RESUMO
BACKGROUND: Melatonin has analgesic, anti-inflammatory, sedative, and anxiolytic properties. However, the relationship between endogenous melatonin levels and postoperative analgesic requirements has not been well elucidated in patients undergoing bariatric surgery. We studied endogenous melatonin levels, cortisol levels, body temperatures, and the relationship between the level of endogenous melatonin and postoperative morphine consumption. METHODS: The trial was conducted among 30 patients who were scheduled for laparoscopic bariatric surgery. Their ages were between 18 and 65 years and their BMIs were above 40 kg/m2. Secretion of melatonin, cortisol, and body temperature was monitored before the anesthetic induction, at 2 h intraoperatively, and at 2, 6, 10, (2:00 A.M.) and 24 h postoperatively. For each patient, morphine consumption was assessed at postoperative visits. The primary outcomes were to measure endogenous melatonin levels and to examine the relationship between these levels and morphine consumption. The secondary outcome was to observe the changes in cortisol and body temperature. RESULTS: There was a significant decrease in melatonin levels when preoperative melatonin levels were compared with intraoperative and all postoperative follow-up periods (p < 0.05). When the correlation between plasma melatonin levels and the postoperative morphine consumption of the patients was inspected, there was a significant correlation in all of the follow-up periods (p < 0.05). When preoperative cortisol levels were compared with intraoperative and postoperative cortisol levels, there was a significant difference in the follow-up periods, except two periods (p < 0.05). Body temperatures were similar in all measurement periods. CONCLUSIONS: Endogenous melatonin secretion was significantly decreased in the intraoperative and postoperative periods. Furthermore, there was a significant inverse correlation between changes in endogenous melatonin levels and morphine consumption. TRIAL REGISTRATION: Clinical Trial Number NCT03107702 from A service of the U.S. National Institutes of Health, clinicaltrials.gov.