- Objectives: To examine the effect of fluid resuscitation on the hemodynamic changes in dogs injected with scorpion venom and to explore the effects of the venom on the determinants of venous return (i.e., circulatory compliance, time constant, and resistance to venous return). Design: A prospective, controlled animal study. Setting: University animal research laboratory. Subjects: Mixed-breed dogs. Interventions: The effect of volume resuscitation (20 mUkg of the synthetic colloid polygeline) 1 hr after venom injection (a time previously found to be related to severe decrease in cardiac output) was tested in two series of experiments. In the first series, 12 dogs were given venom and fluid, eight dogs were given venom alone, and four dogs served as the time-controlled group. In the second series, eight dogs were given venom and ten dogs served as controls. Scorpion venom (Leiurus quinquestriatus) at 0.1 mg/kg in the first series and 0.05 mg/kg in the second series was given intravenously. Measurements and Main Results: In the first series of experiments, the venom decreased cardiac output from 5.0 ± 1.1 to 2.9 ± 0.7 L/min at 60 mins (p <.001). Arterial pH decreased from 7.39 ± 0.05 to 7.16 ± 0.1 (p <.001). Blood lactate increased from 0.9 ± 0.8 to 3.2 ± 1.9 mM (p <.05). Gastric pH decreased from 7.28 ± 0.2 to 6.7 ± 0.18 (p <.001). Arterial acidosis was secondary to gastrointestinal ischemia because the gradient between mucosal and arterial Pco 2 increased from 17.5 ± 7.7 to 98.6 ± 75 (p <.01) 60 mins after venom injection. In the second series of experiments, circulatory compliance and time constant increased by 150% and 128%, respectively (p <.05), in dogs injected with venom compared with control dogs. Resistance to venous return increased after venom injection but did not change after fluid infusion. In both series of experiments, volume administration improved cardiac output but had no effect on oxygen delivery, arterial pH, HCO 3 -, lactate, and gastric mucosal pH. Conclusions: Metabolic acidosis and cardiovascular abnormalities seen after scorpion venom injection in dogs are closely related to gastrointestinal hypoperfusion. Fluid resuscitation increased cardiac output but had no effect on gastrointestinal perfusion and acidosis induced by the venom.