The effectiveness of the intramuscular quadratus lumborum block in postoperative analgesia after cesarean section with vertical incision: a randomized, double-blinded placebo-controlled study

Purpose Quadratus lumborum block (QLB) has recently been used for postoperative analgesia after abdominal surgery. Although there are several approaches to QLB, the effectiveness of intramuscular QLB (QLBi) remains controversial. The aim of the present study was to examine the effectiveness of QLBi for postoperative analgesia after cesarean section with a vertical midline incision. Methods In this single-center, randomized, double-blinded placebo-controlled study, 36 women who were scheduled for elective cesarean section were randomly divided into a QLBi group ( n = 18) and a placebo group ( n = 18). In both groups, spinal anesthesia was performed with 10–11 mg hyperbaric bupivacaine and 15 µg fentanyl. After the surgery, in the QLBi group, 0.4 mL/kg of 0.25% ropivacaine was injected into the bilateral quadratus lumborum muscle under ultrasound guidance (the total volume was 0.8 mL/kg). In the placebo group, instead of ropivacaine, the subjects were injected with the same amount of normal saline. The primary outcome measure was elapsed time to first analgesic use from the QLBi block after cesarean section. Results The data from all 36 patients were analyzed. There were no significant differences between the QLBi and placebo groups regarding elapsed time to first postoperative analgesic use [mean 230 (standard deviation 103) vs 194 (89) min; 95% confidence interval − 101 to 30; p = 0.27]. Conclusions QLBi with the concentration and amount of local anesthetic used in the present study was clinically slightly effective, and the effect was limited for postoperative analgesia after cesarean section.