Introduction to Dive Medicine

DIVING MEDICINE

Diving Medicine is a growing medical speciality that focuses on the study, diagnosis and treatment of illnesses related to changes in pressure and the undersea environment. This area is rapidly expanding its knowledge base as the popularity of diving and undersea exploration continues to explode. A primary focus of diving medicine is to assess individual "Diving Fitness". As more and more people take to the water, there is an increased need to safely prepare or assess ability to dive among patients with various disease states. Particularly, dive physicians must understand how various ENT, Eye, Heart, Pulmonary, Gastrointestinal, Bone and Joint, Hematologic, Endocrine and Metabolic disease states affect the ability to dive. In addition, dive physicians can offer recommendations for people about flying and altitude, physchology and drugs, dental work, women specific concerns, hazardous marine life, long term effects of diving and specific treatment modalities if an accident occurs.

The primary accidents occuring in diving typically deal with effect pressure has on the various gases in your body. Most dive physicians treat patients for problems with equalizing pressure in their ears, sinus difficulties and of course barotrauma due to rapid ascension - "the bends". While these areas of dive medicine are perhaps most critical to understand in terms of patient care and treatment. I have chosen to speak on the more exotic, but rare, injuries from interactions with marine life.

OVERVIEW OF MARINE HAZARDS

There are a number of hazardous creatures in the sea. Many can cause serious harm to unaware or inattentive divers. Some may even cause death, although this often depends on the amount of venom used, individual reactions, nature of injury and location of accidents (deep water victims often drown). There are four major types of injury patterns from marine life. This presentation will Some basic first aid tips are given, although by far the best policy is not to meddle with these creatures.

Sea Anenomes and Sea Cucumbers

While most sea anemones are relatively harmless to humans a few do contain strong toxic substances producing quite severe effects. One of these is the stinging anemone (Actinodendron plumosum), a blue-grey to light brown animal which can look somewhat like a fir tree.

Found under boulders and coral, red bristle worms have numerous fine needle-like bristles which break off when they have become embedded in the skin, causing severe irritation.

Although sea cucumbers are one of the safest animals on the reef to touch, the numerous white Cuvierian tubules, which some eject when irritated, contain a toxin which can cause blindness if it comes into contact with the eyes. This toxin may also be present on the skin so you should wash your hands after handling these creatures.

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STINGING CORALS

Although known widely as stinging or fire corals, these organisms are, in fact, colonial animals (Millepora sp) more closely related to hydroids. Having a hard coral-like skeleton, they vary in form from large upright sheets and blades to branching, finger-like 'antlers' with a yellow-green to brown colour. Effects and treatment are similar to hydroid stings.

CROWN-OF-THORNS STARFISH

The sharp spines of this creature are covered with a thin venomous skin which, if introduced into any wound can cause nausea, vomiting and swelling. Spines may also break off and remain embedded.

HYDROIDS

Looking like feathery plants, and sometimes referred to as fireweed, hydroids are actually colonies of animals equipped with strong stinging cells (nematocysts) used to capture prey and for defence. Some species can give quite severe stings causing inflammation, swelling and pain lasting up to a week. Effects may sometimes be more severe.

Divers are particularly prone to brushing against hydroids. Two species to avoid are this white, fine feathery one and the denser yellow/brown type. They can be found in fairly shallow reef areas and on structures such as wharfs.

BOXES OF DEATH - BOX JELLYFISH

Recognized as one of the greatest marine hazards, box jellyfish (Chironex fleckeri) kill more people than sharks, crocodiles and stonefish combined.

Each year, in late summer, the adult box jellyfish spawn at river mouths before dying. The fertilised eggs become tiny polyps which attach themselves to rocks in estuaries. In spring these polyps develop into little swimming jellyfish which migrate down rivers, especially with rains, to feed on shrimp. Unfortunately, they frequent beaches which humans also find attractive. The animal does not actively hunt, relying on food to bump into its tentacles. A struggling shrimp might tear a delicate jellyfish, so it needs to be killed instantly, on contact, with a very strong poison.

Tentacles, up to 60 in number and reaching 5m in length, are arranged in four groups at the corners of a box-shaped bell which can be as large as a basketball. The tentacles are armed with up to 5 000 million stinging cells known as nematocysts. These are triggered into action when stimulated by certain chemicals found on the surface of fish, shellfish and humans. Contact with just 3m of tentacles can kill an adult.

Recent studies have shown that the box jellyfish is able to see through four eyes, one at the centre of each side of the bell. How it processes this information without a brain is still a mystery but the animal is able to avoid even quite small objects. They probably try to avoid humans in the water, if given the chance; stings usually occur when people blunder into them. (They are almost invisible in the water.) It is certainly in the interest of the jellyfish to avoid turtles which eat them, apparently unaffected by the stings.

Another box jellyfish, Chiropsalmus quadrigatus, is generally less common than Chironex fleckeri, although it may outnumber them on Cairns to Port Douglas beaches. It is smaller, with slimmer tentacles, but the two are difficult to tell apart. There are about 20 species, worldwide, in the Cubozoa, or box jellyfish, family, Chironex fleckeri is the most lethal member.

IRUKANDJIS

Although it is more numerous in summer months, the irukandji (Corukia barnesi) can be found all year round and inhabits all waters. A member of the box family, it has one tentacle at each corner of its bell. It is tiny - only 2cm across the bell - but nonetheless packs a massive punch. Both bell and tentacles have stinging cells.

The actual sting is minor, but 20-30 minutes later the victim begins to experience agony which lasts for hours. Although not blamed for deaths its tendency to cause raised blood pressure can be dangerous for vulnerable victims. Ignoring the initial sting may also lead to some people suffering severe symptoms in deep water or while driving.

SEA URCHINS

It is just common sense to avoid the sharp black spines of the black sea urchin. They can penetrate deeply into the flesh and break off causing long-lasting inflammation if not removed – often surgically. There is doubt as to whether venom is also involved.

A less common but much more dangerous urchin is the flower urchin. Instead of long spines it appears to be covered with numerous flowers which are in fact little venomous pincers (pedicillariae) capable of causing paralysis and even death. It has killed several people in Japan.

This derives from dinoflagellates contaminating shellfish (clams, scallops, oysters, etc.). The toxin, saxotoxin, is water soluble, heat and base stabile, and is therefore not affected by steaming or cooking. It inhibits sodium channels of excitable membranes, blocking propagation of nerve and muscle action potentials.

Symptoms: These usually occur within 30 minutes, and include parasthesias of the lips, tongue, gums and face. This process proceeds to the trunk and may progress to paralysis and respiratory arrest. The gastrointestinal form may appear hours or days after ingestion with nausea, vomiting, diarrhea and abdominal pain.

Treatment: No specific treatment. Stop eating if oral sensations are perceived. Empty stomach if systemic symptoms are noted, using emetic or lavage. Give respiratory support and monitoring if needed.