Puff adder venom shock: a model of increased vascular permeability.

The circulatory, respiratory, metabolic, lethal and tissue permeability effects of an i.v. infusion (30 min; 1.5, 2.0, 2.5 and 3.0 mg/kg) of puff adder (Bitis arietans) venom were studied in Sprague-Dawley rats (n = 35, 275-325 g). Venom (2.5 mg/kg) produced circulatory failure with arterial hypotension, hemodilution, hypoproteinemia, lactacidemia and marked hyperventilation by +4 hr. In a separate test (n = 20, 282-325 g) blood volume was measured at end venom (2.5 mg/kg) infusion (0 time) and at +3 hr with radioiodinated (125I) human serum albumin and 51Cr-labeled rat red blood cells. Venom produced a significant reduction in total blood volume index (9%, P less than .05), plasma volume index (12%, P less than .01) and red cell mass index (6%, P = N.S.) as compared to the control group at 0 time. Critically low levels of these indices were observed (43, 42 and 46%, respectively) at +3 hr. At both intervals the transvascular escape rate of radioiodinated human serum albumin but not 51Cr-labeled rat red blood cells was significantly increased in comparison to the control group. Tissue permeability index to 51Cr-labeled rat red blood cells and radioiodinated human serum albumin was increased primarily in the stomach and small intestine. These data suggest that increased vascular permeability to protein and red cells, primarily in the splanchnic region, leads to hypovolemic shock and death after a lethal dose of i.v. Bitis venom in rats.