Effects of Intra-Operative Intravenous Clonidine on Cardiovascular Responses to Extubation

Do, Young Woo; Seok, Ce Hong; Kim, Sae Yeon; Kim, Heung Dae

Abstract

Increases in heart rate (HR) and blood pressure (BP) are common during light planes of anesthesia at the end of operation and just prior to extubation. This study was undertaken to investigate and compare HR and BP responses to endotracheal extubation during light general anesthesia with and without prior intravenous administration of clonidine. Eighty hypertensive patients aged 45-65 yr were undergoing a variety of operations. In this study, the BP of hypertensive patients was well controlled on antihypertensive regimens before anesthesia. Anesthesia was induced by the injection of thiopental sodium, diazepam, fentanyl and vecuronium, and maintained with enflurane (0.8-2.5 per cent) and nitrous oxide (50 per cent) in oxygen. Patients were randomly divided into two groups of 40 each with regard to management of endotracheal extubation at the end of operation. Patients in clonidine group received an izv injection of clonidine (0.75 ug/kg) 30 min. prior to extubation. One minute prior to extubation, baseline arterial BP and HR were recoreded. Single measurement of systolic and diastolic BP and HR were obtained during the study and were recorded at 30 seconds, 1 min., 2 min., 3 min., 4 min. and 5 min. after extubation, and upon entrance to the postanesthetic recovery room (6-10 min. after extubation). Patients in control group received no injection prior to extubation, but were otherwise treated similarly and had data recorded at the same times as those in clonidine group. The results were as follows ;1) No significant differences were noted in BP and HR prior to clonidine administration between patients in the two groups. 2) Thirty seconds after extubation, both BP and HR increased significantly in both group (p< 0.05) but the increasing rate in clonidine group was significantly less than in control group (p<0.05). 3) Patients in control and clonidine group sustained a significant elevation in both BP and HR which persisted for 3 and 1 min after extubation (p<0.05), respectively. 4) Changes in both BP and HR in patients of clonidine group became significantly less than control group every time intervals after extubation (p<0.05). In conclusion, the result of this study demonstrate that iv injection of clonidine (0.75 ug/kg) administered 30 min. before endotracheal extubation prevents increases in BP and HR before and after extubation and in the recovery room. The data suggest that iv clonidine injection prior to extubation should be of advantage to patients with hypertension who may not be able to tolerate the increased hemodynamics which usually accompany endotracheal extubation.