The Effect of the Magnesium Sulfate in Ultrasound-Guided Quadratus Lumborum Block on Postoperative Analgesia: A Randomized Controlled Trial.

Abstract

Quadratus lumborum block (QLB) has proven to be an effective analgesic technique in various abdominal surgeries. Magnesium sulfate as an adjuvant in different nerve blocks has been reported. The aim of this study was to assess the efficacy of magnesium sulfate as an adjuvant to ropivacaine in an ultrasound-guided QLB for postoperative analgesia in laparoscopic gynecologic surgery. Ninety patients belonging to American Society of Anesthesiologists (ASA) physical statusI or II, aged between 40 and 60years, scheduled for laparoscopic gynecologic surgery were enrolled. Patients were divided into three groups and received bilateral quadratus lumborum block: ropivacaine group (groupN, 0.375% ropivacaine 40ml + normal saline 4ml), magnesium sulfate group (groupM, 0.375% ropivacaine 40ml + 10% magnesium sulfate 4ml), and control group (groupC, normal saline 44ml). Visual analogue scale (VAS) at rest and during activity at 4, 6, 12, 24, and 48h postoperatively, consumption of morphine, the time of first analgesic request, frequency of rescue analgesia, satisfaction with postoperative analgesia, and any side effects were recorded. VAS scores in groupsM and N were significantly lower than in groupC at 4 and 6h postoperatively (P < 0.001). VAS scores were lower in groupM at 12 and 24h postoperatively compared to groupsN and C (P < 0.05). The mean total morphine consumption was significantly lower in groupM than in groupsN and C (P < 0.001). The mean time to the first patient-controlled analgesia (PCA) bolus was significantly prolonged in groupM compared to groupC (P < 0.05). The satisfaction with postoperative analgesia of groupM was superior to that of groupsN and C (P < 0.05). There was no significant difference in side effects among the three groups. Magnesium sulfate as an adjuvant to ropivacaine in ultrasound-guided QLB prolongs the duration of analgesia, decreases analgesic requirements, and improves patient satisfaction without significant side effects. Chinese Clinical Trial Registry, ChiCTR1900027066.