AORTIC-SURGERY - EFFECT OF CLONIDINE ON INTRAOPERATIVE CATECHOLAMINERGIC AND CIRCULATORY STABILITY

Twenty‐eight patients presenting for aortic surgery were randomly assigned in a double‐blind, placebo‐controlled protocol to receive placebo (n=14) or clonidine (4.7 ± 1.2 μg · kg‐1 po; n=14), in addition to flunitrazepam 120 min before induction of anesthesia. Plasma catecholamines (CA) and hemodynamic variables were determined at 7 stages during surgery. In the placebo group, plasma epinephrine (E) and norepinephrine (NE) had risen twofold at skin closure compared to baseline (E: from 109 ± 51 pg p ml‐1 to 294 ± 161 pg · ml‐1; NE: from 658 ± 226 to 1150 ± 494 pg · ml‐1). Plasma CA were significantly lower in the clonidine group (P<0.001 and 0.01 vs placebo for NE and E respectively). In both groups, similar directional changes were observed for the circulatory variables, upon aortic clamping and declamping. In the clonidine group, however, mean arterial pressure was lower at most stages (P<0.05 vs placebo); moreover, stroke volume index was greater in the clonidine group (P>0.05) upon declamping. This improved stability in the clonidine group was achieved with a halving in the number of anesthetic/circulatory interventions (P >0.05 vs placebo). Provided intravascular volume is adequate, clonidine suppresses the increase in plasma catecholamines induced by aortic surgery and improves circulatory stability, with a reduced number of anesthetic/ circulatory adjustments. © 1990 Acta Anaesthesiologica Scandinavica Fonden