Objective: Tntrathecal morphine is routinely given for post-cesarean section analgesia. The most serious side effect of
intrathecal morphine in this setting is delayed respiratory depression. The aim of the present study was to investigate the incidence of respiratory depression and other side effects within the first 24 hours after administration of 0.2 mg intrathecal morphine to control post-cesarean section
pain.

Materials and Methods: Electronic medical records of 17,659 parturients who underwent cesarean section under spinal anesthesia with bupivacaine and concurrent administration of 0.2 mg intrathecal morphine to control post-cesarean section pain at Siriraj Hospital during July 2011 to
June 2016 were retrospectively reviewed.

Results: No cases of respiratory depression that required naloxone reversal in the first 24 hours post-cesarean section were observed in the present study. At rest, most patients had a verbal numerical rating score [VNRS] of 1 to 3 (52.8%). During movement, the majority of parturients had a VNRS of 4 to 6 (42.6%). Vomiting and pruritus occurred in 34.7% and 34.5% of patients, respectively. Women with advanced maternal age (>35 years) had significantly lower pain scores both at rest and on movement (p<0.001), significantly less pruritus (p<0.001), but significantly more vomiting (p<0.001) than women aged less than 35 years.

Conclusion: No incidence of delayed respiratory depression was observed among the 17,659 parturients who received 0.2 mg intrathecal morphine to control post-cesarean section pain in the present study. Although the vast majority of patients had good pain control at both rest and during movement, one-third of patients experienced vomiting and/or pruritus.

Keywords: Cesarean section, Tntrathecal morphine, Respiratory depression, Side effects, Spinal anesthesia