Investigation of melatonin, corti̇zol, changes in body temperature and the relationship between melatoni̇n level and analgesia requerment undergoing bariatric surgery

Objective Major surgical operations are characterized by endocrine-metabolic and surgical stress response during postoperative period. Pain, fatigue, sleep, general condition and cognitive dysfunction are common after major surgery. It is suggested that sleep and circadian rhythm disturbance may be had an influence on postoperative morbidity. Melatonin, which has anxiolytic, sedative, and analgesic effects, plays an important role in regulation of endocrine rythm. Cortisol also plays an important role in the survival of the organism when a stress response occurs. In this prospective observational study; we aimed to evaluate the endogenous melatonin levels, cortisol levels and body temperature, and to investigate the relationship between melatonin level and postoperative morphine consumption in laparoscopic bariatric surgery patients. Materials and Methods A total of 34 patients, between the age of 18-65, ASA I-II, obesity, body mass index over 40 kg /m2, scheduled for laparoscopic bariatric surgery were enrolled into study. Patients were taken into operating room without any premedication. General anesthesia was induced with 2-3 mg / kg propofol, 1 μg / kg fentanyl, and 0.6 mg / kg rocuronium for muscle relaxation. Anesthesia was maintained with 1 MAK sevofluran and mixure of 40% O2- 60% air. BIS value was kept between 40-60. Five ml blood sample were taken preoperatively, intraoperatively at 2 hours, postoperatively at 2, 6, 10, 24 hours and at 02:00 postoperatively to assess melatonin and cortisol levels. Body temperatures were also recorded during these monitoring periods. One g iv acetaminophen (Perfalgan® 1 g / 100 mL vial) was infused slowly in 30 minutes, at the end of the operation before wound closure and in every 6 hours until 24 hours postoperatively for postoperative pain management. Also, PCA using 10 mL of morphine sulfate (100 mg) plus 90 mL of SF (1 mg bolus with a 15min lockout), was set up for postoperative 24 h. Morphine consumption at postoperative 2, 6, 10, 24 hours and at 02:00 were recorded. Results The demographic data of the patients were similar. The mean preoperative plasma melatonin level was 78.96 ± 39.82 pg/mL. We found that melatonin secretion maintained circadian rhythm in the 24-hour period and that the highest melatonin level (39.09  31.02) was at 02:00 in this period. There was a significant decrease in melatonin levels at all measurement times compared to the preoperative levels. Significant correlations were observed between plasma melatonin levels and postoperative morphine consumption values in all follow-up periods. The mean preoperative plasma cortisol level was 15.78 6.70 /dl. We found that cortisol secretion maintained circadian rhythm in the 24-hour period and that the lowest cortisol level (9.82  6.29) was at 02:00 in this period. According to preoperative values, we found an increase at intraoperatively and until postoperative 6 hours. Compared with preoperative values, there was a significant difference in follow-up periods except postoperative 6th and postoperative 24th hours. The body temperatures of the cases were similar in all measurement periods. Conclusion In conclusion, in this prospective observational study in obese patients undergoing laparoscopic bariatric surgery, melatonin showed diurnal rhythm but reduced melatonin levels were observed in intraoperative and postoperative period compared to preoperative value. A statistically significant relationship was found between the decrease in melatonin level and increase in consumption of morphine. Cortisol was also present in the diurnal rhythm, level increased till 6 hours postoperatively, decreased after 6 hours and reduced the lowest value at 02:00 and reached the almost baseline level at 24 hours postoperatively.