Modification by preoperative beta-blockade of the renin response to infrarenal aortic cross-clamping.

The activity of the renin-angiotensin system was measured before, during, and after infrarenal aortic cross-clamping in 13 patients. Five of the patients studied were taking propranolol preoperatively and formed a subgroup. Intraoperative blood loss, volume of crystalloid and colloid infused, haemodynamic parameters and urine output were similar for the two groups. In eight patients who were not taking propranolol mean plasma renin activity was 2.24 ng . ml-1 . hr-1 prior to induction, 3.78 ng . ml-1 . hr-1 during surgery prior to cross-clamping and 4.42 ng X ml-1 X hr-1 15 minutes after the aorta was cross-clamped (increases not statistically significant). Mean plasma renin activity measured ten minutes prior to release of the cross-clamp (5.02 ng X ml-1 . hr-1), 15 minutes after clamp release (5.47 ng X ml-1 X hr-1), and 30 minutes after reaching the recovery room (5.84 ng X ml-1 X hr-1) were significantly greater than preinduction levels. Four patients developed postoperative hypertension (mean blood pressure greater than 120 mmHg); there was not a correlation between the elevated plasma renin activity observed postoperatively and the occurrence of postoperative hypertension. The five patients taking propranolol had a markedly attenuated renin activity response during and after surgery; the mean plasma renin activity was less than 1.5 ng X ml-1 X hr-1 at all sampling times. Two of these five patients did develop postoperative hypertension. It is concluded that surgery involving infrarenal aortic cross-clamping is associated with increased plasma renin activity with peak levels occurring postoperatively.(ABSTRACT TRUNCATED AT 250 WORDS)