Transversus abdominis plane block vs. wound infiltration in Caesarean section: a randomised controlled trial

Multiple studies suggest that transversus abdominis plane (TAP) block (without intrathecal morphine) after Caesarean section (CS) reduces post-operative morphine consumption. In our study, we wanted to compare the analgesic effect of TAP block with infiltration of the wound after CS.

We included 60 pregnant women scheduled for elective CS under spinal anaesthesia in a randomised, single-centre, double-blind study. Thirty patients received ultrasound-guided TAP block using 20 ml bupivacaine 0.25% with adrenaline 5 μg/ml bilaterally and 20 ml normal saline as wound infiltration (TAP group). The other 30 patients (the control group) received normal saline 20 ml bilaterally in the TAP, and 20 ml bupivacaine 0.25% with adrenaline 5 μg/ml as wound infiltration. The main outcome was cumulative morphine consumption at 48 h after surgery. In addition, continuous morphine consumption, pain scores and side effects were registered.

Fifty-seven patients completed the study. Cumulative morphine consumption at 48 h (mean±standard deviation) was 41±34 mg in the TAP group and 38±27 mg in the control group (P=0.7); a difference of 3 mg (95% confidence interval -13 to 19 mg). Morphine consumption at any time up to 48 h was virtually identical in both groups. Side effects were similar, except for a higher degree of sedation in the TAP group (P=0.04).

Compared with wound infiltration with local anaesthetics, TAP block did not reduce cumulative morphine consumption following CS. The TAP block was associated with more pronounced sedation.