Background There is controversy about the effectiveness of perineural clonidine used as an adjuvant to local anesthetics. This study investigated whether the addition of 150 μg clonidine to 0.5% levobupivacaine used for posterior sciatic nerve block would prolong the duration of analgesia.

Methods This double-blind, prospective trial compared the analgesic characteristics of 20 mL plain levobupivacaine versus 20 mL levobupivacaine 0.5% plus 150 μg clonidine in a posterior sciatic nerve block (Labat approach) for foot and ankle surgery. Sixty patients were randomized and allocated to receive either levobupivacaine alone or levobupivacaine plus clonidine, to find a 30% prolongation of analgesia with the adjuvant, using the same SD. The onset and duration of the block (time from completion of block administration to first morphine request), the hemodynamic changes during surgery, the need for rescue analgesia, and technical or neurologic complications were assessed over a 24-hour period.

Results The onset of sensory block (in minutes) was similar in the levobupivacaine and levobupivacaine plus clonidine groups (10 [5–20] vs 10 [5–23] minutes, median [interquartile range], respectively), as was the time to first request of pain medication (1215 [920–1530] vs 1275 [1067–1360] minutes, respectively). However, during surgery, statistically significantly more subjects in the levobupivacaine plus clonidine group than the levobupivacaine group experienced a decrease of more than 20% in systolic arterial pressure (50% vs 28% of patients, respectively; P < 0.028). No complications were noted in either group over 24 hours.

Conclusions Addition of 150 μg clonidine to 20 mL of levobupivacaine 0.5% in posterior gluteal (Labat) sciatic nerve block did not prolong the duration of analgesia but had a slight effect on systolic arterial pressure.