necessary. A comparison of the reported fatality rates due to snake bites in Sri Lanka indicates a significant reduction in mortality in the recent past 2,3,4. The easy availability of antivenom serum in Government Hospitals and facilities for intensive care management may have contributed to the reduction in mortality 5,6,7. Furthermore, early hospital admission due to greater awareness of the public of the availability of effective treatment may also have been an important contributory factor in reducing mortality rates.
The efficacy of AVS treatment in snake envenoming is widely accepted 4,5. The AVS available in Sri Lanka are polyvalent equine sera manufactured in Haffkine Laboratories and the serum institute of India. However, adverse reaction to AVS are common. These reactions vary in severity from mild pyrogenic reaction to severe anaphylaxis 6. This has led to a reluctance to use of AVS specially among doctors practicing in peripheral hospitals. There are several reports describing the adverse reactions of AVS but not many address the advantages of AVS. Further, irrational use of AVS also been reported. These include the use of AVS in bites of hump nosed viper, and in bites of cobra, common krait, and Russells viper in the absence of systemic envenoming 7.
Considering the advantages that AVS can offer in the treatment of snake bite envenoming, a concerted effort should be made to encourage rational practice in the treatment of snake bite. The aims of this prospective study were to investigate the effectiveness and document the adverse reactions to AVS administration in hospital practice in Sri Lanka.
This study was conducted in the General Hospital, Anuradhapura. The study commenced in September 1998.All patients admitted to the unit A, of General Hospital, Anuradhapura with a history of snake bite were observed closely. Out
of these, 60 consecutive cases, who were treated with AVS were carefully observed, and examined whenever necessary. Any reaction following treatment with AVS was immediately recorded in a pre designed observation form, categorizing reactions into two groups, minor and major based on certain criteria. Minor criteria were rigor, fever, sweating, itching, urticaria, abdominal pain, cough, rhonchi, and increased body temperature. Major criteria were dyspnoea, cold clammy skin, central cyanosis, tachycardia, low volume pulse, and hypotension. The reactions were grouped as mild, moderate and severe based on the above criteria. Development of cold clammy skin with any combination of reactions were considered a severe reaction, combination of less than six minor criteria was considered mild reaction and combination of minor criteria plus any major criterion other than hypotension and cold clammy skin was considered a moderate reaction. Other data recorded included age gender, previous history of significant medical illness, history of eczema, catarrh, and urticaria and food and drug allergy. The offending snakes were identified either by studying characteristics of the dead snake if it was produced, or by showing specimens of snakes. If both failed, clinical features were used in identifying the type of snake. Accordingly the bites were grouped as Russells viper bites, common krait bites or cobra bites. The time of the initial reaction and the time period of reaction after the administration of AVS was also recorded. However, routine method of management of the snake bites was adopted in the unit. The routine way of the management of snake bites in the unit was to administer a standard dose of 10 vials of AVS when indicated after a snake bite and this dose was doubled in severe cases. With the onset of adverse reaction to AVS, hydrocortisone 400mg and chlopheniramine 10mg by intravenous bolus injections were administered while continuing the AVS infusion. If the reactions were complicated with vomiting, metochlopramide 10mg (IV bolus) were given. In the case of continuing severe reactions, intravenous hydrocortisone 1000mgs was infused over one hour. Severe anaphylactic reactions were managed with subcutaneous adrenaline in addition to the above.