Bilateral posterior Quadratus Lumborum block for pain relief after cesarean delivery: a randomized controlled trial

BACKGROUND: Achieving optimal analgesia with few side effects is the goal of pain management after cesarean delivery. Intrathecal (IT) morphine is the current standard but ultrasound-guided quadratus lumborum block (QLB) may offer superior pain control with fewer side effects. This study compared the pain-free period after cesarean delivery among parturients who received spinal block with IT morphine, with IT morphine and bilateral QLB, or only bilateral QLB. METHODS: Parturients having elective cesarean delivery under spinal block were randomized and allocated into IT morphine 0.2 mg with sham QLB (Group IT), IT morphine 0.2 mg and bilateral QLB with 0.25% bupivacaine 25 ml in each side (Group IT+QLB), or bilateral QLB with 0.25% bupivacaine 25 ml in each side (Group QLB). A PCA pump was connected after completion of the QLB or sham block. The first time to PCA morphine requirement was recorded and compared. RESULTS: Eighty parturients were included. Analysis of Group QLB was terminated early because at the second interim analysis, median pain-free period was significantly shorter in Group QLB [hours (95%CI): 2.50 (1.04–3.96) in Group IT vs. 7.75 (5.67–9.83) in IT+QLB vs. 1.75 (0.75–2.75) in QLB (p < 0.001)]. The median (min, max) amount of morphine required during 24 h was 5.5 (0–25) in Group IT vs. 5.0 (0–36) in IT+QLB vs. 17.5 (1–40) mg in Group QLB (p < 0.001). In the final analysis the median pain-free period was 2.50 (1.23–3.77) hours (95%CI) in Group IT (n = 27) vs. 8.02 (5.96–10.07) in IT+QLB (n = 28). (p = 0.027). CONCLUSION: US-QLB used in conjunction with IT morphine yielded a statistically significant longer median pain-free period compared with standard IT morphine alone. However, QLB alone provided inferior pain control compared with standard IT morphine. When combined with IT morphine, QLB could provide additional analgesic benefit as a part of multimodal analgesic regimen, especially during the early postoperative period. TRIAL REGISTRATION: ClinicalTrials.gov no. NCT03199170 Date registered on June 22, 2017. Prospectively registered.