Supraceliac aortic cross-clamping and declamping. Effects of dopexamine and dopamine on systemic and mesenteric hemodynamics, metabolism and intestinal tonometry in a rat model.

Abstract

The effects of dopexamine and dopamine on mesenteric ischemia during reperfusion following aortic cross-clamping are not known. We determined intramucosal tonometric PCO2 and PCO2 gap using a rat model of supraceliac aortic cross-clamping and declamping. Under pentobarbital and fentanyl anesthesia, 24 rats were surgically instrumented with arterial, right atrial, and portal venous catheters, ultrasonic flowprobes for measurements of abdominal aortic, superior mesenteric and carotid artery blood flow, and a pediatric tonometer for intestinal mucosal PCO2 measurements. Rats were randomized to receive a continuous infusion of dopexamine (10 x microg(-1) x kg(-1) x min(-1), n=8), dopamine (10 microg x kg(-1) x min(-1), n=8 ), or physiologic saline (control, n= 8), infused at a rate of 4 ml x kg(-1) x h(-1), administered throughout the experimental protocol. After 30 min of drug infusion, the aorta was cross-clamped at the supraceliac level for 30 min. Reperfusion following declamping was observed for 180 min. Intestinal tonometric PCO2 remained unchanged during drug treatment before aortic cross-clamping, increased similarly in all groups following declamping during early reperfusion, and recovered to baseline within 30 min of reperfusion. Dopexamine treatment was associated with higher lactate levels and increased heart rate (P<0.05) during aortic cross-clamping. 1) Mesenteric ischemia, determined by intestinal tonometric PCO2 and PCO2 gap, recovers within 30 min of reperfusion following 30 min of aortic cross-clamping irrespective of drug treatment and, 2) dopexamine induced higher lactate levels and increased heart rate during aortic cross-clamping and should be carefully analyzed for potentially adverse effects on cardiac function.