[Oral premedication with clonidine in patients undergoing coronary revascularization surgery].

OBJECTIVES

To analyze the effect of premedication with clonidine on level of sedation, anesthetic requirements and hemodynamic repercussions in patients undergoing coronary revascularization.

PATIENTS AND METHODS

Thirty patients were divided into two groups and randomly assigned for premedication with clonidine 0.005 mg/kg p.o. (C) or lorazepam 0.03 mg/kg p.o. (L), along with morphine 0.15 mg/kg i.m. and scopolamine 0.005 mg/kg i.m. in a prospective double-blind study. The level of sedation before surgery and anesthetic requirements in the two groups were compared, as were systolic and diastolic arterial pressure, heart rate and hemodynamics during and after surgery. Fentanyl was used for anesthetic induction in boluses of 0.15 mg every 10 seconds; maintenance boluses of 0.5 mg were used up to a maximum dose of 0.07 mg/kg. If hemodynamic variables analyzed (systolic and diastolic arterial pressure and heart rate) were not kept within 30% of baseline values with this regimen, isoflurane was added.

RESULTS

No differences between the two groups were found for level of sedation. The total dose of fentanyl was lower in group C (0.052 +/- 0.002 mg/kg vs 0.058 +/- 0.002 mg/kg) (p < 0.05). The number of patients requiring isoflurane was similar (4/11 and 6/9) in both groups. The hemodynamic profile prior to extracorporeal circulation (ECC) revealed arterial pressures and heart rates to be lower in the group treated with clonidine (p < 0.05); after ECC systemic resistance in group C was lower (630 +/- 103 vs 795 +/- 106 din.s.cm-5) (p < 0.05) and this was not compensated for by a significant rise in cardiac index (2.62 +/- 0.09 vs 2.40 +/- 0.08 l/min/m2) at similar occlusion pressures.

CONCLUSIONS

Use of clonidine in the type of patient studied does not improve the level of sedation over that achieved with lorazepam. Fentanyl requirements decreased with clonidine. With respect to hemodynamic profile, systemic vascular resistance fell in the clonidine group after removal of ECC, and thus this drug offers no advantages for routine premedication.