SPINAL CLONIDINE FAILS TO PROVIDE SURGICAL ANESTHESIA FOR TRANSURETHRAL RESECTION OF PROSTATE - A DOSE-FINDING PILOT-STUDY

Background and Objectives. This study was designed to determine whethe r subarachnoid clonidine administration alone results in surgical anes thesia for transurethral resection of the prostate. Methods. Blood pre ssure, heart rate, sedation, and sensory and motor blocks were assesse d in 12 patients before and after lumbar subarachnoid injection of inc reasing doses of clonidine (three patients each received 75, 150, 300, and 450 mu g doses). General anesthesia was induced at the request of the patient or surgeon, if conditions were unsatisfactory. Results. C lonidine resulted in marked sedation within a mean of 19 minutes of sp inal injection, and no motor block was observed. There was a 25% (rang e, 0-45%) reduction in mean arterial blood pressure. Although endoscop y was tolerated in all cases, general anesthesia was required when res ection began, except in two patients who received 300 and 450 mu g of clonidine, respectively. Postoperative analgesic requirements showed w ide interindividual variability (mean, 6 hours; range 2-12 hours). Con clusions. Subarachnoid clonidine cannot be reliably used as the sole a gent for spinal anesthesia, since general anesthesia is often required or deep sedation occurs. Increasing doses of clonidine do not prolong postoperative analgesia. Thus, clonidine could be used as a spinal an algesic but not as a spinal anesthetic.