Comparative study of epidurally administered clonidine and buprenorphine on anesthetic requirement and electroencephalographic activity.

The author investigated the effects of epidurally administered buprenorphine (BPN) and clonidine (CLO) on the potentiation of halothane anesthesia in terms of the minimum alveolar concentration (MAC), hemodynamics, and electroencephalographic activity in the patients undergoing lower abdominal surgery. Thirty-four women (ASA-1) were studied after the epidural administration of either 10 ml saline (group A, n = 8), 10 ml saline with 0.4 mg BPN (group B, n = 13), or 10 ml saline with 150 micrograms CLO (group C, n = 13). The MAC of halothane was reduced by 32% in group B (p < 0.05), and by 23% in group C (p < 0.05) compared with group A. The delta activity on the electroencephalogram (EEG) was more dominant in groups B and C 20 and 30 minutes after the administration of BPN and CLO compared with group A. The alpha activity in group A was significantly greater than that in the other groups. The delta activity in groups B and C was increased significantly compared with group A. The blood pressure was significantly lower after the epidural administered of CLO in group C, compared with groups A and B. The study concluded that epidurally administered CLO significantly reduce the MAC of halothane and also resulted in significant acceleration of delta activity on the EEG, as did BPN. The mechanisms by which the central nervous system (CNS) is depressed by epidural BPN and CLO are different, but this may have resulted from their direct action on the CNS via the systemic and spinal absorption of BPN and CLO.