Effect of Preoperative Oral Melatonin on Postoperative Sedation and Analgesia among Patients Undergoing Elective Surgery under General Anaesthesia: A Randomised Controlled Study

Introduction: Postoperative pain is one of the major causes of dissatisfaction and prolonged hospital stay in patients undergoing surgery under general anaesthesia. Melatonin has been used for sleep regulation and Intensive Care Unit (ICU) sedation but there is limited knowledge regarding its effect postoperative analgesia and sedation. Aim: To evaluate the effects of preoperative melatonin on postoperative sedation and analgesia. Materials and Methods: This randomised controlled study was conducted from June 2020 to June 2021, at Mahatma Gandhi Memorial Medical College and M.Y. Hospital, Indore, Madhya Pradesh, India. Total 100 patients belonging to American Society of Anesthesiologists (ASA) grade I and II of either gender, of age 18 to 60 years who were planned for elective surgery under general anaesthesia were randomly divided into two groups. Group M (n=50) was given 6 mg oral melatonin (two capsules of 3 mg each), and group C (n=50) was given multivitamin capsules, 90 minutes before induction of anaesthesia. General anaesthesia was induced using standard method for both the groups. Sedation score was assessed in preoperative period as well as after giving drugs and till 4 hours postoperatively by using Ramsay Sedation score. Pain was evaluated by Visual Analogue Scale (VAS) score till 8 hours postoperatively. Time of request of first rescue analgesia was noted and compared to that of control group. Results: At preoperative time sedation score was comparable between both the groups. At postoperative time, sedation score 4 was seen in significantly higher number of patients of group M in comparison to group C, while at all the other time intervals, sedation scores were comparable between the two groups. Mean VAS score was found to be significantly higher in group C (3.2±0.4) in comparison to group M (3.02±0.14), 4 hours postoperatively. The mean time to request for first rescue analgesia in group M was 7.27±1.01 hours and in group C was 5.40±0.78 hour (p-value=0.001). Conclusion: Preoperative oral melatonin can be used to effectively reduce the postoperative pain without producing undue sedation.