Effect of clonidine on the circulation and vasoactive hormones after aortic surgery

Abstract

After completion of abdominal aortic graft, 29 patients received an i.v. infusion of placebo (n = 16) or clonidine 7 μg kg-1 (n = 13) over 120 min in a double-blind study. Cardiovascular variables were measured and plasma samples obtained up to 5 h after arrival in the recovery room, for assay of noradrenaline, adrenaline, vasopressin and renin concentrations. Noradrenaline, adrenaline and vasopressin concentrations decreased in the clonidine group throughout recovery (P < 0.001, 0.05 and 0.05, respectively, vs placebo). Heart rate was less in the clonidine group (P < 0.01). There was no significant difference in mean arterial pressure between groups. Stroke volume was larger (P < 0.01) and there were fewer episodes of hypertension (P < 0.05) and tachycardia in the clonidine group. In addition, a reduction in the number of circulatory interventions (P < 0.05) and episodes of shivering was noted in the clonidine group. Mean (SD) postoperative volume requirements were larger in the clonidine group (total postoperative input: clonidine 1462 (604) ml; placebo 1064 (348) ml (P < 0.05)). These data are consistent with the observation that clonidine modifies endocrine and circulatory status after major surgery. © 1991 British Journal of Anaesthesia.