Analgesic efficacy of intrathecal fentanyl during the period of highest analgesic demand after cesarean section: A randomized controlled study.

Cesarean section (CS) is one of the most common surgical procedures in female patients. We aimed to evaluate the postoperative analgesic efficacy of intrathecal fentanyl during the period of greatest postoperative analgesic demand after CS. This period was defined by detailed analysis of patient-controlled analgesia (PCA) usage.This double-blind, placebo-controlled, parallel-group randomized trial included 60 parturients who were scheduled for elective CS. Participants received spinal anesthesia with bupivacaine supplemented with normal saline (control group) or with fentanyl 25 μg (fentanyl group). To evaluate primary endpoints, we measured total pethidine consumption over the period of greatest PCA pethidine requirement. For verification of secondary endpoints, we recorded intravenous PCA requirement in other time windows, duration of effective analgesia, pain scores assessed by visual analog scale, opioid side effects, hemodynamic changes, neonatal Apgar scores, and intraoperative pain.Detailed analysis of hour-by-hour PCA opioid requirements showed that the greatest demand for analgesics among patients in the control group occurred during the first 12 hours after surgery. Patients in the fentanyl group had significantly reduced opioid consumption compared with the controls during this period and had a prolonged duration of effective analgesia. The groups were similar in visual analog scale, incidence of analgesia-related side effects (nausea/vomiting, pruritus, oversedation, and respiratory depression), and neonatal Apgar scores. Mild respiratory depression occurred in 1 patient in each group. Fewer patients experienced intraoperative pain in the fentanyl group (3% vs 23%; relative risk 6.8, 95% confidence interval 0.9-51.6).The requirement for postoperative analgesics is greatest during the first 12 hours after induction of anesthesia in patients undergoing CS. The addition of intrathecal fentanyl to spinal anesthesia is effective for intraoperative analgesia and decreases opioid consumption during the period of the highest analgesic demand after CS, without an increase in maternal or neonatal side effects. We recommend using intrathecal fentanyl for CS in medical centers not using morphine or other opioids intrathecally at present.