Dose and frequency of anti-snake venom injection in treatment of Echis carinatus (saw-scaled viper) bite.

Objectives: To assess the adequacy of initial standard dose of 100 ml of polyvalent anti-snake venom (ASV) and subsequent doses of 50 ml in correcting coagulation dysfunction in cases of viperine bite and to find the incidence of recurrence of coagulation dysfunction. The other objective was to correlate total requirement of ASV with initial coagulation profile.

Methods: Forty two adult patients of Echis carinatus bite with features of systemic envenomation, admitted over a period of 18 months, were monitored every six hours with bed-side clotting time (CT) and were given an initial standard dose of 100 ml of ASV intravenously. Further doses of 50 ml were administered six hourly until coagulation profile normalised or whenever a recurrence of coagulation dysfunction observed.

Results: Twenty one (50%) of 42 patients who received initial standard dose of 100 ml of ASV required a subsequent 50 ml of ASV. Ten (23.8%) of them required a further 50 ml on subsequent test (making the total requirement at least 200 ml). Sixteen (72.7%) of 22 patients who had incoagulable blood at entry required further dose of anti-snake venom (after initial 100 ml), six required 150 ml and ten 200 ml or more before CT returned to normal. Recurrence of venom antigenemia as evidenced by prolonged clotting time was noticed in 15 patients (35.7%). The mean dose requirement of anti-snake venom was 179.2 ml.

Conclusions: Total requirement of anti-snake venom correlated positively with degree of coagulation dysfunction at entry. Hence patients having incoagulable blood at entry should be administered higher initial dose of ASV i.e., 150-200 ml. If needed as judged by CT, subsequent dose of ASV in patients having still incoagulable blood should be 100 ml (and those having mild dysfunction 50 ml) until total correction occurs Recurrence of coagulation dysfunction was observed in approximately one-third of patients and thus, CT should be monitored even after total correction.