[Dose-response of intrathecal morphine for post-cesarean analgesia]

Intrathecal morphine for post-operative analgesia is famous for its quality and safety, but its role in post-Cesarean analgesia is not well established. In this study, we investigate its analgesic effect, complication rate and neonatal outcome under various dosages of morphine. The parturients divided into five groups according to morphine dosage: 0, 0.1, 0.25, 0.5, 1.0 mg respectively. The duration of analgesic effect was 19.1 h in 0.1 mg group, 23.6 h in 0.25 mg group, 28.1 h in 0.5 mg group, 30.5 h in 1.0 mg group. Complication rate increased markedly as more than 0.5 mg morphine was injected. Respiratory inhibition (respiratory rate less than 10/min) that required naloxone treatment had occurred twice in 0.5 and 1.0 mg group respectively. Neonatal outcome did not bear any difference among the five groups. In conclusion, adding 0.1 to 0.25 mg morphine to intrathecal anesthetics can be effectively and safely extended into post-Cesarean analgesia.