Optimal volume of ropivacaine solution for bilateral quadratus lumborum block to provide postoperative analgesia after cesarean section: a prospective, randomized, cohort study

BACKGROUND: Despite the introduction of modern postoperative pain management techniques, pain after cesarean section remains a relevant issue in obstetric anesthesiology, as it increases the risk of postoperative complications. The use of regional analgesia techniques as a central component of multimodal pain management reduces adverse drug reactions and serves as an effective option, particularly following cesarean section. AIM: The work aimed to improve the effectiveness of early postoperative analgesia in parturients after cesarean section by assessing the impact of local anesthetic volume in bilateral type 3 quadratus lumborum block. METHODS: A prospective, single-center, randomized, cohort study was conducted, involving 94 women who received postoperative analgesia via type 3 quadratus lumborum block with ropivacaine at a total dose of 180 mg. The patients were randomized into three groups: group A (n = 31) to receive 30 mL of anesthetic dilution; group B (n = 30), 40 mL; and group C (n = 32), 20 mL. The quality and duration of analgesia, as well as the area of sensory block, were assessed during the study. Cold sensation testing and the visual analog scale were used for evaluation. Assessment was performed both at rest and during movement. The need for additional analgesia was also assessed. RESULTS: In most patients in group C (n = 20, 60%), the area of analgesia was limited to the ThXI–ThXII levels, whereas in group B, more than half (n = 18, 56%) reported analgesia at all targeted levels. Group A demonstrated results that were intermediate between the two extremes. These results indicate a correlation between the extent of the block and the administered volume of local anesthetic. The quality of analgesia was higher in the groups receiving larger volumes of local anesthetic compared with those receiving smaller volumes. The differences in analgesia quality among the study groups were statistically significant. CONCLUSION: The comparative study of three volumes of a standard dose of ropivacaine for postoperative analgesia using quadratus lumborum block in parturients showed the highest efficacy with a dilution volume of 40 mL, indicating that the volume of solution affects the quality of analgesia.