Background: Transversus abdominis plane (TAP) block provides 12-24 h of analgesia to the parietal peritoneum and abdominal wall, and are best used combined with oral or intravenous medications. Despite ease of use, a large margin of safety, and a high success rate, TAP blocks remain under used in settings where patients could most benefit from their use. Previous studies have used oral or intravenous narcotics for supplementation. However, the efficacy of TAP blocks in low-resourced settings where patients do not have dependable access to these medications is unknown. This study examines TAP block analgesic efficacy after caesarean section in a poorly resourced setting. We compared the post-operative status of 170 women with self-administered paracetamol-diclofenac with or without TAP blocks. We hypothesised that the block would decrease pain at 8 h, 16 h, and 24 h at rest, with coughing and upon standing.
Methods: Between Oct 31, and Dec 28, 2013, 180 women were enrolled and randomly assigned to receive either TAP or sham blocks after caesarean section. Bi-institutional (Mbarara Regional Referral Hospital and Massachusetts General Hospital) institutional review board approval was obtained for this single-centre study. After informed written consent, patients received TAP or sham blocks after caesarian section. Inclusion criteria for enrolment were: age 18 years or older, weight at least 50 kg, no allergies to study medications, otherwise healthy (American Society of Anesthesiologists classification status I or II), and having undergone elective, urgent, or emergent caesarian section under spinal anaesthesia without sedation. Under ultrasound guidance, 20-25 mL of 0·25% bupivacaine (epinephrine 1:400 000) were injected near the triangles-of-Petit. Sham blocks consisted of a transducer with a needleless syringe pressed over each flank. In the post-anaesthesia recovery area, all patients received 1000 mg paracetamol and 50 mg diclofenac, orally, to be continued on an 8-h schedule for 3 days. A skilled (masked) research nurse collected all data. The primary outcomes measured were numerical rating scale at 8 h, 16 h, and 24 h at rest, with coughing, and upon standing. The association between the pain scores at each time and type of treatment (TAP vs sham blocks) was assessed using general linear model with repeated measures. Demographics were compared using the two sample t-test (appendix).
Findings: 170 patients completed the study; 86 in the sham group and 84 in the study group. Demographics (age, weight, and parity) were similar between both study groups. One participant from the sham group was missing parity information (appendix). Preliminary data analysis showed reduced pain scores at all times, and with all degrees of movement for the TAP group (appendix). The largest reduction in pain was at 8 h (resting 33%, coughing 36%, and standing 44%). With time, the pain scores of the TAP group changed a little, whereas a decreasing trend can be noted in the sham group. No adverse events occurred.
Interpretation: This study show a significant improvement in pain scores for obstetric patients receiving a transversus abdominis plane block in comparison to standard of care in a low income, limited resource setting. The use of these blocks shows the use of an easy, inexpensive, and achievable pain control option. Especially in resource-limited areas, this approach could allow for better pain management and a new standard of care for the world's most common operative procedure.
Funding: Eleanor and Miles Harvard Medical School Shore Fellowship Grant, and Massachusetts General Hospital, DACCPM Faculty Development Grant.
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