Effect of warm lidocaine on the sensory onset of epidural anesthesia: A randomized trial

Background: Administration of local anesthetics at body temperature has been reported to shorten the onset time of regional block; however, studies examining the effects of warmed lidocaine on the onset of epidural anesthesia are limited. Here, we ascertain whether warming lidocaine solution to body temperature shortens the time to onset of epidural anesthesia. Methods: Eighty patients were randomly allocated into two groups of equal size. Both received 16 ml of lidocaine solution injected via the epidural route at the L4-5 interspace, with one group receiving the solution at room temperature (RT, 18° C) and the other receiving the solution warmed to body temperature (BT, 36° C). Sensory blocks at the T10, T12, and L3 dermatomes, perianal region, and upper level dermatomes were assessed by pinprick and their onset times recorded. Patients with incomplete anal sensory block were excluded. Results: Seventy-seven patients were included for analysis. The pH value of the local anesthetic solution was significantly increased at BT compared to RT (6.57 ± 0.11 vs. 6.47 ± 0.11, p < 0.05). Significantly shorter onset times of sensory block were observed at the T12 (10.03 ± 3.55 vs. 11.71 ± 3.76 min) and L3 (7.49 ± 3.19 vs. 9.92 ± 3.46 min) dermatomes for the BT compared to the RT group (p < 0.005). The onset time of sensory block at the anal region was also shorter in the BT than the RT group (11.54 ± 4.35 vs. 12.50 ± 4.06 min, p < 0.05). No differences between groups with respect to gender, age, height, weight, visual analogue pain score, upper sensory level, or adverse events were observed. Conclusions: Administration of lidocaine at BT compared to RT shortens the onset time of sensory block in epidural anesthesia with no associated adverse effects.