Transversus Abdominis Plane Block Versus Wound Infiltration for Analgesia After Cesarean Delivery: A Randomized Controlled Trial

BACKGROUND: Transversus abdominis plane (TAP block and local anesthetic wound infiltration provide analgesia after cesarean delivery. Studies comparing the 2 techniques are scarce, with conflictifig results. This double-blind, randomized controlled trial aimed to compare bilateral ultrasound-guided TAP block with single-shot local anesthetic wound infiltration for analgesia after cesarean delivery performed under spinal anesthesia. We hypothesized that the TAP block would decrease postoperative cumulative fentanyl consumption at 24 hours. METHODS: Eligible subjects were American Society of Anesthesiologists physical status II parturients with full-term singleton pregnancies undergoing elective cesarean delivery under spinal anesthesia. Exclusion criteria were: <19 years of age or >40 years of age; height <150 cm, weight <60 kg, body mass index >= 40 kg/m(2); Contraindications to spinal anesthesia; history of recent opioid exposure; hypersensitivity to any of the drugs used in the study; significant cardiovascular, renal, or hepatic disease; and known fetal abnormalities. Eighty subjects were randomly allocated to 2 equal groups. In the infiltration group, participants received 15 mL of bupivacaine 0.25% in each side of the surgical wound (total 30 mL); and in the TAP group, participants received 20 mL of bupivacaine 0.25% bilaterally in the TAP block (total 40 mL). The TAP block and wound infiltration were performed by the primary investigator and the operating obstetrician, respectively. All participants received postoperative standard analgesia (ketorolac and paracetamol) and intravenous fentanyl via patient-controlled analgesia. Patients and outcome assessors were blinded to the study group. The primary outcome was the cumulative fentanyl consumption at 24 hours. Secondary outcomes were the time to the first postoperative fentanyl dose, cumulative fentanyl consumption at 2, 4, 6, and 12 hours, pain scores at rest and on movement at 2, 4, 6, 12, and 24 hours, the deepest level of sedation, the incidence of side effects (nausea and vomiting and pruritis), and patient satisfaction. RESULTS: Data from 78 patients (39 patients in each group) were analyzed. The mean +/- SD of cumulative fentanyl consumption at 24 hours was 157.4 +/- 63.4 mu g in the infiltration group and 153.3 +/- 68.3 mu g in the TAP group (difference in means [95% confidence interval] is 4.1 [-25.6 to 33.8] mu g; P = .8). There were no significant differences between the 2 groups in the time to the first postoperative fentanyl dose, cumulative fentanyl consumption at 2, 4, 6, and 12 hours, pain scores at rest and on movement at 2, 4, 6, 12, and 24 hours, the deepest level of sedation, and patient satisfaction. The incidence of side effects (nausea and vomiting and pruritis) was low in the 2 groups. CONCLUSIONS: TAP block and wound infiltration did not significantly differ regarding postoperative fentanyl consumption, pain scores, and patient satisfaction in parturients undergoing cesarean delivery under spinal anesthesia.