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Medical Zambia

Cobra

Male Kudu

Just before dawn at 5:30am, he was emptying the ashes from last night’s campfire into the pit latrine when he felt a sharp pain in his foot. He looked down to see a small snake rearing up ready to strike a second time. When he saw the hooded neck, he knew it was a cobra. He retreated quickly and the snake slithered off into the bush. There was no thought of revenge, no need to kill the snake for identification purposes. There were two small puncture wounds on the outer border of his little toe.

I didn’t get word of this until 7:30am when I was en route to Mambwe to see the District Medical Officer. My appointment was for 8am and it had already been cancelled once so I opted not to turn around. The nurse in charge at Kakumbi is very senior and no doubt had managed many snake bites in the past. I alerted him by SMS that the patient would be arriving by boat from a bushcamp at about 8:45am.

I instructed the camp manager to get some polyvalent (it counteracts envenomation from the most common snakes in the region) antivenin from the medical refrigerator in my house and bring it to the clinic in a cold bag.

The important thing to do in these situations is for both the patient and health care worker not to panic. Gone are the days of slicing into the fang marks and sucking out the poison; the patient is likely to get a nasty infection and it has no effect of the outcome. Tourniquets are only useful if you know that the venom is neurotoxic, to stop the spread of the poison around the body before the doctor can administer antivenin. Wash the wound to remove any venom on the surface, then keep calm and rest is the official advice.

At Mambwe District Health Office I met our former pharmacist from Kakumbi. “Does Kamoto Hospital have any antivenin?” I asked him. He said no, while remarking that they had had more snake bites than usual this rainy season.

I received a text that the patient had arrived and discussed the management plan with the nurse in charge. He set up an intravenous infusion which we would need if we were to give antivenin, gave the patient some diclofenac anti-inflammatory pain killer, a tetanus toxoid booster and insisted on complete bed rest. The initial observations were encouraging and I felt I didn’t need to rush back to the clinic.

About half of snake bites are “dry” and don’t contain significant amounts of venom. The snake is just protecting itself; it is not planning to eat the person it has bitten. In my patient’s favour were the following factors – he was a 70kg man and the snake was small, less than a metre in length; the bite was on the foot, rather than the head or neck; he received prompt first aid.

I have written about snakebites in Swaziland in my blog in the past if you want to learn more, click here. In simple terms, venom from vipers causes local pain, swelling and necrosis around the bite and venom from cobras is a nerve toxin which causes paralysis. We were closely observing the patient on the lookout for signs of paralysis which can begin upto five hours after the bite.

The decision to start antivenin is tricky. Ideally, the best results are when antivenin is administered soon after the bite, but it may not be needed and there is a high likelihood of the patient developing anaphylactic shock and dying. Some experts give adrenaline before the antivenin. We didn’t have any adrenaline at the clinic. The antivenin that the camp boss brought to the clinic was past its expiry date, so I told the nurse in charge that it would be my decision whether we used it or not, not his. He gave some hydrocortisone instead.

“Are you looking at me?”

As an aside, what would you rather have if your life was at risk from envenomation – antivenin which was out of date (and possibly less potent as a result) or no antivenin at all? I’d go for the expired stuff, personally, evn though my safari supply of adrenaline was also out of date.

When I got back to the clinic, I reviewed him. His blood pressure and pulse were stable, his pain was controlled and the bite site was not swollen. He was hungry and had eaten a late breakfast (patients with significant neurological damage cannot swallow or open their mouths). His breathing was relaxed and not laboured. An early sign is drooping eyelids, but his eyes were normal. This leads on to respiratory arrest and I would have had to intubate and hand ventilate the patient until we could get him to an intensive care unit, probably at Chipata Hospital a few hours away.

Ground Hornbill – in a tree. He kills cobras.

When I left the clinic at 1pm, there was no change in his condition and he had passed the critical five hour period where “cobra syndrome” can occur. I felt he should remain on the ward for at least 12 hours, possibly staying overnight, just to be on the safe side.

I was surprised when I opened the cold box containing the antivenin when I returned home. The camp boss had just brought one vial. Sometimes it can take ten vials to control mamba or cobra envenomation. I discovered that the fridge sorely needed defrosting and now I know exactly where to find adrenaline for injection. Even if it is expired.

Lady Luck smiled on us today.