Material and Method: The present prospective randomized controlled trial was undertaken in 56 pregnant patients that underwent elective cesarean delivery at Siriraj Hospital. All patients were randomized into two groups to receive spinal block with intrathecal morphine as a control group, or direct field block on the top of spinal block with intrathecal morphine as a study group. The assessment of pain score, 24-hour morphine usage, satisfaction score, pruritus, nausea and vomiting, sedation score, and motor power were recorded.

Results: Both groups had similar pain score. The number of subjects who had pain free period during the 24 hours in the direct field block group was seven of 28, while in the control group it was four of 28. Median time of pain free period was 2.10 hours in control group and 2.36 hours in direct field block group. There was no significant difference in 24-hour morphine consumption, satisfaction score, pruritus, nausea, vomiting, and sedation score. Motor power was fully recovered within six hours postoperative in both groups.

Conclusion: Direct field block with 40 ml of 0.125% bupivacaine in conjunction with intrathecal morphine for cesarean section did not increase pain free period or decrease morphine consumption.

Keywords: Direct field block, Cesarean section, Postoperative pain, Pain free period