Hemodynamic effects following injection of venom from the scorpion Leiurus quinquestriatus

Abstract

Purpose : The present study tested the hypothesis that scorpion sting induces left ventricular (LV) hypokinesia and myocardial ischemia shortly after injection due to reduction of coronary blood flow (CBF) and increased oxygen demand. Methods : In 5 mechanically ventilated, open-chest dogs, we measured LV function following IV injection of venom (0.05 mg/kg) obtained from the scorpion Leiurus quinquestriatus. Hemodynamic responses to the venom were followed up for 90 minutes. Results : The venom induced significant combined respiratory and metabolic acidosis (arterial pH progressed from 7.35 ± 0.03 at baseline to 7.10 ± 0.06 at 90 minutes). There were large increases in blood pressure, LV end systolic pressure, stroke work, and velocity of contraction. Twenty minutes following venom injection, cardiac output (CO) increased by 37% but then declined to 36% below baseline by 90 minutes ( P < .05). CBF increased significantly in proportion to increased perfusion pressure; hence, there was no change in coronary vascular resistance. There was no evidence of myocardial ischemia or LV dysfunction because there was no change in myocardial pH, percentage fiber shortening, or LV end-diastolic pressure. Despite the fact that some variables returned to baseline at 90 minutes, they did not reach steady state; thus, the preparation would have continued to deteriorate. Conclusions : Myocardial ischemia does not occur in this dog model immediately following administration of scorpion venom. There are significant peripheral circulatory effects of the venom, which account for many of the hemodynamic changes.