Severity of envenomation Severity of envenomation depends on the following: Size and species of the snake (rattlesnakes > cottonmouths > copperheads) Amount of venom injected per bite (cannot be determined by history) Number of bites Location and depth of the bite (eg, envenomation in bites to the head and trunk tends to be more severe than in bites to the extremities) Age, size, and health of the patient Time elapsed before treatment Patient's susceptibility (response) to the venom Severity of envenomation can be graded as minimal, moderate, or severe based on local findings, systemic symptoms and signs, coagulation parameters, and laboratory results (see table).