Epidural fentanyl speeds the onset of sensory block during epidural lidocaine anesthesia

Background and Objectives: Shortening the onset time of sensory block is a practical goal to improve the quality of epidural anesthesia. The addition of fentanyl to a local anesthetic solution is widely used during epidural anesthesia. This randomized double-blind study examined the onset time of sensory block during epidural lidocaine anesthesia with and without added fentanyl to the epidural solution. Methods: Thirty-six young male patients undergoing knee arthroscopy were randomly allocated into 3 groups of 12 patients each: epidural fentanyl (EF, epidural administration of 17 mL of 2% lidocaine plus 100 mug fentanyl and followed by intravenous (IV) injection of 2 mL of normal saline); IV fentanyl (IF, epidural administration of 17 mL of 2% lidocaine plus 2 mL of normal saline and followed by IV injection of 100 mug of fentanyl); and control (C, epidural administration of 17 mL of 2% lidocaine plus 2 mL of normal saline and followed by IV injection of 2 mL of normal saline). The sensory block was assessed by pinprick method. The hemodynamic changes, postepidural shivering and side effects of epidural fentanyl were also recorded. Results: There was no difference in the distribution of age, weight, and height among the 3 groups. The onset time of sensory block up to T-10 dermatome was significantly more rapid in the EF group (8.3 +/- 3.7 minutes) than that of the IF group (13.1 +/- 4.2 minutes, P <.05) or C group (14.2 +/- 5.4 minutes, P <.05). The upper level of sensory block was also significantly higher in the EF group. Although the incidence of shivering was lower in the EF group, this did not reach statistical significance. Postepidural arterial blood pressures and heart rates were no different among the 3 groups. No nausea, vomiting, pruritus, respiratory depression, urinary retention, or hypotension were observed in any patients. Conclusion: Epidural injection of the mixture of 100 mug fentanyl and 2% lidocaine solution accelerated the onset of sensory block during epidural lidocaine anesthesia without increased side effects.