African Snakebite Institute – Hospital Treatment of Snakebite
The majority of snakebite victims have no idea what snake they were bitten by often because the bite happened at night and the snake was not seen or simply because identifying snakes is not easy.
This complicates first aid treatment, but as most bites are from snakes with cytotoxic venom there is often little one can do other than getting the victim to the nearest hospital. For more detailed information on first aid for snakebites go to http://bit.ly/snakebiteapp.
People often ask which hospitals stock antivenom. This is not hugely important as any hospital with a trauma unit can easily stabilise a snakebite victim. Nine out of ten snakebite victims do not need nor receive antivenom, and as cytotoxins are relatively slow-acting venoms, there is usually time to either transfer patients or arrange antivenom, if the hospital does not have any.
Most snakebite fatalities in southern Africa result from Black Mamba or Cape Cobra bites and the reason is that these snakes have quick-acting neurotoxic venom that causes progressive weakness and compromises breathing. If such victims are quickly hospitalised, they can be intubated and ventilated.
Always take a snakebite victim to the nearest hospital with a trauma unit. Such hospitals are geared for medical emergencies and in high-risk snakebite areas, they usually stock antivenom.
Once hospitalised, a snakebite victim will be carefully monitored for at least 12 hours (although it is preferable to keep such patients in hospital for at least 24 hours). The patient will have two intravenous drips and, if the hospital has the facilities, blood will be drawn and analysed.
About four out of ten patients that are hospitalised develop no symptoms and are discharged without treatment. Most of those that do develop symptoms develop swelling and pain. While such swelling might be extensive and result in severe pain, it is mostly localised and typical of bites from snakes like the Rhombic Night Adder and Bibron’s Stiletto Snake. As there is no antivenom for bites from these snakes, patients are treated for pain and rehydrated. The affected limb is elevated, and patients should rest until the swelling subsides. This could take up to a week or two.
Boomslang bites and bites from the Vine or Twig Snake are rare and usually happens when someone tries to grab one of these snakes or accidentally stands on one which is basking. As these snakes are tree- and shrub-living and are generally extremely placid, they pose little danger to humans. In a suspected bite from one of these snakes, the victim needs to be hospitalised for at least 30 hours and the required blood tests need to be done every few hours. The venom from these snakes is haemotoxic and compromises the blood clotting mechanism, resulting in blood oozing from the fang punctures, then the nose, mucous membranes and elsewhere, followed by severe headaches. As there is no antivenom for the bite of the Vine Snake, there is little that doctors can do for victims and supplementing blood platelets and blood transfusions will not necessarily be lifesaving. To date we have not had any fatal bites from the Vine Snake in South Africa but there have been deaths elsewhere in Africa.
In rural settings where a hospital does not have facilities to analyse blood samples, doctors can do a 20-minute whole blood clotting time test. Blood is drawn and placed in a glass vial which is left on a shelf for twenty minutes. It is then turned upside down and if normal, the blood will clot but if not, it remains liquid. Such tests can be conducted every two or three hours.
In cases where victims are bitten by snakes with predominantly neurotoxic venom, the onset of symptoms is quicker. Soon after a bite victims may report a sensation of pins and needles in the lips followed by difficulty in swallowing, excessive sweating, nausea and vomiting, drooping eyelids (ptosis), and dilated pupils and eventually difficulty with breathing. In such bites, there is little pain and minimal swelling. For neurotoxic bites, doctors look for progressive weakness and a clear sign would be a drop in oxygen levels in the blood.
In cytotoxic bites, doctors look for progressive swelling and this may happen in serious bites from the Puff Adder, any of the spitting snakes and even some of the cobras. Should the swelling spread up a limb at a rate of 10 – 15 cm per hour, it will be a good indication that antivenom should be administered.
For the venom of the Boomslang, we have a monovalent Boomslang antivenom, manufactured by the South African Vaccine Producers in Johannesburg. It costs R 6 800.00 per vial and most patients initially receive two vials. This is administered intravenously via a saline drip and over a period of about 30 minutes. Prior to such administration, doctors give the patient a small dose of epinephrine (adrenalin) to prepare the body for any allergic reaction that may follow. Once the antivenom has been administered, doctors will monitor the progress of the patient carefully and, if necessary, administer another vial or two if there is no marked improvement.
In Boomslang bites, antivenom should be given the moment there is evidence that the blood clotting mechanism has been compromised.
For cytotoxic envenomation, doctors will administer between 6 and 12 vials (60 – 120 ml) of polyvalent antivenom via a saline drip and over a period of about 30 minutes. Less than 6 vials are rarely beneficial. Polyvalent antivenom is produced by the South African Vaccine Producers in Johannesburg and is made from the venom of ten snake species. These include our cobras, mambas, Rinkhals, Puff Adder and Gaboon Adder and cost close to R 2 000.00 per vial (10ml).
Up to 40% of patients that are given antivenom in South Africa have a mild allergic reaction. This might present in the form of some hives, itching, nausea, skin rash or goosebumps but in severe cases the patient may experience anaphylaxis. Anaphylaxis is a life-threatening allergic reaction with patients experiencing low blood pressure (hypertension), constriction of the airways, swollen tongue and throat, wheezing, a weak and rapid pulse, dizziness, or fainting. The treatment for anaphylaxis, as mentioned, is adrenalin. It stimulates the adrenoceptors which increase peripheral vascular resistance, improving blood pressure and coronary perfusion, which decreases swelling. For these reasons antivenom is only administered in a hospital environment and is not a first aid solution.
Antivenom does not reverse damage already done and the sooner a patient receives antivenom (if required) the better. In bites from snakes like the Mozambique Spitting Cobra and Puff Adder, especially bites on fingers and hands, the venom may do severe damage to tissue, and such bites may require surgery and skin grafts.
For severe neurotoxic envenomation, doctors administer 10 – 12 vials (100 – 120 ml) of polyvalent antivenom via a saline drip over a period of about 30 minutes. Should the patient not show signs of improvement soon after receiving the antivenom, further vials of antivenom will be given. It is not unheard of for Cape Cobra or Black Mamba bite victims to receive 20 vials of polyvalent antivenom.
Despite the dangers of a severe allergic reaction to antivenom, such complications are manageable and antivenom is the correct and only treatment for severe snakebite envenomation.
Some snakebite victims experience serum sickness 5 – 14 days after being treated with antivenom. It is basically an immune reaction to foreign proteins when the body mistakes such proteins as being harmful. It is not a serious medical condition and patients may experience rashes, itching, joint pain, swelling and tenderness of the lymph nodes, hypotension, and fever. Serum sickness is treated with corticosteroids, antihistamines, and analgesics.
Most snake bites are easily and successfully treated in hospitals and very few people die from snakebite in southern Africa. Most of the deaths from snakebite we see in southern Africa are in rural areas or are as a result of people seeking herbal remedies and alternative medicinal practices. If the victim is taken to a hospital as soon as possible, the chances of survival and recovery are almost 100%.
By Johan Marais of the African Snakebite Institute