[Effects of intramuscular and perineural clonidine on sciatic nerve block with 0.5% ropivacaine.].

BACKGROUND AND OBJECTIVES This study evaluated the effects of clonidine on anesthesia onset, quality and duration of analgesia of sciatic nerve block using 0.5% ropivacaine. METHODS Forty adult patients scheduled for foot or lateral aspect of the ankle procedures under combined anterior femoral/sciatic nerves block were randomly assigned to group 1, receiving 25 mL of 0.5% ropivacaine plus placebo perineurally, group 2, receiving intramuscular 2 microg.kg-1 clonidine and perineural 25 mL of 0.5% ropivacaine and group 3, receiving perineural 2 microg.kg-1 clonidine and 25 mL of 0.5% ropivacaine injected after motor responses were obtained with stimulations between 0.2 and 0.5 mA. Sensory and motor blocks were assessed for 30 minutes after blockade. A total block effectiveness score was calculated. The quality of surgical anesthesia was classified as success or failure according to the need for systemic intraoperative supplementation. Duration of anesthesia was defined as time from blockade placement until the first analgesic request. RESULTS Median onset times were 5, 12.5, and 17.5 minutes for groups 1, 2 and 3, respectively (p = 0.11). Success rates were 100%, 93% and 75% (p = 0.12), and postoperative analgesia duration was 14.5, 13.5 and 13.75 hours (p = 0.15) for groups 1, 2 and 3, respectively. CONCLUSIONS Intramuscular or perineural clonidine has not affected anesthetic onset, quality or the duration of postoperative analgesia of 0.5% ropivacaine-induced sciatic nerve block.