COMPARISON OF CLONIDINE, MORPHINE OR PLACEBO MIXED WITH BUPIVACAINE DURING CONTINUOUS SPINAL-ANESTHESIA

Purpose: To compare intraoperative anaesthetic and haemodynamic effect s of clonidine-bupivacaine, morphine-bupivacaine and placebo-bupivacai ne combinations during continuous spinal anaesthesia, Methods: Thirty six geriatric patients, undergoing knee replacement using continuous s pinal anaesthesia were randomly assigned to: Placebo (n = 12), clonidi ne (n = 12) and morphine (n = 12), where 1 ml saline, 0.15 mg clonidin e or 0.15 mg morphine were mixed with 10 mg bupivacaine 0.5%. Anaesthe tic variables studied were maximal sensory level and degree of motor b lock, duration of surgical analgesia and duration of anaesthesia. Chan ges in systolic arterial pressure and vasopressor requirements were ev aluated, Results: Maximal sensory level and degree of motor block were comparable among the groups. Before surgery two patients in the place bo group, three in the clonidine and one in the morphine group receive d one additional mi bupivacaine 0.5% because of inadequate anaesthesia and were not considered for determination of duration of surgical ana lgesia. In the remainder, 1/9 in the clonidine group, 8/10 in placebo and 8/11 in morphine (P < 0.05) received reinjection of bupivacaine fo r surgical pain, These injections were given about 2 1/2 hr after the initial intrathecal injection, the duration of anaesthesia being about four hours. During the first 30 min after the initial injection the d ecrease in systolic pressure was greater in the clonidine and morphine than in the placebo group (P < 0.05). Thereafter, vasopressor require ments were higher only in the clonidine group (P < 0.05). Conclusion: In elderly patients 0.15 mg clonidine but not 0.15 mg morphine prolong ed surgical analgesia when added to 10 mg plain bupivacaine.