RESUMEN

Perioperative analgesia for cesarean section aims to ensure the mother's comfort, facilitate a smooth surgical experience, and promote a successful recovery. One-hundred-ninety patients were enrolled in a randomized double-blind study designed to assess the quality of perioperative analgesia, level of satisfaction, and incidence of adverse reactions in elective cesarean section under spinal anesthesia when fentanyl or morphine was added to bupivacaine. Two treatment groups comprising 173 subjects were compared in the per-protocol analysis: F (fentanyl, standard dose 25 µg) and M (morphine, standard dose 100 µg). Numerical pain scores were recorded perioperatively for 72 h (both at rest and on mobilization), with overall postoperative satisfaction and analgesic-related side effects. The patients in the morphine group had significantly better pain management (Mann-Whitney U test, p < 0.001) and higher level of satisfaction (Mann-Whitney U test, p < 0.001). The latter was related to the greater need for rescue medication in the fentanyl group (OR = 4.396; p = 0.019). On the other hand, fentanyl had significantly fewer non-life-threatening side effects, such as high-intensity pruritus (Mann-Whitney U test, p < 0.001), nausea (OR = 0.324; p = 0.019), vomiting and dizziness upon first mobilization (OR = 0.256; p < 0.001). It remains for future clinical trials to help establish doses that will tilt the scale to one side or the other.