The effect of melatonin on prevention of postoperative delirium after lower limb fracture surgery in elderly patients: a randomized double blind clinical trial

Background: Postoperative delirium is a common complication with a high morbidity rate. This study was designed to consider the effectiveness of melatonin in prevention and treatment of postoperative delirium. Methods: Seventy-two patients aged > 60 years old with Abbreviated Mental Test (AMT) > 8 scheduled for orthopedic surgery under spinal anesthesia, were randomly distributed equally to melatonin or placebo groups. In the melatonin group, the patients were given 5 mg melatonin capsules orally the night before surgery, the night of the operation, and two nights after the surgical operation at 9 pm. Likewise, in the placebo group, the patients received placebo in the same times. For diagnosis of postoperative delirium, the AMT test was used before the operation and three days after that. The Generalized estimating equations model (GEE) with logit link to Multivariate analysis was used in the study and P < 0.05 was considered statistically significant. Results: In total, 72 patients completed the study. Thirty-three patients (45.8%) were male with a mean (SD) age 71.4 (3.6) years. On the first day after the surgery, the incidence of delirium was significantly lower in the melatonin group compared to the placebo group (22.2% vs. 44.4%, P=0.046). On the second and third days after the surgery, the level of delirium in the melatonin group was also significantly lower than that in the placebo one. The GEE model showed a significant interaction between time and treatment groups. Conclusion: The findings of the study showed that melatonin prevented delirium after the orthopedic surgeries in the elderly patients and could be useful for the patients as such.