Retrospective evaluation of neurotoxic rattlesnake envenomation in dogs and cats: 34 cases (2005–2010)

Abstract

To describe common physical examination findings, clinicopathologic changes, treatment, and outcome in patients with evidence of neurotoxicity secondary to rattlesnake envenomation. Retrospective multicenter study (2005-2010). Three private veterinary referral centers. Thirty-four client-owned cats and dogs with evidence of neurotoxicity secondary to rattlesnake envenomation. None. Patient signalment, approximate time between envenomation and presentation for veterinary evaluation, physical examination and clinicopathologic findings, treatments, serial neurologic assessment, duration of hospitalization, and outcome were recorded. Signs of neurotoxicity such as ataxia, postural deficits, muscle fasciculations, paresis, paralysis, or seizures were required for inclusion into the study. The incidence of neurotoxicity amongst the general population treated with antivenin for rattlesnake envenomation in this study was 5.4%. Crotalidae Polyvalent Immune Fab(b) and veterinary approved Antivenin (Crotalidae) Polyvalent(a) were both used in this study. There was no statistically significant difference between type of antivenin or number of vials of antivenin administered and neurologic status, length of hospitalization (LOH), or survival. Hypokalemia was a frequently identified complication, but the presence of hypokalemia did not have a statistically significant association with LOH or survival. Four of the 34 patients (11.8%) required positive pressure ventilation for signs consistent with respiratory paralysis; 2 of these patients survived to discharge. Overall mortality rate was 17.6%. Survival was not significantly different between dogs and cats. However, cats had a significantly longer LOH when compared with dogs (median LOH 3.5 d for cats, 2 d for dogs). Cats appear to be overrepresented in the subset of envenomated patients with neurotoxicity. Although the incidence of neurotoxicity secondary to rattlesnake envenomation may be relatively low, patients can have rapid progression of their clinical signs and a higher mortality rate, necessitating timely and appropriate treatment. Patients treated for neurotoxicity secondary to envenomation appear to have a fair to good prognosis.