Surviving the Extremes: A Doctor's Journey to the Limits of Human Endurance (8 page)

The snake remained motionless. For hours, Antonio lay on his back watching the bulge covered by his T-shirt, afraid to either move
or yell for help—afraid to see the T-shirt start to tent up from below. Just after sunrise, the tent and the snake began to heat up. Soon the snake became uncomfortable and started moving around. At last Antonio felt it slide slowly past his thigh, down his other leg, and out over his foot. He waited a few more seconds before he dared to get up, and when he did, the snake was gone. He never saw it.

Later I asked Antonio what kind of snake he thought it was. He believes it was a small Cascabel—a deadly poisonous pit viper. He said it was about 3 feet long and very heavy. Its scales felt rough against his skin, and it was black and gray. I asked him how he knew it was black and gray if he never saw it.

“I see it in my dreams,” he replied.

I wondered if he was thinking about that when he told me that snake heads cast bad spells. For me, and for most people, simply looking at a snake is enough to elicit a mixture of chills, fear, and revulsion—a dramatic, but not altogether inappropriate, survival response, considering that poisonous snakes kill over one hundred thousand people per year, roughly half of them in India. No wonder some Indian religions worship snakes as gods to be feared.

Poisonous snakes are highly evolved killing machines. Their venom is a special saliva formed in glands behind their jaws. During the bite, the glands contract, squeezing the venom forward into the fangs, which are hollow teeth with holes at the pointy ends. The system is very much like an injection with a hypodermic needle.

Venom is a complex potion, not easy for a snake to produce. Therefore the snake has to use it sparingly, and only for very good reason. While the snake will always inject venom into prey, when biting defensively it may or may not envenomate its assumed attacker. It first quickly assesses the risk in order to decide whether using up venom is necessary. When humans are envenomated, it is almost always because the snake felt mortally threatened, from being stepped on or poked at. Snakes do not want to waste their venom on humans, which are not prey. Because a snake’s teeth point backward, they are good only for gripping; snakes can’t tear apart or chew their prey, and humans are too big to swallow whole.

Venom is a mixture of poisons and of enzymes, substances that
dissolve body tissues. Each kind of snake makes its own variety; the effect of venom inside the body therefore depends on its individual recipe. The coral snake I met near the latrine uses mostly nerve poison, while the snake that slept with Antonio prefers to poison the blood. Both types are quick and deadly because they attack the body at its weakest points—the fragile chemical reactions critical to the dynamics of breathing, heartbeat, and blood clotting.

Muscle contractions make hearts beat and lungs breathe. Muscles are powerful machines that can sustain a lot of damage and keep on going. But like a lot of machines, they will stop cold when unplugged. They depend on the constant supply of electricity that reaches them through the wiring system of the nerves. Small spaces exist between each consecutive nerve and between the nerve and the muscle. When the current comes to the end of a nerve, it faces a gap it has to jump if it is to continue. The nerve end releases a chemical called a neurotransmitter that floats across the gap and sparks the next nerve. The last nerve before the muscle ends in a group of tendrils, like a multipronged plug, that align with but don’t quite connect to a corresponding socket in the muscle. Another neurotransmitter has to float a connection between the two. It is precisely this last delicate step that the coral snake’s venom blocks. The venom mimics the neurotransmitter and fills the gap, but it does not conduct the signal. The transmission of electrical impulses is interrupted; muscles fire irregularly, then weaken, and finally become paralyzed. The victim twitches, collapses, and loses the ability to speak. Within a few hours the paralysis overtakes the pulmonary and cardiac muscles. The lungs stop breathing and the heart stops beating.

The pit viper uses a different but equally lethal technique. Its poison weakens the walls of blood vessels, allowing blood cells and fluid to leak into the surrounding tissues. Whenever a blood vessel is breached, the body’s natural defense is to set off a cascade of reactions that convert free-floating raw materials into a sticky mesh that forms a clot to seal the hole. That process, known as coagulation, is why a cut stops bleeding. Pit viper venom sabotages the intricate sealing process with an ingredient that mimics one of the crucial raw materials and gets itself incorporated at an early step. It is much weaker than
the real thing, so the final clot ultimately gives way. The mesh cannot form a seal strong enough to stop the bleeding. It is a fatal weakness: the blood goes everywhere but where it belongs, filling the lungs and emptying the heart.

Because venoms are thick, they contain an additive, hyaluronidase, that helps diffuse their poisons. Doctors routinely add this dissolving enzyme to injected medicines to increase the rate of absorption. Snakes use it to speed up the spread of their venom. Snakes also inject another enzyme that digests muscle. It causes the severe tissue destruction often seen at the site of a bite, but its real purpose is to give the snake, which cannot chew, a head start on its anticipated meal.

Treating someone who has been on a snake’s menu is not easy. If he has been envenomated, he will probably die. Venom is not a single poison; one injection is similar to a multidrug overdose. The catastrophic breakdown of many organ systems that rapidly follows the poisoning is hard to reverse, even in the most sophisticated hospital. In the jungle it would be impossible. But less than half of all bites from poisonous snakes actually inject venom. Fang marks are sometimes hard to see, particularly because they are often obscured by swelling. Tingling, facial numbness, palpitations, and difficulty breathing can be early indicators of envenomation, but given the near hysteria aroused by snakebites, those signs can be present in anyone.

If I were treating a snakebite, my first job would be to calm the patient down—not just for the psychological benefit but to slow the spread of the venom. At Zancudo Cocha I had an extractor, a plunger type device that if applied to the bite wound within the first few minutes might draw out some of the venom. It might also be a waste of time. No one knows for sure how effective it is. I would not try sucking the venom out by mouth, though not because I would be afraid of swallowing poison. As potent as they are, these poisons are easily broken up by stomach enzymes. Snake venom only works when it enters the bloodstream directly. Anyway, venom is so thick that sucking it out by mouth would not work. Even worse would be making a cut over the bite and trying to squeeze the venom out. That would expose more blood vessels to the venom and probably drive it
in deeper under pressure. I could slow the poison by applying a wide bandage over the whole limb. With just enough pressure, I might be able to block the veins from carrying contaminated blood to the heart while still allowing inflow from the deeper arteries, which would carry fresh blood into the limb to keep it alive.

I didn’t bring any antivenin on this expedition but not because I forgot. The most effective antivenins are specific for each species of snake, and there are over one hundred varieties of poisonous snake in the Upper Amazon Basin. General antivenins are not as effective. Many bottles are required, the injections themselves are dangerous to give outside a hospital, and worst of all, they have to be kept refrigerated. Antivenins are antibodies, natural body chemicals that patrol the bloodstream and deactivate antigens—foreign chemicals, such as snake venom, that find their way inside the body and cause havoc. Each antibody is specific to one kind of antigen and only manufactured in quantity once the body has been exposed to it. When enough is manufactured, it can counteract the antigen and stop the problem. This is how we “get over” a cold. But snake venom, like many deadly diseases, doesn’t allow enough time for the antibody response. The solution is to have the antibodies ready to go—premade by injecting sublethal doses of venom into animals and then collecting the antibodies they develop. This is how vaccines work. But antivenins have a lot of impurities and can create their own deadly side effects. After consulting with experts at the Bronx Zoo, I decided they would be too impractical for this expedition. People on expeditions understand they assume risks when they enter an extreme environment. Practical decisions I make may have fatal consequences. The responsibility would be mine.

There would be nothing more I could do if a snake sunk its fangs into a member of my team. Evacuation was impossible. We were surrounded by thousands of miles of trees and plants . . . but maybe one of them held a cure for snakebites. I asked Antonio what he would have to offer if one of us were bitten. He said he once treated somebody who had been bitten by a bushmaster—probably the deadliest snake in the Amazon. He made a poultice from the inside of a tree
bark, added a few plants, then boiled it until it had turned into a syrup. He gave the victim one dose every day. The plan was to give a total of five doses, but on the third day the patient died.

“Yeah,” I mused. “I don’t know why that happens. Sometimes you follow the treatment protocol exactly, and the patient still doesn’t get better.”

The laws of nature are sometimes simply overwhelming, and doctors are powerless to intervene. Bodies have limits. Though the people who live in the Amazon have adapted to their surroundings, they have done so mostly on brainpower. As evolving organisms, they are still works in progress, having not yet acquired adequate physical protection against their most extreme hazards. They remain as vulnerable to snakebites in their environment as we are to automobile accidents in ours. Where one mistake can often prove fatal, survival results not from experience but from being taught, whether the lesson is how to spot a snake or how to cross a street.

Out of the forest one day appeared an Indian who had traveled three days with his family to see me. He had a severe limp, and it had obviously been a difficult trip. He told me that his leg had gotten weak after a childhood sickness, then stopped growing. His left leg was badly atrophied and several inches shorter than his right. The foot was angled down and rigid, touching the ground only at the toes. He hadn’t been this far from his village for years, but he had come because he had heard about my surgery on Berullio’s son’s arm and thought that perhaps I could help him as well.

With one look I knew that I could not. His childhood disease was probably polio, and his deformity, after all these years, was permanent. The best treatment would be amputation, followed by crutches and a prosthesis, but that would be absurd here. He would have to leave the Amazon. With a wife and three small children, he had obviously adapted well to his condition and had no intention of going anywhere else. There was nothing I could do for him.

Well, almost nothing. He said his entire family was with him and asked if I would take a picture of them. A family photo. I was happy to oblige. Father and mother in back, the three children in front, all of them taking a serious Victorian pose—I used a Polaroid camera and
handed them the snapshot as it came out. Without my telling him, the father knew to hold it at the edges until it was fully developed. I got the distinct feeling that this was not the first Polaroid photo he had, nor was I the first doctor he had seen.

My medical practice was steady, but not every problem was serious. Though all the biologists wore boots, and most of the Indians did not, we were the ones who developed foot problems. To the endless amusement of the native crew, I treated blisters and foot fungus caused by boots that couldn’t be kept dry on the inside. They teased us by pointing to their bare feet, thickly callused from a lifetime of walking in the jungle. Tenderfoots like us always considered calluses a nuisance, but here they were nothing less than an adaptation for survival.

One member of our team made the mistake of lighting a fire under a small tree while out in the field. It smoked out some stinging caterpillars, which dropped from a low branch. One fell harmlessly in her drinking cup but a few others landed on her arm and neck. The stings themselves weren’t so bad, but now she was getting itchy. Native to the Upper Amazon Basin are iridescent caterpillars with venomous spines that can deliver fatal stab wounds, but the ones that attacked this biologist were the multicolored kind and only caused a simple irritation from the sticky hairs still adhering to her skin. The treatment was a strip of duct tape that I applied as if I were removing lint from a jacket.

For one complaint I found it hard at first to maintain a serious medical demeanor. An expedition member came to me, pointing to his buttocks. “There’s something moving around back there,” he told me, unnerved and embarrassed. He pulled his pants down and bent over, and I undertook a flashlight search. Each buttock featured several white pimples with black plugs in the centers. And each of the black plugs was wiggling. It was an infestation of tungas, small black fleas that hang out on the ground in areas of cleared brush such as that around our latrine. When offered a target as tempting as bare buttocks resting just above the ground for several minutes, they literally jump at the chance, tunneling into the skin headfirst until only their tails are left protruding. This convenient arrangement allows them to suck blood and defecate without changing position. They grow to pea size,
and when ready to lay eggs, they wriggle around, causing intense itching. The scratching that follows helps release and disperse the eggs. One of nature’s more lowly animals, the tunga has nevertheless developed a very clever survival strategy.

I applied a cotton ball soaked in alcohol to each protruding flea tail and left it in place for several minutes until I was sure the flea was dead. Then, with a scalpel, I made a slit across the hole at the center of each pimple and folded back the skin on either side to expose the body containing the egg sac. Using tweezers, I pulled it out carefully; rupturing the egg sac could lead to a severe infection. Once the body was removed, the head became visible, embedded in the tissues firmly enough to have snapped off when I pulled on the body. With no fragile egg sac to worry about, I could pull much harder to extract the stubborn head.