Effects of vasopressin on left anterior descending coronary artery blood flow during extremely low cardiac output

Abstract

Because of the possibility of vasopressin-mediated coronary vasospasm, this study was designed to assess effects of vasopressin compared to saline placebo on left anterior descending (LAD) coronary artery blood flow. Twelve anaesthetized domestic swine were prepared for LAD coronary artery blood flow measurement with ultrasonic flow probes, using cardiopulmonary by-pass adjusted to 10% of the prearrest cardiac output. This 10% value approximates that reported for cardiac output during conventional closed-chest CPR. After 4 min of untreated ventricular fibrillation, and 3 min of cardiopulmonary by-pass blood flow, 12 pigs were randomly assigned to receive intravenously, every 5 min, either vasopressin (0.4, 0.4, and 0.8 U/kg; n = 6) or saline placebo (n = 6). The mean +/- S.D. LAD coronary artery blood flow in the vasopressin and placebo pigs was comparable before cardiac arrest, and during cardiopulmonary by-pass low flow; but increased significantly (P < 0.05) 90 s after each of three vasopressin injections compared to placebo (78 +/- 1 versus 42 +/- 2 ml/min; 62 +/- 2 versus 36 +/- 1 ml/min; and 54 +/- 1 versus 27 +/- 1 ml/min), respectively. Coronary vascular resistance decreased significantly (P < 0.05 ) 90 s after each of three vasopressin and placebo injections. In this model, repeated bolus administration of vasopressin, given during simulated extremely low cardiac output improved LAD coronary artery blood flow to prearrest levels without affecting coronary vascular resistance.

Conclusions: during extremely low blood flow using cardiopulmonary by-pass, vasopressin improves LAD coronary artery blood flow without affecting coronary vascular resistance.