Objectives: The aim of this randomized double-blind study was to investigate whether 20 μg of intrathecally administered fentanyl would influence the incidence and severity of shivering in patients undergoing cesarean section.
Material and Method: Sixty healthy patients scheduled for cesarean section under spinal anesthesia using 2.2 ml of 0.5% hyperbaric bupivacaine with 0.2 ml of morphine 0.2 mg, were randomly allocated to receive an additional 0.4 ml of fentanyl 20 mg intrathecally (Group F) or normal saline 0.4 ml (Group S).
Results: The incidence of shivering three hours after spinal anesthesia was 6 of 30 patients, 20% in Group F and 15 of 30 patients, 50% in Group S. The difference was statistically significant (p < 0.05). Almost all of the shivering patients started in their first hour after spinal anesthesia (5 patients in Group F and 13 patients in Group S). None in Group F but 4 patients in Group S started shivering before their babies were delivered. The shivering score was also significantly lower in Group F (p < 0.05). Treatment for shivering was requested in 16% and 26% of the shivering patients in Group F and Group S, respectively. There was no difference in the incidence of pharmacologic side effects. The core temperature did not differ significantly between the groups during 3 hours after spinal anesthesia.
Conclusion: The addition of 20 μg fentanyl in 2.2 ml of 0.5% hyperbaric bupivacaine with 0.2 ml of morphine 0.2 mg intrathecally can reduce the incidence and severity of intraoperative and postoperative shivering after spinal anesthesia for patients who were receiving cesarean section without increasing other side effects.

Keywords: Intrathecal opioid, Postoperative, Shivering, Fentanyl, Cesarean section