resting on the ocean floor.

Epidemiology and Distribution

From 1884 to 1996, there were more than 60 reported fatalities from box jellyfish stings in Australia. There are species of box jellyfish in almost all tropical and subtropical seas, but life-threatening species seem to be restricted to the Indo-Pacific.

Notorious Species

SEA WASP

Found in the coastal waters of Australia and Southeast Asia, sea wasp is the common name for the most dangerous cnidarian: Chironex fleckerii. The largest cubozoan, sea wasps have a bell approximately eight inches (20 centimeters) in diameter and tentacles ranging from a few centimeters to up to 10 feet (three meters). Contact with these animals triggers the most powerful and lethal envenomation process known to science. Sea wasp envenomation causes immediate excruciating pain followed by cardiac failure. Death may occur in as little as three minutes.

Recent studies have identified a component of the venom that drills a hole in red blood cells, causing a massive release of potassium, possibly responsible for the lethal cardiovascular depression. The same study may have also identified a way to inhibit this effect, which in the coming years could prove to be clinically promising.

FOUR-HANDED BOX JELLYFISH

The four-handed box jellyfish (Chiropsalmus quadrumanus) habitat spans from South Carolina to the Caribbean, the Gulf of Mexico and as far south as Brazil. The four-handed box jellyfish can inflict extremely painful stings and is the slightly smaller American cousin to the Australian sea wasp. There is one documented case of a four-year-old boy who was stung in the Gulf of Mexico and died within 40 minutes.

BONAIRE BANDED BOX JELLYFISH

Bonaire banded box jellyfish (Tamoya ohboya) is a relatively unknown, highly venomous species found in the Dutch Caribbean. Since 1989, there have been roughly 50 confirmed sightings primarily in Bonaire with the remainder on the shores of Mexico, St. Lucia, Honduras, St. Vincent and the Grenadines. There have only been three reported cases of envenomation, which lead to intense pain and skin damage; only one case required hospitalization.

IRUKANDJI SYNDROME

Tiny box jellyfish found near Australia, Carukia barnesi et Malo kingi, are responsible for the infamous and extremely painful symptomatic complex known as Irukandji syndrome. These small cubozoans’ bells are only a few millimeters with tentacles up three feet (one meter). Fortunately, fatalities from these smaller species are rare, but stings are extremely painful and can cause systemic symptoms including cardiovascular instability that should prompt immediate medical attention. Survivors have reported a feeling of impending doom, claiming they were certain that they could not survive such intense, generalized pain; however, it is important to emphasize that a single sting should not be fatal.

Though stings from lesser-known species of cubozoans are not necessarily lethal, they can still be very painful. An immediate medical evaluation is always recommended.

Prévention

• Properly research the areas you intend to dive.
• Avoid known box jellyfish habitats if you are not sure the dive site or swimming area is safe. If stung, cardiovascular stability can rapidly deteriorate with very little time for any effective field intervention.
• In Northern Queensland, Australia, net enclosures are placed in the water where box jellyfish are known to be during summer months (November to May), but these cannot guarantee safety.
• Minimize unprotected areas. Always wear full wetsuits, hoods, boots and gloves. Something as simple as nylon pantyhose worn over the skin will prevent jellyfish stings.
• Carry sufficient household vinegar with you to all dive sites.

Premiers soins

If stung by any jellyfish, follow these procedures in this order:

1. Activate local emergency medical services.
2. Monitor victim’s airway, breathing and circulation. Be prepared to perform CPR at any moment (particularly if you suspect box jellyfish).
3. Avoid rubbing the area. Box jellyfish tentacles can be cylindrical or flattened, but they are coated with cnydocites, so rubbing the area or allowing the tentacles to roll over the skin will exponentially increase the affected surface area and the envenomation process.
4. Apply household vinegar to the area. Generously pour or spray the area with vinegar for no less than 30 seconds to neutralize any invisible remnants. You can pour the vinegar over the area or use a spray bottle, which optimizes application. Let the vinegar stand for a few minutes before doing anything else.
   NOTE: This will not do anything to the pain or the venom already injected, but it is intended to stabilize any remaining unfired nematocysts on the diver’s skin before you try to remove them.
5. Wash the area with seawater (or saline). Use a syringe with a steady stream of water to help remove any tentacle remains. Do not rub.
   NOTE: Do not use freshwater; this could cause massive nematocyst discharge.
6. Apply heat. Immerse the affected area in hot water (upper limit of 113°F/45°C) for 30 to 90 minutes. If you are assisting a sting victim, try the water on yourself first to assess tolerable heat levels. Do not rely on the victim’s assessment, as intense pain may impair his ability to evaluate tolerable heat levels. If you cannot measure water temperature, a good rule of thumb is to use the hottest water you can tolerate without scalding. Note that different body areas have different tolerance to heat, so test the water on the same area where the diver was injured. Repeat if necessary. If hot water is not available, apply a cold pack or ice in a dry plastic bag.
   NOTE: Application of heat has two purposes: 1) it may mask the perception of pain; and 2) it may assist in thermolysis. Since we know the venom is a protein that has been superficially inoculated, application of heat may help by denaturing the toxin.
7. Always seek an emergency medical evaluation.

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Cone Snails

Cone snails are marine gastropods characterized by a conical shell and beautiful color patterns. Cone snails possess a harpoon-like tooth capable of injecting a potent neurotoxin that can be dangerous to humans.

Identification and Distribution

There are about 600 different species of cone snails, all of which are poisonous. Cone snails live in shallow reefs partially buried under sandy sediments, rocks or corals in tropical and subtropical waters. Some species have adapted to colder waters.

Mechanism of Injury

Injuries typically occur when the animal is handled. Cone snails administer stings by extending a long flexible tube called a proboscis and then firing a venomous, harpoonlike tooth (radula).

Signes et symptômes

A cone snail sting can cause mild to moderate pain, and the area may develop other signs of acute inflammatory reaction like redness and swelling. Conustoxins affect the nervous system and are capable of causing paralysis possibly leading to respiratory failure and death.

Épidémiologie

The prevalence and incidence of cone snails envenomations is unknown, but it is probably a very rare occurrence in divers and the general population. Shell collectors (professional or amateur) may be at higher risk.

Prévention

If you see a beautiful marine snail that looks like a cone, it is probably a cone snail. It is difficult to tell whether a cone snail inhabits a given shell as they are able to hide inside them. Since all cone snails are venomous, err on the side of safety and do not touch it.

Premiers soins

Unfortunately, there is no specific treatment for cone snail envenomations. First aid focuses on controlling pain, but may not influence outcomes. Envenomation will not necessarily be fatal, but depending on the species, the amount of venom injected, and the victim’s size and susceptibility, complete paralysis may occur and this may lead to death. Cone snail venom is a mixture of many different substances including tetrodotoxin (TTX).

1. Clean the wound with freshwater and provide care for a small puncture wound.
2. Apply the pressure immobilization technique.
   NOTE: Application of heat might help with pain management, but since TTX is a heat-stable toxin, the application of heat will not denature the toxin.
3. Watch for signs and symptoms of progressive paralysis.
   • Be prepared to provide mechanical ventilations with a bag valve mask device or a manually triggered ventilator.
   • Do not wait for signs and symptoms of paralysis. Always seek an evaluation at the nearest emergency department.
     NOTE: The bite site might be painless and still be lethally toxic.

Suivant : Chapter 2 – Traumatic Injuries and Complications >

“Wash thoroughly, use soap and keep it clean and dry.”

Bites account for the majority of marine life associated trauma. Fortunately, serious encounters are extremely rare. Traumatic injuries are usually the result of an animal’s defensive reaction to a perceived threat or misidentification of a diver’s body part as a food source. Most puncture wounds do not contain venom and are, therefore, a traumatic injury. Bleeding is the most common acute complication to trauma, while infections are the most common secondary complication. In this chapter, we will cover the more common traumatic injuries, how to prevent them and how to properly manage them.

Dans ce chapitre, vous apprendrez ce qui suit :

• Skin Abrasions
• Stingrays
• Sea Urchins

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Skin Abrasions

An abrasion is a superficial scrape that occurs when the skin is rubbed or bumped against a rough object.

Épidémiologie

Skin abrasions, minor skin cuts and scrapes are very common among recreational divers. Accidental contact with rocks, corals, wrecks and other hard surfaces in or around dive sites can cause injury. Divers with poor buoyancy control frequently report abrasions. In addition, divers who dive close to the bottom or through narrow passageways without the protection of full-length wetsuits often report minor abrasions on their lower extremities.

Risks to Divers

Skin abrasions expose your underlying tissues to microorganisms, significantly increasing the risk of infections. Bleeding can also be of concern, particularly when the injury occurs on highly perfused areas like your face, head, hands and fingers.

Prévention

To avoid skin abrasions, you must master buoyancy control and use mechanical protection like gloves and full-body wetsuits. Though thermal insulation may not be necessary in tropical dive destinations, protection from potential skin abrasions as well as from stinging microscopic life is always a good idea. It is important to note that in an attempt to protect underwater fauna, gloves might not be permitted at some dive destinations. Ask the local dive operator about its protocols before wearing gloves; it may help to explain your reasons for wanting to wear them.

Premiers soins

In case of minor skin abrasions, follow these basic first aid guidelines:

1. Wash the area thoroughly with clean freshwater (sterile if available).
2. Apply antiseptic solution (iodine-based antiseptic solutions may be contraindicated in patients with hyperthyroidism).
3. Control bleeding by applying direct pressure with a sterile bandage.
   • If bleeding has been controlled:
     • Let the area dry out.
     • Apply triple antibiotic ointment.
     • Cover the area with a sterile bandage.
     • Have the wound evaluated by a medical professional within 24 hours to assess risk of infections.
   • If bleeding persists:
     • Cover the wound with clean dressings and keep them in place.
     • Continue to apply pressure.
     • Seek an immediate medical evaluation.

Traitement

For abrasions or amputations with significant bleeding, contact local emergency medical services immediately, apply bleeding control techniques and monitor the patient’s vital signs. Be prepared to manage shock.

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Stingrays

Stingrays are shy, peaceful fish. They do not represent a threat to divers unless startled, stepped on or deliberately corralled and threatened. Most injuries occur in shallow waters when divers or swimmers are walking in areas where stingrays reside.

Biology and Identification

Rays are closely related to sharks: class Chondrichthyes, chondr- meaning cartilaginous and -ichthyes meaning fish. It’s important to note that not all rays have stingers. Stingrays are a specific group of rays classified in the suborder Myliobatoidei, which consists of eight families: deep water stingrays, sixgill stingrays, stingarees, round rays, butterfly rays, river stingrays, eagle rays and whiptail stingrays.

The approximate stingray wingspan varies across species from one foot to more than six feet (two meters). Some freshwater species can weigh up to 1,300 pounds (600 kilograms).

Distribution

There are species of stingrays in nearly all oceans. Some families consist of only freshwater species, which are typically found in tropical, subtropical and temperate river environments.

Mechanism of Injury

Stingrays are not aggressive by any means, and injuries are rarely fatal. The stingray’s defense mechanism consists of a serrated barb at the end of its tail with venom glands located at the base of the barb. The venom is a variable mixture of substances, none of which are specific to the animal; therefore, the creation of antivenom is not possible. Stingrays will strike when threatened or stepped on. The barb can easily tear wetsuits and penetrate skin, and may cause deep, painful lacerations.

Épidémiologie

It is estimated that stingrays are responsible for approximately 1,500 accidents each year in the United States. Prevalence on other countries might be higher, particularly injuries associated with freshwater species, but epidemiological data is either elusive or inexistent.

Signes et symptômes

Stingrays can inflict mild to severe puncture wounds or lacerations. The initial symptom is pain, which can be significant and intensify over several hours. Both puncture wounds and lacerations can damage major blood vessels causing severe, potentially life-threatening bleeding. The barb usually breaks off and may require professional surgical care.

It is common for stingray wounds to become infected despite proper care. Notable possible infections include cellulitis, myositis, fasciitis and tetanus.

Prévention

• Avoid stepping in murky or low-visibility shallow waters where stingrays naturally inhabit.
• Stingrays often burrow in the sand, making them difficult to see even in tropical waters.
• If you are shore diving and you suspect there may be stingrays, carefully shuffle your feet while entering or exiting the water. This technique is known as the “stingray shuffle.” Stingrays are very sensitive animals, and the vibrations caused by this shuffling may scare them away.

Premiers soins

1. Clean the wound thoroughly.
2. Control bleeding if necessary.
3. Do not delay professional medical evaluation. The risk for tetanus and other serious infections must be professionally minimized.

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Sea Urchins

Sea urchins are typically small, rounded spiny creatures found on shallow rocky marine coastlines. The primary hazard associated with sea urchins is contact with their spines.

Biology and Identification

Sea urchins are echinoderms, a phylum of marine animals shared with starfish, sand dollars and sea cucumbers. Echinoderms are recognizable, because their pentaradial symmetry (they have five rays of symmetry), which is easily observed on a starfish. This symmetry corresponds with a water vascular system used for locomotion, transportation of nutrients and waste, and respiration. Sea urchins have tubular feet called pedicellariae, which enable movement. In one genus of sea urchin— the Flower Sea Urchin—some of the pedicellariae have evolved into toxic claws. In this species, the spines are short and harmless, but these toxic claws can inflict an envenomation.

Sea urchins feed on organic matter in the seabed. Their mouth is located on the base of their shell and their anus is on the top. The color of sea urchins varies depending on the species—shades of black, red, brown, green, yellow and pink are common.

Distribution

There are species of sea urchins in all oceans from tropical to arctic waters. Most human-sea urchin incidents occur
in tropical and subtropical waters.

Mechanism of Injury

Sea urchins are covered in spines, which can easily penetrate divers’ boots and wetsuits, puncture the skin and break off. These spines are made of calcium carbonate, the same substance that comprises eggshells. Sea urchin spines are usually hollow and can be fragile, particularly when it comes to extracting broken spines from the skin. Injuries usually happen when people step on them on while walking across shallow rocky bottoms or tide pools. Divers and snorkelers are often injured while swimming on the surface in shallow waters as well as when entering or exiting the water from shore dives.

Épidémiologie

Although little epidemiological data is available, sea urchin puncture wounds are common among divers, particularly when in shallow waters, near rocky shores or in close proximity to wrecks and other hard surfaces. The DAN Medical Information team receives at least one call a week regarding sea urchin injuries, typically from divers and snorkelers swimming in very shallow waters near rocky shores.

Signes et symptômes

Injuries are typically in the form of puncture wounds, often multiple and localized. Skin scrapes and lacerations are also possible. Puncture wounds are generally painful and associated with redness and swelling. Pain ranges from mild to severe depending on several factors, including the species, the body area of the wound, joint or muscular layers compromised, number of punctures, depth of puncture, and the individual’s threshold for pain. Multiple puncture wounds may cause limb weakness or paralysis, particularly with the long-spined species of the genus Diadema. On very rare occasions, immediate life-threatening complications may occur.

Prévention

1. Be observant while entering or exiting the water from shore dives, particularly when the bottom is rocky.
2. If swimming, snorkeling or diving in shallow waters, near rocky shores or in close proximity to wrecks and other hard surfaces, maintain a prudent distance and buoyancy control.
3. Avoid handling these animals.

Premiers soins

There is no universally accepted treatment for sea urchin puncture wounds. Both first aid and definitive care is symptomatic.

1. Apply heat. Immerse the affected area in hot water (upper limit of 113°F/45°C) for 30 to 90 minutes. If you are assisting a sting victim, try the water on yourself first to assess tolerable heat levels. Do not rely on the victim’s assessment, as pain may impair his ability to evaluate tolerable heat levels. If you cannot measure water temperature, a good rule of thumb is to use the hottest water you can tolerate without scalding. Note that different body areas have different tolerance to heat, so test the water on the same area where the diver was injured. Repeat if necessary.
   NOTE: Very few species of sea urchins contain venom. If present, hot water immersion may also help denature any superficial toxins.
2. Remove any superficial spines. Tweezers can be used for this purpose; however, sea urchin spines are hollow and can be very fragile when grabbed from the sides. Your bare fingers are a softer alternative to hard tweezers.
   NOTE: Do not attempt to remove spines embedded deeper in the skin; let those be handled by medical professionals. Deeply embedded spines may break down into smaller pieces, complicating the removal process.
3. Wash the area thoroughly, but avoid forceful rubbing and scrubbing if you suspect there may still be spines embedded in the skin.
4. Apply antiseptic solutions or over-the-counter antibiotic ointments if available.
5. Do not close the wound with tape or glue; this might increase the risk of infection.
   NOTE: Deep puncture wounds are the perfect environment to culture an infection, particularly tetanus.
6. Regardless of any first aid provided, always seek a professional medical evaluation.

Traitement

Contrary to popular belief, very few species of sea urchins are actually toxic. Pain and swelling is often the result of
the body’s reaction to myriad different antigens present on the surface of the spines.

Spines are usually covered with strong pigments, so individual puncture wounds are often clearly visible and may
cause suspicion that each puncture contains a fragment of a spine. Though this is possible, it may not necessarily be
the case. It is easier to assess each individual puncture once the acute inflammatory process has started to recess.

The decision of whether or not surgical removal of retained spines is necessary is usually based on joint or muscular
layer involvement, and whether there is pain with movement or signs of infection. Spines will usually encapsulate in a
short time, but they may not always dissolve. A reactive granuloma is a common reaction to remaining small foreign
bodies. Radiological localization, fluoroscopy or an ultrasound might be useful to avoid a blind surgical extraction
that may cause further spine fracture.

The use of anti-inflammatories and physical therapy is often key for managing these injuries, particularly when they
involve small joints as a prolonged inflammatory process may result in fibrosis, which may limit range of motion.
If signs of infection are present, the doctor may prescribe antibiotics and a tetanus booster.

Flower Sea Urchin

The Flower Sea Urchin (Toxopneustes spp.) is the most toxic of all sea urchins. Its short spines are harmless, but its pedicellariae, which look like small flowers, are tiny claws (Toxopnueustes, meaning toxic foot). These claws contain a toxin that can cause severe pain similar to that of a jellyfish sting, faint giddiness, difficulty breathing, slurred speech, generalized weakness, and numbness of the lips, tongue and eyelids.

Suivant : Chapter 3 – Seafood Poisonings >

“Know what you are eating.”

Les intoxications par les produits de la mer sont des maladies causées par l'ingestion d'une toxine naturelle présente dans les produits de la mer. Cette toxicité peut être inhérente à l'espèce, comme c'est le cas pour le fugu et d'autres tétraodontiformes, ou résulter d'une contamination externe, comme c'est le cas pour les intoxications par les coquillages ou la ciguatera. De nombreux problèmes gastro-intestinaux communément attribués aux intoxications par les fruits de mer sont en réalité le résultat d'infections gastro-intestinales causées par l'ingestion de bactéries, de parasites ou de virus nocifs, et pour cette raison, ils ne sont pas inclus dans ce texte.

Dans ce chapitre, nous aborderons l'ichtyosarcotoxisme, une forme d'intoxication alimentaire résultant de l'ingestion de chair de poisson contenant des toxines naturelles. L'ichtyosarcotoxisme provient des mots grecs ichthyo (poisson), sarx (chair) et toxisme (intoxication ou empoisonnement). Les trois principaux ichtyosarcotoxismes sont la ciguatera, l'intoxication par les poissons scombroïdes et le tétrodotoxisme. Nous aborderons également les intoxications liées aux mollusques. Les coquillages étant des mollusques bivalves et non des poissons, ces cas ne peuvent être qualifiés d'ichtyosarcotoxisme.

En savoir plus :

• Ciguatera
• Empoisonnement des poissons par les scombridés
• Marée rouge et intoxications par les coquillages

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Ciguatera

L'intoxication par la ciguatera se produit lorsque des poissons de récifs contaminés sont consommés. Certains poissons de récifs bioaccumulent des toxines produites par des micro-organismes présents dans leur alimentation. Bien que l'intoxication à la ciguatera ne soit pas mortelle, il n'existe aucun traitement. Il est donc prudent de se familiariser avec les espèces potentiellement toxiques afin d'éviter cette intoxication.

Source d'intoxication

La ciguatera est due à l'ingestion de poissons contaminés par certaines toxines connues sous le nom de ciguatoxines, produites par des dinoflagellés unicellulaires photosynthétiques (Gambierdiscus toxicus) qui font partie du phytoplancton. Les dinoflagellés sont des épiphytes, ce qui signifie qu'ils vivent sur les macroalgues et les surfaces coralliennes mortes. Les petits poissons de récifs se nourrissent de ces coraux et macroalgues et ingèrent accidentellement ces dinoflagellés. Lorsque ces petits poissons sont mangés par des prédateurs plus grands, la toxine est transmise le long de la chaîne alimentaire et s'accumule dans les tissus des prédateurs supérieurs par un processus connu sous le nom de bioaccumulation. L'intoxication humaine peut potentiellement se produire lors de la consommation de n'importe quel poisson impliqué dans cette chaîne, mais l'intoxication est beaucoup plus probable lors de la consommation des plus grands prédateurs.

Les espèces connues pour être une source d'intoxication sont les barracudas, les vivaneaux, les murènes, les poissons-perroquets, les mérous, les balistes et les sérioles, mais d'autres espèces sont connues pour être à l'origine d'épidémies occasionnelles. Les toxines de la ciguatera contaminent rarement les poissons pélagiques tels que le thon, les marlins, les coryphènes ou d'autres poissons à nageoires rayonnées. La ciguatoxine est présente dans le monde entier dans la ceinture de récifs tropicaux située entre 35 degrés de latitude nord et 35 degrés de latitude sud.

Épidémiologie

La ciguatera est probablement le type d'intoxication alimentaire marine le plus courant. Elle est endémique en Australie, dans les Caraïbes et dans les îles du Pacifique Sud. Les cas de ciguatera devraient naturellement se limiter à ces régions, mais en raison des importations commerciales, des cas de ciguatera ont été signalés dans des régions comme St. Louis, Missouri et New York City.

Environ 50 000 cas d'empoisonnement à la ciguatera sont signalés chaque année dans le monde. Les données épidémiologiques concernant l'empoisonnement à la ciguatera sont difficiles à collecter ; en raison du large éventail de symptômes, la ciguatera est souvent mal diagnostiquée ou non diagnostiquée. Les personnes vivant dans les zones endémiques négligent souvent l'évaluation médicale, tandis que les cas importés ne sont probablement pas diagnostiqués ou signalés, car les médecins en dehors des régions endémiques peuvent ne pas être familiarisés avec les symptômes d'une toxine tropicale. Des études récentes ont suggéré que l'incidence de cette maladie continue d'augmenter, bien que cela puisse être dû à une augmentation des déclarations plutôt qu'à une augmentation de l'occurrence de la maladie.

Signes et symptômes

La toxicité dépend de l'exposition et de la dose (quantité ingérée). Les symptômes apparaissent généralement deux à six heures après l'ingestion. Les symptômes peuvent durer des semaines, voire des années et, dans certains cas, entraîner une incapacité à long terme.

Les signes et les symptômes peuvent être très variables, mais comprennent généralement des manifestations neurologiques ou gastro-intestinales ; environ 80 % des patients présentent des degrés variables d'atteinte dans les deux systèmes. Les manifestations les plus courantes sont les suivantes

• Des symptômes gastro-intestinaux tels que des douleurs abdominales et une gastro-entérite, des nausées, des vomissements ou des diarrhées. Ces symptômes initiaux disparaissent généralement sans intervention en quelques heures.
• Les symptômes neurologiques comprennent la paresthésie (picotements et engourdissements), l'ataxie (mouvements musculaires non coordonnés) et le vertige. Les cas graves peuvent inclure une allodynie au froid (inversion de la température), une sensation de brûlure au contact d'objets froids. Les symptômes neurologiques peuvent persister et sont parfois diagnostiqués à tort comme une sclérose en plaques. Chez les patients ayant des antécédents récents de plongée, de faiblesse musculaire et de douleur, ces symptômes neurologiques peuvent également être des facteurs de confusion pour la maladie de décompression.
• Démangeaisons cutanées pouvant persister pendant des semaines et s'aggraver à la suite d'activités qui augmentent la température de la peau, comme l'exercice physique et la consommation d'alcool.

Prévention

• Évitez de consommer les espèces de poissons communément associées à la ciguatera, notamment le barracuda, le mérou, le vivaneau, le poisson-perroquet, la murène, le baliste et la sériole.
• Ciguatoxin is odorless, tasteless and heat-resistant—it will not taste different, and cooking will not prevent intoxication.
• Bien que le poisson entier contienne des toxines, les concentrations les plus élevées se trouvent généralement dans le foie, les intestins et les gonades.

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Empoisonnement des poissons par les scombridés

L'intoxication par les scombridés est une maladie d'origine alimentaire qui résulte de la consommation de poisson avarié contenant des quantités élevées d'histamine.

Source d'intoxication

De nombreuses espèces de poissons peuvent être impliquées dans une intoxication par les scombridés, notamment le maquereau, le thon, la bonite, le germon, les sardines, les anchois, le mahi-mahi, le sériole, le marlin et le hareng.

If scombroids are poorly refrigerated after being caught, the fish will begin to decompose, and bacteria from the fish’s gastrointestinal tract will invade its flesh. Many fish contain a significant amount of an amino acid called histidine in their flesh. When decomposition begins, the bacteria from the gastrointestinal tract breaks histidine down into histamine (a small nitrogen compound involved in regulation of immune reactions and inflammatory responses). While ingestion of histidine is harmless, ingestion of large quantities of histamine can mimic an allergic reaction.

Épidémiologie

Aux États-Unis et en Europe, l'intoxication par les scombridés représente jusqu'à 40 % des épidémies liées aux produits de la mer. Entre 1998 et 2002, 167 épidémies ont été signalées aux États-Unis, touchant 703 personnes et n'entraînant aucun décès. L'intoxication par le scombroïde peut se produire partout dans le monde où des poissons sensibles sont pêchés. Cette intoxication est plus fréquente lors de la consommation de poissons pêchés à des fins récréatives ou dans le cadre d'opérations à petite échelle ; elle se produit rarement dans le cadre de pêches hautement réglementées.

Signes et symptômes

L'ingestion de grandes quantités d'histamine peut imiter une réaction allergique. Les symptômes peuvent apparaître quelques minutes après l'ingestion, jusqu'à deux heures, et disparaissent généralement dans les 24 heures.

En raison de sa ressemblance avec une réaction allergique et d'une mauvaise connaissance de l'intoxication, l'intoxication par les poissons scombroïdes est souvent diagnostiquée à tort comme une allergie aux fruits de mer. Toute personne présentant des signes et des symptômes compatibles avec des réactions allergiques doit consulter immédiatement un médecin, car les réactions allergiques ou de type allergique peuvent mettre la vie en danger.

Prévention

• Scombroid fish poisoning is entirely preventable by immediately storing fresh fish in coolers or ice containers away from direct sunlight. The Centers for Disease Control and Prevention (CDC) recommends temperatures below 40°F (4.4°C) at all points during the fish supply chain.
• Le poisson affecté peut avoir un goût poivré, mais un goût normal ne garantit pas la sécurité.
• L'histamine étant stable à la chaleur, la cuisson n'empêche pas l'intoxication par le poisson scombroïde.

Traitement

Contrairement aux véritables réactions allergiques, où la source d'histamine est interne, le traitement de l'intoxication par les scombridés ne nécessite pas l'utilisation de corticostéroïdes ou d'adrénaline (épinéphrine). Au lieu de cela, l'intoxication par les scombridés répond très bien aux antihistaminiques oraux, qui donnent généralement des résultats positifs dans les 10 à 15 minutes.

Ne pensez jamais que des antihistaminiques oraux suffisent à contrôler par vous-même un empoisonnement présumé par des poissons scombroïdes. Demandez toujours une évaluation médicale professionnelle et laissez un médecin décider du traitement et du meilleur plan d'action.

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Marée rouge et intoxications par les coquillages

La marée rouge est un terme familier désignant un phénomène spécifique connu sous le nom d'efflorescence algale nuisible. Occasionnellement, de grandes concentrations de micro-organismes aquatiques fleurissent naturellement dans les zones côtières. L'accumulation rapide de fleurs d'eau peut être suffisamment importante pour provoquer une décoloration verte, rouge ou brune des environnements estuariens et d'eau douce.

Les scientifiques déconseillent l'utilisation du terme "marée rouge", car ces phénomènes ne sont pas liés aux mouvements des eaux de marée et ne sont pas nécessairement de couleur rouge ou ne présentent pas de décoloration du tout. Lorsque ces proliférations d'algues sont associées à des toxines potentiellement nocives, une terminologie plus précise et privilégiée est celle de prolifération d'algues nuisibles (HAB).

Impact négatif sur les écosystèmes

Parmi les micro-organismes impliqués, certaines espèces de phytoplancton peuvent être présentes et produire des toxines naturelles nocives qui peuvent se concentrer dans les tissus des organismes filtreurs comme les coquillages et autres mollusques et crustacés. L'ensemble de la chaîne alimentaire peut être affecté et des millions de poissons peuvent en mourir.

Danger pour l'homme

Ces toxines peuvent affecter les pêcheries commerciales et représenter une menace pour la santé publique. Les personnes qui consomment des coquillages contaminés peuvent souffrir de diverses intoxications, dont certaines sont potentiellement mortelles. Les risques liés aux HAB peuvent ne pas se limiter à la consommation de coquillages. Il convient donc d'éviter de récolter tout type de fruits de mer dans les zones où les HAB sont connues pour leur caractère endémique.

Intoxications par les mollusques et crustacés

Shellfish are bivalve (two-part shells) mollusks that capture nutrients by filtering water. During this process, these filter feeders can accumulate toxins and other contaminants. When humans consume these bivalves, they may be poisoned. These toxins are water-soluble and heat- and acid-stable—they are unaltered by ordinary cooking methods. Shellfish poisonings are a group of four different syndromes caused by eating bivalve mollusks contaminated with toxins produced by microscopic algae.

SYNDROMES

Il existe quatre types différents d'intoxications par les mollusques qui sont principalement associés à des mollusques tels que les moules, les palourdes, les huîtres et les coquilles Saint-Jacques.

INTOXICATION PARALYSANTE PAR LES MOLLUSQUES ET LES CRUSTACÉS (IPC)

Ces mollusques peuvent accumuler une toxine appelée saxitoxine, produite par le phytoplancton (dinoflagellés, diatomées et cyanobactéries). Certains mollusques restent toxiques pendant plusieurs semaines, tandis que d'autres peuvent stocker la toxine jusqu'à deux ans.

Les proliférations de PSP sont associées à des proliférations d'algues nuisibles, qui peuvent se produire dans presque tous les océans. La toxine paralysante peut être mortelle, en particulier chez les enfants. Les symptômes peuvent apparaître quelques minutes après l'ingestion et comprennent des nausées, des vomissements, des diarrhées, des crampes abdominales, un engourdissement ou une sensation de brûlure autour de la bouche, des gencives et de la langue, puis au niveau du cou, des bras, des jambes et des orteils. D'autres symptômes peuvent inclure une sécheresse de la bouche, un essoufflement, des troubles de l'élocution et une perte de conscience. Des signes de toxicité et de mortalité sont également observés chez les animaux sauvages.

INTOXICATION AMNÉSIQUE PAR LES COQUILLAGES (ASP)

Ce syndrome rare est causé par la consommation de coquillages contaminés par une toxine appelée acide domoïque produite par certaines diatomées marines.

Les symptômes peuvent apparaître 24 heures après l'ingestion de mollusques contaminés et peuvent inclure des nausées, des vomissements, des diarrhées, des crampes abdominales et une gastrite hémorragique. Les signes neurologiques sont graves et peuvent prendre jusqu'à trois jours pour se développer. Les signes neurologiques comprennent des vertiges, une désorientation, des troubles visuels, une perte de mémoire à court terme, une faiblesse motrice, des convulsions, une augmentation des sécrétions respiratoires et des dysrythmies (battements cardiaques irréguliers) mettant en danger la vie du patient. La mort est rare. Les troubles résultant d'une atteinte permanente du système nerveux central peuvent inclure une perte de mémoire à court terme et une neuropathie périphérique (faiblesse, engourdissement ou douleur résultant d'une atteinte nerveuse).

INTOXICATION DIARRHÉIQUE PAR LES MOLLUSQUES (DSP)

Certains dinoflagellés produisent une toxine connue sous le nom d'acide okadaïque qui peut provoquer un syndrome diarrhéique. Cette toxine peut endommager la muqueuse intestinale en la rendant très perméable à l'eau, ce qui provoque une diarrhée importante ainsi que des nausées, des vomissements et des crampes abdominales.

Les symptômes peuvent apparaître quelques minutes à une heure après l'ingestion de coquillages contaminés et peuvent durer environ un jour. Aucun symptôme potentiellement mortel n'a jamais été enregistré, mais une déshydratation grave peut survenir.

INTOXICATION NEUROTOXIQUE PAR LES MOLLUSQUES (NSP)

La PSN est causée par une toxine appelée brevetoxine, produite naturellement par un dinoflagellé connu sous le nom de Karenia brevis. La brevetoxine peut provoquer divers symptômes neurologiques très similaires à ceux de la ciguatera. La PSN ne met généralement pas la vie en danger, mais l'hospitalisation est recommandée jusqu'à ce que toutes les autres causes possibles aient été écartées. Aux États-Unis et dans le golfe du Mexique, une fleur de Karenia brevis est généralement à l'origine du phénomène connu sous le nom de HAB.

Prévention

Les HAB sont présents dans le monde entier, tuant des millions d'animaux marins et affectant les pêcheries. Avant de récolter vos propres fruits de mer dans les zones côtières, renseignez-vous sur les endroits où des HAB sont susceptibles de se produire et évitez de consommer des coquillages et des poissons que vous avez vous-même pêchés dans des zones connues pour être touchées par des HAB. Les pêcheries commerciales sont généralement plus sûres que les petites pêcheries artisanales.

The National Oceanic and Atmospheric Administration (NOAA) has a NOAA HAB (Red Tide) Watch page on Facebook. This system provides an operational forecast for harmful algal blooms. For those not on Facebook, NOAA’s Tides & Currents portal also provides an Operational Forecast System for HABs.

La Florida Fish and Wildlife Conservation Commission propose une ressource en ligne avec une carte actualisée des comptages de marée rouge dans l'État de Floride.

Suivant : Chapter 4 – Appendix >

“Safety is a consequence of education.”

Le Divers Alert Network encourage les plongeurs de tous les niveaux de certification à suivre une formation aux premiers secours afin d'être prêts à réagir en cas de blessures en plongée, y compris celles liées à la vie marine. Le chapitre suivant détaille certaines des techniques de premiers secours et des traitements mentionnés dans le livre, notamment la thermolyse, les antivenins et la technique d'immobilisation par pression. Toutefois, il est important de souligner que la lecture et la compréhension de ces documents ne remplacent pas la formation aux premiers secours.

Si vous n'avez pas reçu de formation officielle, DAN vous recommande vivement de trouver un instructeur qualifié. Pour trouver un instructeur de premiers secours en cas de blessures causées par des espèces marines dangereuses, visitez le site Web du Annuaire des instructeurs DAN.

Dans ce chapitre, vous apprendrez ce qui suit :

• Thermolyse
• Antivenins
• Technique d'immobilisation par pression

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Thermolyse

La thermolyse décrit l'utilisation de la chaleur pour décomposer des substances (thermo signifiant température, et lyse signifiant décomposition ou destruction). Pour ce faire, on immerge souvent la zone affectée dans de l'eau chaude.

Proteins are essential organic compounds that perform a vast array of functions within living organisms. Most life forms live in temperatures below 122°F (50°C).

Au-delà de cette température, leurs protéines subissent un dépliage irréversible de leur structure biomoléculaire tridimensionnelle. Ce processus, appelé dénaturation des protéines, a des conséquences néfastes sur leur fonction. L'application de chaleur peut dénaturer les venins qui sont composés de protéines, éliminant ainsi leur effet ou réduisant leur puissance.

Technique

The standard recommendations for toxin denaturation as a first aid measure call for immersing the affected area in hot freshwater with an upper limit of 113°F (45°C) for 30 to 90 minutes. This may work reasonably well when the toxin inoculation is skin deep, like a jellyfish sting, but will be less effective when toxins have been inoculated by means of deeper puncture wounds, as is the case of lionfish spines. Though quick reasoning could call for increasing the temperature, applying higher temperatures at skin level in an attempt to reach the desired temperature at a deeper level poses an unacceptable risk of burning the skin. In addition, vasodilatation caused by exposure to elevated temperatures may expedite the onset of absorption and of systemic effects.

Chaque cas est unique et nécessite une estimation de la profondeur à laquelle le venin a été injecté ; pour les inoculations superficielles, l'application de chaleur peut être utile pour gérer la douleur et dénaturer les toxines, alors que pour les inoculations plus profondes, la chaleur ne sert qu'à gérer la douleur.

Considérations sur les risques

If you attempt to use thermolysis as a first aid measure, minimize the risk of local tissue damage to the injured diver by testing the water on yourself first on the same area that the diver is injured. Use the hottest temperatures you can tolerate and avoid scalding. Do not rely on the victim’s assessment, as intense pain may impair his ability to evaluate temperature tolerability.

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Antivenin (Antivenin, Antivenene)

L'antivenin est un produit biologique utilisé dans le traitement des morsures ou des piqûres venimeuses (à ne pas confondre avec l'antidote). Bien que cela soit rare, les plongeurs amateurs peuvent être victimes d'une piqûre venimeuse causée par certains organismes marins, tels que le poisson-pierre ou la méduse-boîte, ce qui nécessite l'utilisation d'un antivenin. Les morsures venimeuses, comme celles des serpents de mer, sont encore plus rares.

Qu'est-ce que l'antivenin ?

Antivenoms are blood-derived biological products developed by injecting an animal—typically a horse, goat or sheep—with sublethal doses of venom. The animal will gradually develop antibodies against the venom, which can then be extracted from its blood as a serum to be administered to humans. Like most blood-derived products, antivenoms require an unbroken cold chain (proper refrigeration from production through storage until administration).

Risques Considérations

Bien qu'elle ne soit généralement pas une préoccupation pour les premiers intervenants, l'administration d'antivenins n'est pas sans risque. L'administration intraveineuse de sérums d'animaux peut provoquer un choc anaphylactique chez les personnes sensibles.

Qu'en est-il des auto-injecteurs d'antivenin ?

Occasionally, DAN is asked about autoinjectors for antivenoms. Conceptually, these antivenom autoinjectors would work similarly to the way epinephrine autoinjectors (like EpiPen®) work for intramuscular administration. Though it is certainly a compelling idea, antivenoms are much more complex blood-derived products than epinephrine. As such, they have a much shorter shelf life and require an unbroken cold chain. In addition, antivenoms are administered intravenously, a skill which is beyond first aid responders. These limiting factors make this idea relatively impractical for field operation.

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Technique d'immobilisation par pression

La technique d'immobilisation par pression est une technique de premiers secours destinée à contenir le venin dans la zone mordue et à l'empêcher de passer dans la circulation centrale, où le venin pourrait affecter les organes vitaux. La technique consiste à exercer une pression pour empêcher le drainage lymphatique et une immobilisation pour empêcher le retour veineux (retour du sang vers le cœur) causé par l'action de pompage des muscles squelettiques.

Technique

Utilisez un bandage élastique et une attelle pour exercer une pression et une immobilisation appropriées. Un tissu non élastique n'est pas idéal car il est difficile d'obtenir une pression optimale.

1. Commencez à bander quelques centimètres au-dessus du point de morsure (entre la morsure et le cœur).
2. Enroulez le bandage autour du membre en faisant des tours qui se chevauchent, en remontant le long du membre puis en redescendant au-delà du point de morsure.
3. L'enveloppe doit être suffisamment serrée pour exercer une pression, mais vous devez conserver une sensibilité et une couleur normales, ainsi qu'un pouls palpable.
4. Utilisez une attelle ou un substitut approprié pour immobiliser le membre.
5. Si possible, maintenez les extrémités supérieures à l'aide d'une écharpe.

La santé cardiovasculaire est un élément essentiel de la sécurité de la plongée sous-marine. Cependant, la santé cardiaque peut se détériorer progressivement avec l'âge et mettre les plongeurs en danger. Ce livre couvre les concepts de base des fonctions cardiaques normales dans les activités physiques, les exigences de la plongée en matière de condition physique, la manière dont les maladies cardiaques peuvent affecter la condition physique en plongée et la manière dont les plongeurs peuvent maintenir leur capacité de condition physique.

In this book, you’ll learn about:

• Chapter 1 – Basics of Your Heart & Circulatory System
  • Comment la plongée affecte-t-elle votre santé et votre système circulatoire ?
  • Santé cardiaque et risque de décès en plongée
  • Comprendre le concept de capacité d'exercice aérobie
  • Les effets du vieillissement sur le système cardiovasculaire
  • Calcul de l'intensité de l'activité physique
  • Recommandations en matière d'activité physique
  • Mise en perspective des risques et des bénéfices de l'activité physique
• Chapter 2 – Risk Factors for Cardiovascular Disease
  • Aperçu des facteurs de risque cardiovasculaire
  • L’hypertension
  • Hyperlipidémie
  • Surcharge pondérale et obésité
  • Syndrome métabolique
• Chapter 3 – Structural Anomalies of the Heart
  • Troubles valvulaires
  • Prolapsus de la valvule mitrale
  • Foramen ovale patent
• Chapter 4 – Ischemic Heart Disease
  • L'athérosclérose
  • Infarctus du myocarde
  • Pontages aorto-coronariens
  • Questions spécifiques aux femmes
• Chapter 5 – Arrhythmias
  • Aperçu des arythmies
  • Syncope
  • Extrasystole
  • Fibrillation auriculaire
  • Arrêt cardiaque soudain
  • Questions relatives aux stimulateurs cardiaques implantés
• Chapter 6 – Pulmonary and Venous Disorders
  • Thrombose veineuse profonde
  • Embolie pulmonaire
  • Œdème pulmonaire d'immersion
• Chapter 7 – Issues Involving Cardiovascular Drugs
  • Antiplaquettaires et anticoagulants
  • Statines
  • Antihypertenseurs
  • Antiarythmiques
• Lectures complémentaires et sources

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Crédits

Rédacteur en chef : Petar Denoble, MD, DSc
Rédacteur en chef : James Chimiak, MD

“By 2050, it is estimated that atrial fibrillation (AFib) will affect between 5.6 million and 12 million Americans.”

The electrical wiring of your heart — which controls the rate at which your heart beats, every minute, hour and day, 365 days a year — is one of the most sophisticated and enduring pieces of nature’s engineering. However, there are some irregularities that can occur in that wiring as well as damage that can be caused by disease, all of which can cause symptoms and increase the risk of premature death. Divers, and any physicians who treat them, should be familiar with arrhythmias and their effects on the safety of scuba divers.

Dans ce chapitre, vous apprendrez ce qui suit :

• Aperçu des arythmies
• Syncope
• Extrasystole
• Fibrillation auriculaire
• Arrêt cardiaque soudain
• Questions relatives aux stimulateurs cardiaques implantés

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Aperçu des arythmies

The term “arrhythmia” (or, sometimes, “dysrhythmia”) means an abnormal heartbeat. It is used to describe manifestations ranging from benign, harmless conditions to severe, life-threatening disturbances of the heart’s rhythm.

A normal heart beats between 60 and 100 times a minute. In well-trained athletes, or even select nonathletic individuals, the heart may beat at rest as slowly as 40 to 50 times a minute. Even entirely healthy, normal individuals experience occasional extra beats or minor changes in their heart’s rhythm. These can be caused by drugs (such as caffeine) or stress or can occur for no apparent reason. Arrhythmias become serious only when they are prolonged or when they do not result in proper contraction of the heart.

Physiologically significant extra heartbeats may originate in the upper chambers of the heart (this is called “supraventricular tachycardia”) or in the lower chambers of the heart (this is called “ventricular tachycardia”). The cause of these extra beats may be a short circuit or an extra conduction pathway in the heart’s wiring, or it may be the result of some other cardiac disorder. People who have episodes or periods of rapid heartbeat are at risk of losing consciousness during such events. Other people have a fairly stable arrhythmia (such as “fixed atrial fibrillation”) but in conjunction with additional cardiovascular disorders or other health problems that exacerbate the effect of their rhythm disturbance. A too-slow heartbeat (or a heart blockage) may cause symptoms, too.

Effet sur la plongée

Serious arrhythmias, such as ventricular tachycardia and many types of atrial arrhythmia, are incompatible with diving. The risk for any person who develops an arrhythmia during a dive is, of course, losing consciousness while underwater. Supraventricular tachycardia, for example, is unpredictable in its onset and may even be triggered simply by immersing one’s face in cold water. Anyone who has had more than one episode of this type of arrhythmia should not dive.

La plupart des arythmies nécessitant un traitement médicamenteux interdisent également à la personne concernée de plonger en toute sécurité. Des exceptions peuvent être faites au cas par cas, en consultation avec un cardiologue et un médecin de plongée.

Toute personne souffrant d'une arythmie cardiaque doit faire l'objet d'une évaluation médicale complète par un cardiologue avant de pratiquer la plongée. Dans certains cas, des études électrophysiologiques peuvent identifier une voie de conduction anormale et le problème peut être corrigé. Récemment, les cliniciens et les chercheurs ont déterminé que les personnes souffrant de certaines arythmies (comme certains types de syndrome de Wolff-Parkinson-White, qui se caractérise par une voie de conduction électrique supplémentaire) peuvent pratiquer la plongée en toute sécurité après une évaluation complète par un cardiologue. De même, dans certains cas, les personnes souffrant d'arythmie auriculaire stable (comme la fibrillation auriculaire non compliquée) peuvent plonger en toute sécurité si un cardiologue détermine qu'elles n'ont pas d'autres problèmes de santé importants.

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Syncope

La syncope est une perte de conscience brutale suivie d'une récupération relativement rapide. Les causes de la syncope peuvent être relativement bénignes ou mettre la vie en danger. Elle est rarement négligée et précipite généralement la consultation d'un professionnel de la santé.

Les syncopes qui se produisent dans ou autour de l'eau posent des problèmes particuliers. La noyade survient souvent lorsqu'un plongeur perd connaissance et reste dans l'eau. Une réponse rapide est nécessaire pour ramener un plongeur inconscient à la surface et éviter qu'il ne meure. La syncope peut également survenir à la sortie de l'eau, en raison de facteurs tels que l'effort, la déshydratation et le retour normal du volume sanguin dans les extrémités inférieures.

La réponse initiale à une syncope doit se concentrer sur l'ABC de la réanimation de base : voies respiratoires, respiration et circulation. Une assistance cardiaque avancée peut s'avérer nécessaire. Souvent, le fait de placer les patients syncopaux sur le dos dans un environnement frais leur permet de reprendre rapidement conscience. Si une syncope survient après une plongée, il est important d'envisager la maladie de décompression, la surinflation pulmonaire et l'œdème pulmonaire d'immersion en plus des causes habituelles de l'affection. Bien que la syncope et l'arrêt cardiaque entraînent tous deux une perte de conscience, il est généralement possible de les différencier clairement.

The list of possible causes of syncope is extensive, but a good medical history can help eliminate the majority of them. The patient’s age, heart rate, family history, medical conditions and medications are key in identifying the cause. If syncope is accompanied by convulsions (known as “tonic-clonic movements”), it may have been precipitated by a seizure. If it occurs upon exertion, a serious cardiac condition may be preventing the heart from keeping up with the demands of the physical activity; chest pain may be associated with this type of syncope. If standing up quickly results in syncope, that points to a cause known as “orthostatic hypotension.” And pain, fear, urination, defecation, eating, coughing or swallowing may cause a variation of the condition known as “reflex syncope.”

A medical evaluation after an incident of syncope should include a thorough history and physical — plus interviews with witnesses who observed the individual’s collapse and who can accurately relay the sequence of events. A few cases may require more extensive investigation, and some result in no conclusion.

Effet sur la plongée

While a medical evaluation is being conducted, it is recommended that the affected individual refrain from any further diving. The cause of a given syncopal episode can be elusive but must be pursued — especially if the individual hopes to return to diving. Once the underlying factors have been determined, a diving medical officer and appropriate specialists should consider whether diving can be resumed safely.

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Extrasystole

Heart beats that occur outside the heart’s regular rhythm are known as “extrasystoles.” They often arise in the ventricles, in which case they are referred to as “premature ventricular contractions” or sometimes “premature ventricular complexes,” abbreviated as PVCs. The cause of such extra beats can be benign or can result from serious underlying heart disease.

Les PVC sont fréquents même chez les personnes en bonne santé ; ils ont été enregistrés chez 75 % des personnes soumises à une surveillance cardiaque prolongée (c'est-à-dire pendant au moins 24 heures). L'incidence des PVC augmente également avec l'âge ; elles ont été enregistrées chez plus de 5 % des personnes âgées de plus de 40 ans qui subissent un électrocardiogramme (ou ECG, un examen qui prend généralement moins de 10 minutes). Les hommes semblent plus touchés que les femmes.

The extrasystole itself is usually not felt. It is followed by a pause — a skipped beat — as the heart’s electrical system resets itself. The contraction following the pause is usually more forceful than normal, and this beat is frequently perceived as a palpitation — an unusually rapid or intense beat. If extrasystoles are either sustained or combined with other rhythm abnormalities, affected individuals may also experience dizziness or lightheadedness. Heart palpitations and the sensation of missed or skipped beats are the most common complaints of those who seek medical care for extrasystole.

A medical examination of the condition begins with a history and physical and should also include an ECG and various laboratory tests, including the levels of electrolytes (such as sodium, potassium and chloride) in the blood. In some cases, doctors may recommend an echocardiogram (an ultrasound examination of the heart), a stress test and/or the use of a Holter monitor (a device that records the heart’s electrical activity continuously for a 24- to 48-hour period). Holter monitoring may uncover PVCs that are unifocal — that is, they originate from a single location. Of greater concern are multifocal PVCs — those that arise from multiple locations — as well as those that exhibit specific patterns known R-on-T phenomenon, bigeminy and trigeminy.

If serious structural disorders, such as coronary artery disease or cardiomyopathy (a weakening of the heart muscle), can be ruled out — and the patient remains asymptomatic — the only “treatment” required may be reassurance. But for symptomatic patients, the course is less clear, as there is controversy regarding the effectiveness of the available treatment options. Two drugs commonly used to treat high blood pressure — beta blockers and calcium channel blockers — have been used in patients with extrasystole with some success. Antiarrhythmics have also been prescribed for extrasystole but have met with mixed reviews. A procedure known as cardiac ablation may be an option for symptomatic patients, if the location where their extra beats arise can be identified; the procedure involves threading tiny electrodes into the heart via catheters, then zapping the affected locations to rewire the heart’s faulty circuits.

Effet sur la plongée

Bien que les PVC soient présents chez un grand pourcentage d'individus par ailleurs normaux, il a été démontré qu'ils augmentent la mortalité au fil du temps. Si des PVC sont détectées, il est important de les examiner et d'exclure les pathologies associées connues. Les plongeurs qui souffrent de PVC et dont on découvre qu'ils sont également atteints d'une maladie coronarienne ou d'une cardiomyopathie s'exposent à un risque important s'ils continuent à plonger. Les plongeurs chez qui l'on a diagnostiqué un phénomène R-on-T, des épisodes non soutenus de tachycardie ventriculaire ou des PVC multifocales doivent également s'abstenir de plonger. Les plongeurs qui présentent des PVC mais qui restent asymptomatiques peuvent envisager de reprendre la plongée ; ces personnes doivent discuter avec leur cardiologue de leurs résultats médicaux, de leur désir de continuer à plonger et de leur bonne compréhension des risques encourus.

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Fibrillation auriculaire

Atrial fibrillation (AF or AFib), the most common form of arrhythmia, is characterized by a fast and irregular heartbeat. It results from a disturbance of the electrical signals that normally make the heart contract in a controlled rhythm. Instead, chaotic and rapid impulses cause uncoordinated atrial filling and ventricle pumping action. This leads to a decrease in overall cardiac output, which can affect one’s exercise capacity or even result in unconsciousness. In addition, AF causes blood to pool in the atria, which promotes the formation of blood clots that may break loose and enter the circulatory system; if this occurs, it may result in a stroke.

Des études américaines récentes ont montré une augmentation de l'incidence globale de la FA ainsi que des différences raciales significatives dans sa prévalence. Le risque de FA au cours de la vie (à l'âge de 80 ans) a récemment été évalué à 21 % chez les hommes blancs et à 17 % chez les femmes blanches, mais à seulement 11 % chez les Afro-Américains des deux sexes. D'ici 2050, on estime que la FA touchera entre 5,6 et 12 millions d'Américains. Ces chiffres sont significatifs, car la FA est associée à un risque quatre à cinq fois plus élevé d'accident vasculaire cérébral ischémique. Après ajustement des autres facteurs de risque, les personnes souffrant de FA ont également un risque de démence deux fois plus élevé.

The most common causes of AF are hypertension and coronary artery disease. Additional causes include a history of valvular disorders, hypertrophic cardiomyopathy (a thickening of the heart’s muscle), deep vein thrombosis (DVT), pulmonary embolism, obesity, hyperthyroidism (also called “overactive thyroid”), heavy alcohol consumption, an imbalance of electrolytes in the blood, cardiac surgery and heart failure.

Some people with AF experience no symptoms and are unaware they have the condition until it’s discovered during a physical examination. Others may experience symptoms such as the following:

• Palpitations (battements de cœur rapides, inconfortables et irréguliers ou sensation de basculement dans la poitrine)
• Faiblesse
• Diminution de la capacité à faire de l'exercice
• Fatigue
• Étourdissements
• Vertiges
• Confusion
• Essoufflement;
• Douleur thoracique

L'apparition et la durée de la fibrillation auriculaire s'inscrivent généralement dans l'un des trois schémas suivants :

• Occasional (or “paroxysmal”): Le trouble du rythme et ses symptômes vont et viennent, durant quelques minutes à quelques heures, puis s'arrêtent d'eux-mêmes. Ces événements peuvent se produire quelques fois par an et leur fréquence augmente généralement avec le temps.
• Persistant : The heart’s rhythm doesn’t go back to normal on its own, and treatment — such as an electrical shock or medication — is required to restore a normal rhythm.
• Permanent : The heart’s rhythm can’t be restored to normal. Treatment may be required to control the heart rate, and medication may be prescribed to prevent the formation of blood clots.

Tout nouveau cas de FA doit faire l'objet d'une investigation afin d'en déterminer la cause. L'examen peut comprendre un examen physique, un électrocardiogramme, une mesure des niveaux d'électrolytes, y compris le magnésium, un dosage des hormones thyroïdiennes, un échocardiogramme, une numération sanguine complète et/ou une radiographie du thorax.

Treating the underlying cause of AF can help control the fibrillation. Various medications, including beta blockers, may help regulate the heart rate. A procedure known as cardioversion — which can be performed with either a mild electrical shock or medication — may prompt the heart to revert to a normal rhythm; before cardioversion is attempted, it is essential to ensure that a clot has not formed in the atrium. Cardiac ablation, which is described in the “Extrasystole” section, may also be used to treat AF. In addition, anticoagulant drugs are often prescribed for individuals with AF to prevent the formation clots and thus reduce their risk of stroke. It is also of note that the neurological effects of an embolic stroke associated with AF can sometimes be confused with the symptoms of decompression sickness.

Effet sur la plongée

A thorough medical examination should be conducted to identify the underlying cause of the atrial fibrillation. It is often the underlying cause that is of most concern regarding fitness to dive. But even atrial fibrillation itself can have a significant impact on cardiac output and therefore on maximum exercise capacity. Individuals who experience recurrent episodes of symptomatic AF should refrain from further diving. The medications often used to control atrial fibrillation can present their own problems, by causing other arrhythmias and/or impairing the individual’s exercise capacity. It is essential that anyone diagnosed with AF have a detailed discussion with a cardiologist before resuming diving.

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Arrêt cardiaque soudain

Sudden cardiac arrest (SCA) — a cessation of the heart’s beating action, with little or no warning — is an acute medical emergency. During the arrest, blood stops circulating to the body’s vital organs, including the brain, the kidneys and the heart itself. Cut off from oxygen, these organs die within minutes. If the arrest is not corrected quickly, the affected individual will not survive.

The causes of SCA include myocardial infarction (heart attack), heart failure, drowning, coronary artery disease, electrolyte abnormalities, drugs, abnormalities in the heart’s electrical conduction system, cardiomyopathy (a weakening of the heart muscle) and embolism (a clot that has lodged in a major vessel).

L'ACS est responsable de 450 000 décès aux États-Unis chaque année et de 63 % des décès cardiaques chez les Américains de plus de 35 ans. Le risque de mort subite d'origine cardiaque chez l'adulte est multiplié par six avec l'âge, parallèlement à l'augmentation de l'incidence des cardiopathies ischémiques. Le risque d'ACS est plus élevé chez les personnes souffrant de maladies cardiaques structurelles, mais dans 50 % des cas de mort subite d'origine cardiaque, la victime n'avait pas conscience d'être atteinte d'une maladie cardiaque, et dans 20 % des autopsies réalisées à la suite de ces décès, aucune anomalie cardiovasculaire structurelle n'a été trouvée.

Bien qu'il n'y ait généralement pas de signes avant-coureurs d'un arrêt cardiaque soudain, la personne peut parfois ressentir des étourdissements, des difficultés respiratoires, des palpitations ou des douleurs thoraciques.

Le traitement immédiat doit être axé sur le rétablissement rapide de la circulation à l'aide de compressions thoraciques ou d'une réanimation cardio-pulmonaire et d'une défibrillation. Après la réanimation, la victime doit être transportée à l'hôpital dès que possible. Le traitement ultérieur peut consister en des efforts pour éliminer la cause sous-jacente de l'arrêt par l'administration de médicaments, la chirurgie ou l'utilisation de dispositifs électriques implantés.

Les stratégies préventives consistent à apprendre à reconnaître les signes avant-coureurs de l'ACS, au cas où ils se produiraient ; à identifier, éliminer ou contrôler tout facteur de risque susceptible de vous affecter ; et à programmer des examens physiques réguliers, ainsi que les tests appropriés, lorsqu'ils sont indiqués.

Effet sur la plongée

Les plongeurs présentant des symptômes de maladie cardiovasculaire doivent être évalués par un cardiologue et un spécialiste de la médecine de plongée quant à la poursuite de leur activité. Chez les personnes asymptomatiques, le risque de MSC peut être évalué à l'aide des facteurs de risque cardiovasculaire connus tels que le tabagisme, l'hypertension artérielle, l'hypercholestérolémie, le diabète, le manque d'exercice et le surpoids. Par exemple, les fumeurs ont deux fois et demie plus de risques de souffrir d'une mort cardiaque subite que les non-fumeurs.

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Questions relatives aux stimulateurs cardiaques implantés

A pacemaker is a small battery-operated device that helps an individual’s heart beat in a regular rhythm. It does this by generating a slight electrical current that stimulates the heart to beat. The device is implanted under the skin of the chest, just below the collarbone, and is hooked up to heart with tiny wires that are threaded into the organ through its major vessels. In some individuals, the heart may need only intermittent help from the pacemaker, if the pause between two beats becomes too long. In others, however, the heart may depend completely on the pacemaker for regular stimulation of its beating action.

Effet sur la plongée

Chaque cas de stimulateur cardiaque doit être évalué individuellement. Les deux facteurs les plus importants à prendre en compte sont les suivants :

1. Pourquoi la personne est-elle dépendante d'un stimulateur cardiaque ?
2. Is the individual’s pacemaker rated to perform at depths (in other words, pressures) compatible with recreational diving — plus an added margin of safety?

La raison de ce deuxième facteur est qu'un stimulateur cardiaque est implanté dans des tissus situés juste sous la peau et qu'il est donc exposé, pendant la plongée, aux mêmes pressions ambiantes que le plongeur. Pour une plongée en toute sécurité, un stimulateur cardiaque doit être conçu pour fonctionner à une profondeur d'au moins 40 mètres et doit également fonctionner de manière satisfaisante dans des conditions de changements de pression relativement rapides, comme c'est le cas lors de la remontée et de la descente.

As with any medication or medical device, the underlying problem that led to the implantation of the pacemaker is the most significant factor in determining someone’s fitness to dive. The need to have a pacemaker implanted usually indicates a serious disturbance in the heart’s own conduction system.

Si la perturbation provient d'une lésion structurelle du muscle cardiaque lui-même, comme c'est souvent le cas lorsqu'une personne est victime d'une crise cardiaque majeure, il se peut que la personne n'ait pas la capacité cardiovasculaire nécessaire pour plonger en toute sécurité.

Toutefois, certaines personnes dépendent d'un stimulateur cardiaque non pas parce que le muscle cardiaque a été endommagé, mais simplement parce que la zone qui génère les impulsions qui font se contracter le muscle cardiaque ne fonctionne pas de manière cohérente ou adéquate. Ou bien le circuit qui conduit les impulsions au muscle cardiaque peut être défectueux, ce qui se traduit par des signaux incorrects ou irréguliers. Sans l'assistance d'un stimulateur cardiaque, ces personnes peuvent souffrir d'épisodes de syncope (évanouissement). D'autres personnes peuvent avoir subi une crise cardiaque suffisamment légère pour que les dommages résiduels au muscle cardiaque soient minimes, mais leur système de conduction reste peu fiable et a donc besoin d'être stimulé par un stimulateur cardiaque.

If a cardiologist determines that an individual’s level of cardiovascular fitness is sufficient for safe diving, and the individual’s pacemaker is rated to function at a pressure of at least 130 feet (40 meters), that individual may be considered fit for recreational diving. But once again, it cannot be emphasized strongly enough that any divers with cardiac issues check with their doctor before diving.

Suivant : Chapter 6 – Pulmonary and Venous Disorders >

“The risk of a DVT occurring on a flight lasting more than four hours is between 1 in 4,650 flights and 1 in 6,000 flights.”

Your lungs have many functions in your body beyond just oxygenating your blood. One of their other important roles is filtering the venous blood that returns from the body. The venous system is characterized by slower blood flow than the arterial system, which contributes to the occasional formation of a blood clot (known as a “peripheral venous thrombosis”), which could be transported into the lungs and could even cause a pulmonary embolism (or blockage in the vessels of the lungs).

Dans ce chapitre, vous apprendrez ce qui suit :

• Thrombose veineuse profonde
• Embolie pulmonaire
• Œdème pulmonaire d'immersion

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Thrombose veineuse profonde

Deep vein thrombosis (DVT) is a condition in which a blood clot (a “thrombus”) forms in one or more of the body’s deep veins, usually in the legs. If a clot breaks free and travels through the circulatory system, it can lead to life-threatening conditions. For example, if a clot lodges in the lungs, it is known as a pulmonary embolism (PE) and affects the lungs’ ability to oxygenate the blood (see “Pulmonary Embolism”). Collectively, DVT and PE are sometimes referred to as venous thromboembolisms (VTEs).

A clot that originates as a DVT can also cause a stroke in individuals with a patent foramen ovale (PFO, a hole in the wall between the atria — see “Patent Foramen Ovale” for details about this condition); in such a case, the clot travels through the veins to the right atrium of the heart, passes through the PFO to the left atrium and then travels through the arteries to the brain.

La TVP n'est pas liée à la plongée, mais les plongeurs voyagent souvent et les voyages constituent un facteur de risque important pour la TVP. Dans environ la moitié des cas de TVP, l'individu ne présente aucun symptôme notable avant l'apparition de la maladie. Le plus souvent, la maladie se déclare au niveau du mollet. Les symptômes peuvent être les suivants

• Gonflement de la jambe, de la cheville ou du pied affecté
• Douleur dans le mollet qui s'étend à la cheville ou au pied
• Chaleur dans la zone affectée
• A change in the color of the skin — to pale, red or blue

La plupart des TEV liées à un voyage en avion surviennent dans les deux semaines suivant le vol et disparaissent dans les huit semaines. Si elle n'est pas traitée, une TVP qui débute dans le mollet s'étend à la cuisse et au bassin dans environ 25 % des cas. Une TVP de la cuisse et du bassin non traitée a un risque d'environ 50 % de conduire à une EP, qui est la complication la plus grave de la TVP. De nombreux cas de TVP sont asymptomatiques et se résorbent spontanément. Toutefois, la TVP réapparaît souvent chez une personne qui a déjà souffert d'un épisode de la maladie.

Most DVTs occur in individuals with pre-existing risk factors for DVT who remain motionless for a long time — such as when traveling a long distance by plane, car or train; when doing deskwork over a period of many hours; or when bedridden. This is because immobility slows down the blood flow in the veins (a condition known as “venous stasis”); in addition, pressure on the calf from an inadequate seat can injure the vein walls. If you sit still for 90 minutes, the blood flow in your calf drops by half, and that doubles your chance of developing a blood clot. For every additional hour you spend sitting, your risk of a blood clot increases by 10 percent.

The incidence of DVT in the general population is one-tenth of one percent, but it is higher in those who have risk factors and those who travel often. Long-distance air travel may double or even quadruple the risk of suffering a VTE. Although DVT is often called the “economy class disease,” business-class travelers are susceptible, too. The risk of a DVT occurring on a flight lasting more than four hours is between 1 in 4,650 flights and 1 in 6,000 flights; this is lower than the risk in the general population, but that’s because people who take long trips are likely to be healthier than average. The incidence of DVT among travelers with a low to intermediate pre-existing risk for VTE who take a journey longer than eight hours was found to be 0.3 percent for symptomatic cases and 0.5 percent when including asymptomatic cases as well.

Les facteurs de risque de la TVP sont les suivants

• L'âge avancé (le risque augmente après 40 ans)
• Obésité (définie par un indice de masse corporelle supérieur à 30)
• Utilisation d'œstrogènes (contraceptifs hormonaux ou traitement hormonal de substitution)
• Grossesse (y compris la période postnatale)
• Thrombophilie (tendance anormalement élevée du sang à coaguler)
• Antécédents de MTEV ou antécédents familiaux de MTEV
• Cancer actif
• Maladie grave
• Intervention chirurgicale, hospitalisation ou traumatisme récent
• Mobilité limitée
• Central venous catheterization (the presence of a catheter in one’s chest, for use in administering medication or nutrients and/or drawing blood samples)

Entre 75 % et 99 % des personnes qui développent une TEV liée à un voyage présentaient plus d'un de ces facteurs de risque.

Height is also a factor in one’s risk of developing a travel-related DVT. People who are either very short — less than 5 feet, 3 inches (1.6 meters) — or very tall — more than 6 feet, 3 inches (1.9 meters) — appear to be at increased risk as a result of their inability to adjust their seats sufficiently to accommodate their height. In addition to effects of immobility, shorter passengers may suffer greater than usual seat-edge pressure on the backs of their knees, and taller passengers may be cramped due to insufficient leg room. All of these factors can contribute to injury of deep veins, venous stasis and activation of the blood’s clotting mechanisms.

Those who are at increased risk of DVT should wear compression socks whenever they fly or drive long distances and should consult their primary-care provider regarding the possible benefit of taking a clot-preventative such as aspirin. Although the risk of DVT for healthy people is small, everybody should be aware of the factors that can precipitate the condition — and avoid long periods of immobility. The best way to prevent DVT is to get up and walk around from time to time. It also helps to flex your feet and calf muscles regularly if you must remain seated for any length of time. Finally, it is also helpful in preventing DVT to stay well hydrated.

Effet sur la plongée

Toute personne chez qui on a diagnostiqué une TVP aiguë ou qui prend des anticoagulants doit s'abstenir de plonger. Il est possible de reprendre la plongée en toute sécurité après une TVP, mais l'évaluation de l'aptitude à la plongée doit être faite au cas par cas.

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Embolie pulmonaire

A pulmonary embolism (PE) is an obstruction (or “embolus”) that lodges in the vasculature of the pulmonary system, or lungs. The embolus may be air, fat or a blood clot (or “thrombus”). If a PE is caused by a thrombus, the clot typically originated in the deep vein system of the legs — a condition known as deep vein thrombosis (DVT); see “Deep Vein Thrombosis” for a discussion of DVT. The resulting obstruction in the flow of blood to the lungs typically causes a drop in cardiac output and a significant drop in blood pressure.

L'apparition de l'EP peut être aiguë ou chronique. L'EP aiguë provoque souvent des symptômes évidents pour l'individu, tandis que l'EP chronique ne révèle souvent sa présence que par des résultats très subtils qui sont passés inaperçus pour l'individu affecté. Une EP non traitée a un taux de mortalité élevé. Le pronostic est particulièrement sombre pour les personnes qui présentent en même temps une TVP, un thrombus du ventricule droit ou un dysfonctionnement du ventricule droit. On estime que 1,5 % des décès sont diagnostiqués comme étant dus à une EP.

Risk factors for DVT — and thus for PE — include recent surgery; a stroke; a diagnosis of autoimmune disease, malignancy or heart disease; obesity; smoking; hypertension; and a previous DVT.

Symptoms of PE include chest pain (also known as “dyspnea”), pain or swelling of the calf (signaling a DVT), hypotension (abnormally low blood pressure), an altered level of consciousness and syncope (fainting). Distension of the neck veins in the absence of other conditions — such as pneumothorax (a buildup of air in the membrane surrounding the lungs, sometimes referred to as a collapsed lung) or heart failure — may also be observed in individuals suffering a PE.

PE should be one of the first conditions considered when attempting to make a diagnosis in someone exhibiting acute onset of any of the symptoms listed above and any of the associated risk factors. Appropriate diagnostic tests may include measurement of the individual’s levels of a hormone called brain natriuretic peptide (BNP) and of a protein known as cardiac troponin, as well as a CT angiogram of the lungs.

Treatment should focus initially on managing the significant cardiopulmonary impairments that are usually involved in a PE. Such care may include breathing support from an artificial ventilator and fluid management. The use of anticoagulant medication is also important, both to treat the embolus and to stop the development of another thrombus. Thrombolysis (known as “clot-busting”), embolectomy (surgical removal of the embolus) or the placement in the vena cava (one of the large vessels in the chest) of a filter designed to prevent any future clots from reaching the lungs may also be considered — especially in anyone who goes into shock, because mortality in such cases approaches 50 percent. Similar measures may be called for in cases of PE caused by a venous gas bubble. Hyperbaric oxygen therapy may be indicated as well, if the individual’s condition does not improve or deteriorates even after the application of supportive measures.

Effet sur la plongée

Despite many medical advances, five-year all-cause mortality in individuals who have suffered a PE due to underlying risk factors remains more than 30 percent. And pulmonary hypertension — elevated pressure in the arteries that carry blood from the heart to the lungs, a condition that limits one’s exercise capacity — often persists in individuals who have had a PE, even after successful treatment. Thus any determination of fitness for diving by those who have had a PE must include an evaluation of their lung function, underlying conditions, anticoagulation status, exercise capacity and cardiac status.

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Œdème pulmonaire d'immersion

Immersion pulmonary edema (IPE) is a form of pulmonary edema — an accumulation of fluid in the tissues of the lungs — that specifically affects divers and swimmers. Immersion at depth is a key factor in the development of IPE. That’s because immersion in an upright position causes a significant shift of fluid from the peripheral to the central circulatory system, resulting in higher pressure in the capillaries of the pulmonary system. Elements of the diving milieu that contribute to IPE’s occurrence include the fact that divers breathe gases that are denser than air at sea level, which means more negative pressure within chest is needed to inhale; the likelihood of gas bubbles becoming trapped in the vasculature of the lungs; the cold underwater environment; and the potential in underwater settings for exertion or panic, which can exacerbate elevated capillary pressure.

Maintaining a proper fluid balance in your lung tissue and its vasculature requires a dynamic combination of various opposing forces. Unopposed changes in any of these forces can result in a buildup of excess fluid — or edema — in your pulmonary tissue. The main variables involved in regulating this fluid balance are the following:

• Pression oncotique (forme de pression exercée par les protéines) dans les capillaires pulmonaires, les plus petits vaisseaux du système circulatoire.
• Oncotic pressure in the pulmonary system’s interstitial fluid (fluid in the cavities of your lung tissue)
• Perméabilité des capillaires pulmonaires
• Pression hydrostatique (pression d'un fluide au repos) dans les capillaires pulmonaires
• Pression hydraulique (pression d'un fluide comprimé ou pompé) dans le liquide interstitiel
• Pression dans les alvéoles, les minuscules sacs d'air des poumons.

These factors, which collectively are known as “Starling forces,” can all be quantified and placed in an equation that can then be used to calculate the net differential of
les forces.

Pulmonary edema is caused by changes in these forces — such as a drop in the levels of key proteins in the blood; leakage from the pulmonary capillaries due to sepsis (a life-threatening complication of infections); an increase in hydrostatic pressure in the pulmonary capillaries due to heart failure; and negative pressure in the alveoli due to resistance from breathing through a faulty regulator. Additional issues that can contribute to the development of pulmonary edema include side effects of some cardiovascular drugs; ARDS (acute respiratory distress syndrome, a life-threatening condition that prevents oxygen from getting to the lungs); reperfusion (a procedure that restores circulation after a heart attack or stroke); cardiomyopathy (a weakening of the heart muscle); high-altitude pulmonary edema; a pulmonary embolus (a blood clot lodged in a vessel in the lungs); re-expansion (the reinflation of a collapsed lung); pulmonary hypertension (elevated pressure in the arteries that carry blood from the heart to the lungs); lung cancer; hemorrhage (uncontrolled bleeding); and various disorders of the nervous system. Other factors can include overhydration by well-intentioned divers who have heard the conventional wisdom that dehydration is a risk factor for decompression sickness, as well as poor physical conditioning, which can result in increased negative pressure in the alveoli during deep inspiration.

Les symptômes de l'EPI comprennent des douleurs thoraciques, une dyspnée (gêne ou difficulté à respirer), une respiration sifflante et des expectorations roses et mousseuses pendant l'immersion ou peu après la sortie de l'eau. La plupart des personnes qui souffrent d'un épisode d'EPI n'avaient pas d'antécédents ou de signes significatifs indiquant une prédisposition à cette affection ; néanmoins, le risque d'EPI augmente avec l'âge, l'obésité et une pression artérielle élevée.

Once pulmonary edema occurs, hypoxia (lack of an adequate supply of oxygen) leads to constriction of the pulmonary vasculature, which worsens the cascade of ill effects. The situation can be further aggravated by the accompanying dyspnea, which, when experienced underwater, can induce panic and uncontrolled ascent to the surface — leading to overinflation of the lungs and even near-drowning.

To help differentiate immersion pulmonary edema from other conditions with similar symptoms (such as near-drowning, pulmonary decompression sickness and pulmonary overinflation syndrome), it is important to keep in mind that IPE’s onset can occur either at depth or upon reaching the surface. And it is not necessarily precipitated by aggressive diving, a rapid ascent or the aspiration of water.

Treatment for IPE should begin with removal of the affected individual from the water (to relieve the compression of the vessels in the lower extremities, allowing centrally pooled fluids to return to the extremities) and with administration of oxygen (beginning at 100 percent and later at a reduced concentration). A diuretic such as Lasix may help to reduce excess intravascular fluid, although diuresis — the body’s natural excretion of fluid — may already be under way as a result of hormonal influences. The condition usually resolves quickly in a healthy diver. Prolonged hospitalization is rarely required; if it is necessary, it’s usually due to contributing factors, such as an underlying cardiac problem.

Effet sur la plongée

Some divers have one episode of IPE and never experience the condition again, but repeated episodes are likely. Any individuals who suffer a first episode of IPE are advised to undergo a detailed examination to rule out any medical conditions that may have caused the edema and then to have a thorough discussion with their physician regarding the risks of continuing to dive. And all divers are urged to have regular maintenance on their regulators, to refrain from overhydration and to attend to proper dive planning in order to avoid exertion and panic — as well as to keep conditions such as obesity and hypertension under control.

Suivant : Chapter 7 – Issues Involving Cardiovascular Drugs >