Intravenous but not perineural clonidine prolongs postoperative analgesia after psoas compartment block with 0.5% levobupivacaine for hip fracture surgery

We evaluated the systemic and local effects of clonidine as an analgesic adjunct to psoas compartment block (PCB) with levobupivacaine. In a randomized, prospective, double-blind trial, 36 patients requiring hip fracture surgery received PCB and general anesthesia. Patients were randomized into three groups. Each patient received PCB with 0.4 mL/kg of levobupivacaine 0.5%. The control group (group L) received IV saline, the systemic clonidine group (group IC) received IV clonidine 1 mug/kg, and the peripheral clonidine group (group C) received IV saline and PCB with clonidine 1 mug/kg. The interval from time of completion of block injection to first supplementary analgesic administration was longer in group IC compared with group L (mean +/- SD, 13.4 +/- 6.1 versus 7.3 +/- 3.6 h; P = 0.03). There was no difference between group C and group L (10.3 +/- 5.9 versus 7.3 +/- 3.6 h; P > 0.05). The groups were similar in terms of 24 h cumulative morphine and acetaminophen consumption. There were no significant differences among groups regarding postoperative adverse effects (bradycardia, hypotension, sedation, and nausea). We conclude that IV but not perineural clonidine (1 mug/kg) prolongs analgesia after PCB without increasing the incidence of adverse effects.