RESUMEN
BACKGROUND: Single-shot spinal analgesia with bupivacaine and a short-acting opioid for labour pain is popular due to its simplicity, rapid onset, and profound analgesia without significant motor block. Its limitation is the short duration of action. Supplementation with intrathecal morphine has been shown to prolong analgesia. We compared the addition of placebo or morphine 50 or 100 µg to intrathecal bupivacaine and sufentanil to evaluate the impact on duration of labour analgesia. METHOD: Following ethics committee approval and verbal and written patient consent, 90 healthy nulliparous women were included in the study. As part of a combined spinal-epidural technique, women were randomised to receive intrathecal bupivacaine 1.25mg and sufentanil 5 µg with morphine 50 µg, 100 µg or saline placebo in a double-blind fashion. Onset of analgesia was measured as the time from intrathecal injection to a visual analogue scale pain score < or =4 (scale 0-10) and the duration of analgesia as the time from intrathecal injection to the return of pain >4. RESULTS: No significant differences between the groups were seen in onset or duration of analgesia, side effects or obstetric and neonatal outcome. CONCLUSION: The addition of 50 or 100 µg morphine to 1.25mg bupivacaine and 5 µg sufentanil during established labour did not significantly increase the duration of analgesia.