Effects of concentration and volume of 2-chloroprocaine on epidural anesthesia in volunteers

Background: Effect of local anesthetic concentration and volume on the spread and density of epidural anesthesia is unclear, This study was performed to delineate effects of a threefold difference in concentration and volume of 2-chloroprocaine on epidural anesthesia. Methods: Twelve healthy volunteers underwent lumbar epidural anesthesia with 300 mg of 2-chloroprocaine as a 3% (10 ml) and a 1% (30 ml) solution in a randomized, double-blind, balanced, crossover fashion. Sensory block was assessed with pinprick, touch (calibrated plastic filament), cold, and electrical stimulation. Motor block was assessed at the quadriceps and gastrocnemius muscles with isometric force dynamometry, Differences between solutions were assessed with repealed measures analysis of variance followed by post hoc testing. Results: The number of dermatomes blocked to pinprick, touch, and cold was significantly greater with the 1% concentration (2 dermatomes greater than the 3% concentration an average, P < 0.05). Similar intensity of sensory block to electrical stimulation developed at the hip and knee and was unaffected by concentration of 2-chloroprocaine. Similar intensity of motor block developed at the quadriceps with both concentrations. Conclusions: Intensity of sensory and motor block from epidural anesthesia with 2-chloroprocaine appears to depend primarily on total milligram dose.