Effect of Two Doses of Oral Melatonin on Perioperative Anxiety and Postoperative Analgesia in Patients Undergoing Orthopaedic Surgeries: A Randomised Controlled Study

Introduction: Perioperative anxiety and postoperative pain are the most common complaints associated with orthopaedic surgeries leading to increased morbidity and hospital stay. Melatonin, a recent alternative to benzodiazepines with fewer side-effects, has been shown to reduce anxiety and pain in perioperative settings. Aim: To investigate the anxiolytic effect of melatonin perioperatively and its analgesic potency postoperatively. Materials and Methods: The present randomised, controlled double-blinded study was conducted including 90 patients equally distributed to three groups receiving placebo (Group P), 6 mg (M6) and 12 mg oral melatonin (M12) 60-90 minutes before surgery. Primary outcome was preoperative anxiety, assessed using State Trait Anxiety Inventory (STAI) before drug administration and 60-90 minutes after it. Postoperative anxiety, assessed using STAI and and postoperative pain, assessed using Visual Analogue Score (VAS) for the next 72 hours both at rest and in movement, time of request for rescue analgesia and total analgesic requirements within 72 hours were considered as secondary outcomes. One-way Analysis of Variance (ANOVA) and Kruskal-Wallis test were used to compare the three groups regarding continuous and dichotomous variables, respectively. Results: Ninety patients were enrolled in the study and were randomly distributed into three matched groups according to age, sex, anthropometric parameters and American Society of Anaesthesiologists (ASA) grading. Significantly reduced (p<0.001) STAI scoring was found in group M12, from the preoperative period to 72 hours postoperatively. A statistically significant reduction in VAS scoring for pain both at rest and movement was always observed in group M12 from six hours to 72 hours postoperatively (p<0.001). The time of request for first and second rescue analgesics in group M12 was significantly later than group M6 and group P. Total consumption of rescue analgesics was found to be significantly low (p<0.001) in group M12. Conclusion: A 12 mg of oral melatonin premedication reduces anxiety during perioperative phase as compared to 6 mg of melatonin and placebo, with no significant difference between the latter two. It was also found that significant reduction in postoperative anxiety and pain at rest and during movement in the M12 group, but not in groups M6 and P. M12 group also required significantly less rescue analgesic than groups M6 and P. In summary, 12 mg of oral melatonin exhibited desired analgesic, sedative and anxiolytic properties to ameliorate perierioperative anxiety and postoperative pain, without any negative haemodynamic effect.