Snakebite envenoming in Kerala, South India: clinical profile and factors involved in adverse outcomes.

Background: Snakebite envenoming is an important medical emergency in Kerala, but the factors leading to complications have not been well studied.

Objectives: To study the clinical characteristics, factors involved in complications and the outcomes in relation to timing of polyvalent snake antivenom (SAV) administration in patients with snakebite envenoming.

Methods: Patients were recruited from cases of snakebites admitted to the emergency care unit of Kottayam Medical College between May 2005 and December 2006. The manifestations of envenoming and complications were recorded. SAV was administered to cases with envenoming. Treated patients were analysed to determine the factors involved in complications and the outcomes in relation to the timing of SAV.

Results: 200 (34%) of 586 cases with snakebites had envenoming; 58% were men, 52% were aged 31-50 years and 93% were outdoor bites. The species of snake was identified in 34.5% of the venomous bites. 93.5% had signs of local envenoming. Regional lymphadenitis occurred in 61%. The mortality rate was 3%. Capillary leak syndrome, respiratory paralysis and intracerebral bleeding were the risk factors for mortality. Those who received SAV early (bite to needle time <6 h) had more severe local envenoming than those who received SAV late (bite to needle time >or =6 h), but the latter group were more likely to suffer complications. 39.5% had complications, with acute renal failure being the most common (25.5%). Those who received SAV late had a higher risk of developing acute renal failure. Higher rates of complications were seen in those with severe coagulopathy (OR = 8.0), leucocytosis (OR = 3.7) and those who received SAV late.

Conclusions: Early administration of SAV reduces the risk of complications. The presence of leucocytosis and severe coagulopathy can predict adverse outcomes.