The effect of addition of different doses of ondansetron tolidocaine as a component of intravenous regional anesthesia: a randomized double-blinded controlled study

Background The aim of this study was to evaluate and compare the analgesic effect of adding two different doses (4or 8 mg) of ondansetron to lidocaine for intravenous regional anesthesia (IVRA). Patients and methods Ninety-nine patients were randomly assigned into three groups. IVRA was achieved with lidocaine 3 mg/kg 0.5% (C group) (n = 33), lidocaine 3 mg/kg 0.5% plus 4 mg ondansetron (O1 group) (n = 33) or lidocaine 3 mg/kg 0.5% plus 8 mg ondansetron (O2 group) (n = 33). Times of onset and offset of sensory and motor blockade and the time of tourniquet pain were recorded. Postoperative visual analogue scale, time to first dose, and total amount of supplementary analgesia (diclofenac) were recorded. Results Significantly shorter onset times and longer recovery times of sensory and motor block were recorded in groups O1 and O2 compared with group C (P 0.05) with no significant difference between groups O1 and O2. Delayed onset of tourniquet pain occurred in groups O1 and O2 compared with group C (P 0.05) with a significant difference between groups O1 and O2. Eighteen patients required intraoperative fentanyl to control tourniquet pain in group C compared with 10 patients in group O1 and three patients in group O2, respectively. A significantly lower postoperative visual analogue scale score, a longer time to first dose and lower consumption of diclofenac were recorded in groups O1 and O2 compared with group C with a significant difference between groups O1 and O2. No adverse effects were noted in any patients. Conclusion Addition of ondansetron to lidocaine enhanced the performance of lidocaine when used in IVRA, prolonged postoperative analgesia and reduced intraoperative and postoperative analgesia. However, adding 8 mg ondansetron to lidocaine provided better analgesia than 4 mg.