Cardiovascular Response, Analgesic and Sedative Effect according to the Dose of Epidural Clonidine

Kweon, Kwang Jun; Lee, Seung Joon; Choi, Hyun; Kil, Ho Yeong; Yoon, Young Joon

Abstract

The subarachnoidal or epidural opioid reveals excellent analgesic effect for postoperative pain and intractable cancer pain, but its side effects such as nausea, vomiting, voiding difficulty, pruritus and respiratory failure limit its use. There were many studies for decreasing frequency and severity of side effects and reinforcing the analgesic effect of opioid by administrating other drugs. Clonidine is one of such drugs which is able to be administered epidurally with opioids for that purpose. We studied the changes of cardiovascular response, analgesic and sedative effect according to the dose of epidural clonidine. The analgesic effect of epidural clonidine was investigated in 30 patients who underwent anal surgery with epidural anesthesia using 15 ml of 1.5~2 % lidocaine.The time of maximal intensity of pain after disapperance of injected lidocaine was checked. Thirty patients were divided into three groups randomly. In group 1 (n=10), the dose of epidural clonidine was 50 ug; Group 2 (n=10) was 150 ug; Group 3 (n=10) was 450 ug. Changes in the arterial pressure, pulse rate, sedation state and SpO2 were observed before and during 60 minutes after epidural clonidine administration. And the analgesic effect was assessed by measuring VAS pain score. Blood pressures and pulse rates decreased according to increase of dosage of clonidine. Group 1 showed the analgesic effect of 34%, group 2 showed 77% and group 3 showed 81% at 60 minutes after administration. Sedation effect was seen in group 2 and 3 but SpO2 was not decreased significantly. We thought that the respiratory depression of epidural clonidine was not so significant to limit the use for the postoperative pain control. We conclude that it is better to administer clonidine with opioids epidurally than clonidine slone to get better analgesic effect and less sedative effect, because the analgesic effect of epidural clonidine increases according to increase of dosage but the sedative effect increases also.