Impact of Bilateral Transmuscular Quadratus Lumborum Block Using Different Doses of Dexmedetomidine as an Adjuvant Combined with Ropivacaine for Postoperative Analgesia in Laparoscopic Myomectomy

Introduction The optimal dosage of dexmedetomidine (DEX) as an adjuvant combined with ropivacaine for postoperative analgesia in laparoscopic myomectomy is still controversial. The main aim of this prospective clinical trial was to evaluate the analgesic effect and relevant adverse effects of different doses of dexmedetomidine applied locally for ropivacaine-induced bilateral transmuscular quadratus lumborum block (TQLB). Methods TQLB was conducted using different doses of dexmedetomidine per side (R group: control group; DEX1 group: 0.1μg/kg; DEX2 group: 0.3μg/kg; DEX3 group: 0.5μg/kg). Numeric rating scales (NRS) of pain score, heart rate (HR) and blood pressure (BP) were assessed at different time points after performing TQLB. Dosage of additional analgesics via patient-controlled analgesia pump, recovery time for anal exsufflation, hospital stay and clinical events such as nausea, vomiting and pruritus were also compared among groups. Results A total of 200 patients underwent laparoscopic myomectomy were enrolled in this study and divided into 4 groups (R, DEX1, DEX2 and DEX3 group) randomly, 50 for each group. Compared with R group, NRS pain score was significantly lower in DEX2 group and DEX3group (p<0.001) 10 minutes after TQLB. Twenty minutes after TQLB, statistical significance of NRS pain score appeared between DEX1 group and R group (p<0.05) and between DEX2, 3 group and DEX1 group (p<0.001). In comparison to R group and DEX1 group, NRS pain score in DEX2 and DEX3 group were lower within 24 hours postoperatively (p<0.05). HR in DEX2 group and DEX3 group was significantly lower than DEX1 group and R group (p<0.05). 2 patients in DEX2 and DEX3 group were developed severe low HR of which HR was below 50bpm. Even 6 hours after surgery, patients in DEX3 group still remained severe low HR. Patients in DEX2 group and DEX3 group needed fewer PCA bolus deliveries than patients in R group and DEX1 group (p<0.001). Satisfaction score of postoperative analgesia was higher in DEX2 group and DEX3 group in comparison to DEX1 group and R group (p<0.001).group and DEX3 group in comparison to DEX1 group and R group (p<0.001). Conclusion 0.3μg/kg per side of dexmedetomidine as an adjuvant for TQLB was recommended to effectively relieve postoperative pain after laparoscopic myomectomy. Trial registration Chinese Clinical Trial Registry with registration number ChiCTR1900028509. Date of registration: 24 November 2019. http://www.chictr.org.cn/edit.aspx?pid=42635=htm=4