Health
Fangs
Now is the time to unlearn everything you’ve ever heard about snakebite.
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The reason for all this misery is that, internally, part of the body is being digested. The physiology of snakebite bears little resemblance to the prevailing concept in which dollops of amber toxin ooze slowly through the veins towards the heart. Instead, when a venomous snake strikes a human, within moments of the bite an inexorable metabolic disintegration of the body’s living tissue begins. An elaborate mixture of toxic proteins, venom is only partially targeted toward killing prey; its primary function is digestion, which enables the snake to eat animals plumper than itself by starting the digestive breakdown even before it swallows the prey. What this means for human victims is that even in the hospital it is almost impossible to get the poison out. For all practical purposes, venom simply becomes part of the body, and trying to extract it is generally as hopeless as trying to retrieve ink dripped on a wet sponge.
Experiments with animals have shown that even excising the entire bite area has not extracted enough venom to save the lives of individuals that received a lethal dose. Therefore, making mere drainage incisions, whether small ones through the fang marks or bigger ones that open the entire limb, is a largely futile gesture. Only rarely can even an accomplished surgeon remove a pocket of venom deposited deep within the muscle; it’s obviously nothing to try on your own.
Moreover, any self-administered incision is risky because the anticoagulant effect of pit viper venom makes it hard to stop the bleeding. Knife cuts into a bitten limb—especially incisions big and deep enough to drain the venom-saturated tissues—invariably result in a far greater loss of blood than you would expect, a loss that is particularly dangerous after sever venom poisonings because when people die of snakebite, they die of loss of circulating blood volume. Because it’s so generalized, this subtle internal bleeding often goes unnoticed. It occurs when peptides and enzymes in the venom pierce the capillary walls, allowing a fine seepage of plasma into the tissue spaces, This blood pools both in the lungs and subcutaneously in the affected limb, where it appears as swelling. Here, even a minimal amount of swelling—a two- or three- centimeter increase in the circumference of a thigh, for example—can indicate a loss into the tissue spaces of as much as a third of the body’s plasma, bringing about radical fall in blood pressure and putting the patient into potentially lethal shock.
Given the drawbacks of incision, then, what of the other traditional first aid approach—trying to localize the venom by binding or chilling? Again, except in desperate situations, most authorities feel it’s better not to try to impede the body’s essential circulatory exchange, because such attempts have so frequently had disastrous results. The worst of the containment therapies was ligature cryotherapy, or L/C, treatment, which first gained popular attention during the early fifties. Touted as a revolutionary way to avoid the perils of incision and suction, it combined instead two of the most destructive things people have ever done to their limbs: putting tourniquets around them (ligature), then chilling the constricted part in ice (cryotherapy). As might be expected, venom-saturated tissue subjected to the cell-membrane-cracking effect of massive chilling and deprived of normal blood and lymphatic flow frequently died. It died so frequently, in fact, that amputations following ligature cryotherapy became almost routine and the procedure has for the most part now been abandoned. The original assumption was that extreme cold would slow down the action of the venom, but the currently prevailing view is that nothing short of totally freezing—and thus killing—a limb can substantially deactivate reptilian poison. There is even evidence that cold may drive the venom deeper into the muscles.
Much of the emphasis on such radical first aid originated during the thirties, when doctors often didn’t see patients until two or three days after a bad bite. That’s simply not the case anymore. Because most people now reach hospitals so quickly—the longest gap between bite and treatment recorded in the state recently is five and a half hours—the horrors of long-chilled, frostbitten limbs that used to shock emergency room personnel are seldom encountered today. But a dangerous legacy of the ligature-cryotherapy school remains in the widespread use of tourniquets. Any band cinched tightly enough to cut off blood flow for more than forty minutes is likely to cause permanent injury, whether or not the damage is apparent at the time. This is such a hazardous procedure, in fact, that wrapping tight bands around a bitten limb (except in the desperate case of a toddler bitten deeply by a big rattler) is now decried by everyone involved in treating snakebite.
The ultimate means of trying to contain the venom is a surgical technique called debridement, involving the removal of the toxin-infiltrated tissues. But this operation, which usually includes stripping irreplaceable nerve sheaths and tendons, calls for such fine judgments that the majority of physicians choose instead to open the entire limb surgically in hopes that relieving the pressure by enforced drainage will make tissue removal unnecessary. They are operating, however, on the false belief that excessive swelling in the limb can cause high enough internal pressure to choke off circulation. In treating more than seven hundred snakebites, however, including many by extremely virulent exotic species, Dr. Findlay E. Russell, of the Department of Pharmacology and Toxicology at the University of Arizona, has never encountered a single case that justified this radical procedure. He has found instead that even enormous swelling is soft, involving only the shallow subcutaneous layers, and that the tissue death (except that resulting from ill-advised first aid) is the direct result of the disintegration of the body’s cells by the venom. Only a handful of experienced surgeons are capable of determining how much of the darkened tissue around the bite should be excised, and because surgical solutions have so often involved permanent impairment of the limb, the prevailing treatment for snakebite in most of the country is antivenin.
Antivenin is a crystallized assemblage of antibodies made by Wyeth Laboratories from the blood of horses injected with minimal doses of snake venom. Antivenin counters both neurological damage and local tissue death in a straightforward way: it clogs up the venom proteins until they are no longer able to attack their target cells. Like any other immunization, antivenin therapy depends on building up a sufficiently high protective level of antibodies in the bloodstream to neutralize the dispersing toxin. But because this level must be attained so quickly, the patient may experience rapid and severe allergic reactions, which can be fatal within minutes without the shock drugs and respiratory assistance of a good intensive-care facility.
Russell has met with such success in controlling these adverse reactions with antihistamines, however, that he now routinely administers antivenin, even to a patient whose preliminary skin test indicates potential hypersensitivity. Proponents of this view maintain that not only does antivenin offset the major, life-threatening systemic failures that may follow a severe snakebite but it is also the only significant method of protecting the tissue near the bite of disintegration. Nevertheless, surgery is still the primary method employed at most hospitals in Texas, although neither treatment is warranted in the majority of bites. In the last eight years Houston’s Ben Taub Hospital has administered no antivenin at all and performed only on fasciotomy, even though each year it treats an average of 25 snakebite cases.
Either treatment will almost certainly pull you through—a fraction of one per cent mortality is a good shot on anybody’s table—although pulling through is still a long way from being all right. People vary enormously in how sick they get from snakebite poisoning and how long they stay that way, but it’s generally a lot longer than you’d expect, especially with rattlesnake venom. It’s not unusual to feel absolutely rotten for weeks, even from minor poisonings where no threat to life or even limb ever existed. Long after the emergency stage has passed, muscles and organs are still having to cope with metabolic wastes left in the wake of the poisons, and violet and yellow bruiselike discolorations may show up anywhere on the body for days. Even with the best treatments, some tissue death almost always occurs in the area of the bite, and enough skin may slough off to require grafting. Because both coral snakes and pit vipers carry substantial amounts of neurotoxins, their bites can impair coordination in the limb itself for weeks, as well as affect the neck, jaw, and eyes.
In addition, the aftereffects of the treatment itself cause discomfort. Each approach has its problems. Fasciotomies left open to drain for days take a lot of healing and, like any major incision in a limb, necessarily run the risk of some permanent loss of flexibility due to scarring, though good surgical technique can keep that to a minimum. Antivenin therapy can also produce residual problems. A week to ten days afterward, as the last particles of venom precipitate out of the bloodstream, rashes, aches, and fever similar to a mild case of flu are typical, sometimes followed by heightened sensitivity to inoculation with any horse-based serum.
Being struck by a venomous snake—as bad as the worst cases are—is nevertheless one of the most interesting misfortunes, automatically conferring on the victim a degree of lifelong celebrity. Especially with the less toxic copperhead poisonings and with superficial rattler bites, the notoriety may even make getting bitten less of an ordeal. Bill’s hospital room was so full of intrigued visitors that for the first couple of days Elaine and I took turns running interference in the hallway, and when he was released, half the people we knew vied for the honor of giving him a snakebite recovery party.
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