Effects of intrathecal clonidine on duration of bupivacaine spinal anaesthesia, haemodynamics, and postoperative analgesia in patients undergoing knee arthroscopy.

Clonidine, an alpha-2-adrenergic agonist, may have a clinically relevant analgesic action but also a hypotensive action, when administered spinally. In this study, therefore, the analgesic and circulatory effects of intrathecal clonidine were studied in patients undergoing knee arthroscopy under spinal anaesthesia. Forty ASA I-II patients were randomly divided to two groups. One group received clonidine 3 micrograms.kg-1 mixed with 15 mg 0.5% bupivacaine and the other group an identical saline volume mixed with bupivacaine as above, in a double-blind fashion. Sensory analgesia, blood pressure, heart rate and sedation were followed during and after the operation. Oxycodone 0.14 mg.kg-1 i.m. or ketoprofen 100 mg p.o. was administered when needed. The duration of sensory analgesia (until regression of the block to L2) was longer in the clonidine group (mean 217 min) than in the control group (mean 160 min) (P < 0.05). Duration of motor blockade was also longer in the clonidine group (mean 215 min) compared to the control group (161 min) (P < 0.05). Mean arterial pressure and heart rate were significantly lower in the clonidine group compared to the control group. The clonidine patients needed fewer supplemental doses of oxycodone (8 doses) than those in the control group (16 doses) (P < 0.05). More patients in the clonidine group were sedated 3-6 h after the injection (P < 0.05). Addition of clonidine prolonged the bupivacaine spinal block. However, marked haemodynamic changes and sedation may limit the usefulness of intrathecal clonidine.