Background: Spinal anesthesia can be associated with hemodynamic changes and some other complications. The aim of this study was to evaluate the effect of adding fentanyl to lidocaine on the spinal anesthesia time and its complications for cesarean section.

Methods: Sixty pregnant women with gestational age of 37- 42 weeks and ASA physical status I and II undergoing elective cesarean section under spinal anesthesia were enrolled in a randomized double blinded clinical trial. They were randomly allocated to receive spinal anesthesia with lidocaine-normal saline (LS: 75 mg lidocaine 5% with 0.3 ml normal saline) lidocaine-fentanyl (LF) group (75 mg lidocaine 5% with 50 μg fentanyl). The duration of initiation of sensory block to achieve T4 level, time to return of sensory level to T12, time to first analgesic request, ephedrine requirement, nausea and vomiting during and after the surgery, pruritus, respirator depression, headache and apgar score of the new born  at 1st and 5th minutes were assessed.

Results: There was no significant difference between time to achieve T4 level, ephedrine dose, post operative nausea and vomiting (PONV), pruritus and headache in study groups. Time to return of sensory level to T12 was significantly longer in LF group (152.6±14.7 vs. 66.2±11.2 min, P=0.0009). Time to first analgesic request was also longer in LF group (164.2±20.8 vs. 68.1±11.3 min, P=0.0009). The incidence of nausea and vomiting during surgery was significantly more in LF group (20% vs. 0%, P=0.023). No case of respiratory depression was observed in groups.The 1st and 5th minute's apgar score were comparable between groups and were between 7 and 10.

Conclusions: Addition of fentanyl to intrathecal lidocaine in patients undergoing elective cesarean section results in increasing of the block duration and time to first analgesic request without significant maternal or neonatal side-effects, without effect on 1st and 5th minutes apgar score  with increasing the incidence of during surgery nausea and vomiting.