CHICAGO — Adding clonidine to a local anesthetic hastens the onset of a peripheral nerve block, prolongs the nerve block's effects, and reduces postoperative pain, Dr. Ahmad Elsharydah reported in a poster presentation at the annual meeting of the American Society of Anesthesiologists.
His conclusions came from a metaanalysis of data on 601 adults in 16 randomized, controlled studies that compared the addition of either clonidine or placebo to a single injection of local anesthetic for peripheral nerve block.
Dr. Elsharydah and his associates undertook the meta-analysis because previous studies presented conflicting conclusions about the benefits of adding clonidine to local anesthetics in peripheral and central nerve blocks.
Each of the studies in the meta-analysis was reviewed by three investigators.
The studies did not provide enough data to draw a firm conclusion about the safety of combining clonidine with local anesthetic, but most investigators reported minimal or no adverse reactions, said Dr. Elsharydah of the anesthesia and surgery departments at Louisiana State University, Shreveport.
Dr. Elsharydah has no association with the company that makes clonidine.
Most patients in the 16 studies received peripheral nerve blocks in their upper extremities. The most common local anesthetics used were ropivacaine or mepivacaine; from 0.1 to 3.8 mcg/kg of clonidine was added to the anesthetics.
Pain assessed by visual analog scale scores was significantly lower at multiple points in time after surgery in patients who received clonidine. The clonidine group also needed less postoperative morphine, especially in the first 24 hours, he said.
The time from administration of the peripheral nerve block to the onset of effects was shorter in the clonidine group, and the effects of the block lasted significantly longer than in the placebo group.
Nine of the 16 studies found no difference between groups in the odds of developing hypotension, bradycardia, or sedation, although these findings were not published, Dr. Elsharydah said. Meta-analyses showed that clonidine use was associated with an increased risk of sedation in three studies, a higher risk of hypotension in three studies, and greater odds of bradycardia in three studies.
More well-designed, controlled trials are needed to confirm the findings of this meta-analysis, he said.