Perioperative effects of systemic or spinal clonidine as adjuvant during spinal anaesthesia
Abstract: Aim of study: To evaluate the effects of different doses of clonidine administered systemically or spinally in combination with local anaesthetics on sensory and motor block intraoperatively, on pain relief postoperatively, and on the incidence of postoperative alcohol withdrawal syndrome (AWS) in alcohol abusers.Patients and methods: A total 285 patients were included in five studies. In two studies, oral clonidine (150 and 300 µg) or intrathecal clonidine (100 and 150 µg) was combined with local anaesthetics to evaluate the quality of sensory and motor block and postoperative analgesia. In a third study, the ant-idelirious effect of a single dose of clonidine (150 µg) given orally or intrathecally before operation was studied in 45 heavy alcohol abusers (daily ethanol intake of at least 60 g). The combination oflow doses of clonidine (15 and 30 µg) intrathecally with low dose bupivacaine was investigated during ambulatory herniorrhaphy. In a combined spinal-epidural anaesthesia study, a moderate dose of postoperative epidural clonidine (40 µg/h) was studied with or without low dose intrathecal clonidine (15µg); plain local anaesthetic was used as control. Sensory block was assessed by pin-prick, light touch, thermotest and transcutaneous electric stimulation; motor block was estimated by a modified Bromage scale. Pain intensity according to a Visual Analogue Scale (VAS) and analgesic request were recorded. AWS was assessed by the criteria of the Diagnostic and Statistical Manual of Mental Disorders.Results: Intraoperatively, high doses of oral or intrathecal clonidine added to local anaesthetics almost doubled the time of sensory and motor block, and it was possible to reduce the dose of local anaesthetics without diminishing of the quality of spinal anaesthesia. Low doses of clonidine (15 µg) in combination with a low dose of bupivacaine significantly increased the spread of analgesia (4 dermatomes) without significantly prolonging the motor block. The same dose of clonidine combined with a high dose of bupivacaine significantly prolonged the sensory- and motor block by 36% and 18%, respectively Postoperatively, both oral and intrathecal clonidine prolonged time to first analgesic request. V AS score was acceptably low in all study groups. However, a high dose (150 µg) of intrathecal clonidine reduced postoperative 24-hour morphine consumption by 40% compared with control, while morphine-sparing was 55% when a low dose (15 µg) of intrathecal clonidine was combined with epidural clonidine. In ambulatory practice, low doses of intrathecal clonidine decreased analgesic requirements at home for up to 24 h after operation. In comparison with diazepam premedication, clonidine 150 µg, intrathecally or orally, reduced the incidence and degree of postoperative AWS in alcohol-dependent men (from 80 to 10%). The major side-effects of clonidine were hypotension and sedation, especially after oral administration. This hypotensive effect was also found after epidural clonidine infusion.Conclusion: Clonidine, as an adjuvant to local anaesthetics, provided a higher quality of anaesthesia and postoperative analgesia and prevented postoperative alcohol withdrawal syndrome in alcohol abusers. Side effects such as hypotension and pronounced sedation postoperatively should be kept in mind if high doses of clonidine are used.
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