Effect of ligation of spleen vessels on left ventricular function and coronary blood flow in dogs injected with scorpion venom.

Scorpion sting may cause myocardial dysfunction in human victims, probably by increased O2 demand and decreased O2 supply. In dog, scorpion venom (SV) causes no myocardial dysfunction. Myocardium is probably protected by "autotransfusion" of blood from the spleen to the circulation, increasing coronary blood flow (CBF) and O2 delivery. We hypothesized that ligation of spleen vessels prior to injection of SV in dogs would prevent the autotransfusion of blood, thereby causing myocardial ischemia due to decreased CBF, simulating the hemodynamic pattern of human envenomation. We studied cardiac output (CO), CBF, left ventricular (LV) O2 delivery and contractility in 11 dogs injected with 0.07 mg/kg of SV (Leiurus quinquestriatus). Ligation of spleen vessels was performed on 6 of the 11 dogs prior to SV injection. 15 min after SV injection CO had increased by 186% in control dogs, while ligation of spleen vessels completely prevented CO elevation (p<0.001). In both groups, however, LV dp/dt increased by 400% and dp/dt/p by 170% (p<0.001). CBF increased by 350% and 550% in the spleen and control groups (p<0.001) respectively. This was associated with elevation of diastolic blood pressure and a decrease in coronary vascular resistance. LV O2 delivery increased (p<0.05) in both groups. At 60 minutes there was a decrease in CO, stroke work, and LV end systolic pressure in both groups, while LV contractility remained above baseline. Scorpion venom injection in dogs causes an initial increase in CO by auto-transfusion of blood from the spleen. Prevention of the autotransfusion does not preclude increases in CBF, O2 delivery and LV contractility.