Effects of perineural tramadol on sensory and motor conduction of ulnar nerve

Study objective: We aimed to study the effects of perineural tramadol on both sensory and motor conduction of ulnar nerve by electroneurography (ENG).Design: Prospective.Setting: Physical Medicine and Rehabilitation Electrophysiology Laboratory.Patients: Eight healthy volunteers.Intervention: Either 3-mL of saline or 50 mg of tramadol in 3-mL saline was initially administered perineurally to ulnar nerve of nondominant extremity. After two weeks, volunteers who received tramadol were given saline, whereas the ones who received saline were given tramadol.Measurements: Baseline sensory and motor responses of ulnar nerve were recorded by ENG prior to injection of study solutions. Perineural injections were realized by means of a teflon-coated needle and a nerve stimulator. Following injections, sensory and motor responses were monitored every five minutes in the first hour and then every 10 minutes until the sensory and motor amplitudes reached at least 80 percent of the baseline value.Main Results: Perineural tramadol administration showed a significant decrease from baseline measurement in the sensory response amplitude with respect to saline administration (65.9 percent vs 12.7 percent, p < 0.05). Decrease in the motor response amplitudes from baseline versus saline was insignificant (32.9 percent vs 15.2 percent). Sensory block was observed in all of the subjects after tramadol injection when compared with saline administration and lasted 25 minutes (p < 0.05). The duration of motor block lasted 12.5 minutes, and motor block developed in four out of eight subjects when compared with saline administration (p < 0.05). Time to reach maximum sensory and motor block were 15 and 10 minutes, respectively, after tramadol injection.Conclusions: Tramadol has a brief local anesthetic-like action when administered to ulnar nerve perineurally.