Brachial plexus nerve block exhibits prolonged duration in the elderly

Upper limb trauma occurs frequently in elderly patients for whom peripheral nerve blocks are often preferred for anesthesia. The characteristics of such regional blocks have, however, never been described in an elderly population. Therefore, the authors assessed prospectively the onset and duration of upper extremity peripheral nerve block (the mid-humeral block) in elderly and young patients undergoing emergency upper extremity surgery.

Consecutive patients aged > 70 yr or < 70 yr received a mid-humeral block with a small volume of ropivacaine, 0.75%. Five milliliters was injected onto each of the musculocutaneous, radial, ulnar, and median nerves. Time to complete sensory and motor block and durations of complete sensory and motor block were assessed. Results are shown as median and its 95% confidence interval.

Median ages were 77 yr (95% CI, 72-81 yr) and 39 yr (95% CI, 27-46 yr) in the two groups. Both groups had similar times to complete sensory blockade. The elderly group had longer durations of complete sensory (390 min [range, 280-435 min] vs.150 min [range, 105-160 min]; P< 0.05) and motor (357 min [range, 270-475 min] vs. 150 min [range, 90-210 min]; P< 0.05) blockade. Duration of complete sensory block was significantly correlated with age (rho = 0.56; P< 0.05).

Age is a major determinant of duration of complete motor and sensory blockade with peripheral nerve block, perhaps reflecting increased sensitivity to conduction failure from local anesthetic agents in peripheral nerves in the elderly population.