General anesthesia for surgery influences melatonin and cortisol levels

The purpose of this study was to investigate the effect of general anesthesia and surgery on melatonin production, and to assess the relationship between melatonin secretion and cortisol levels. Twenty (9 males and 11 females) consecutive otherwise healthy patients aged 27 to 52 years were included in this study. The patients underwent laparoscopic cholecystectomy or laparoscopic hernioplasty. All patients had general anesthesia with the same anesthetic drugs. Serum cortisol levels were measured at several time periods. Urine collections for melatonin were performed from 18:00 to 7:00 the day prior to surgery, on the operation day, and on the first postoperative day. Baseline melatonin metabolites were measured the night prior to surgery, and the level was found to be 1979 +/- 1.76 ng. The value decreased to 1802 +/- 1.82 ng (NS) on the night of surgery, and it became a significantly higher, reaching 2981 +/- 1.55 ng the night after surgery (p =.003). The baseline daytime cortisol level was significantly lower than the baseline night cortisol level (6.87 +/- 1.51 mu g/dI, 14.89 +/- 1.66 micrograms/dl, respectively, p < 0.0001). Surgery induced a significant increase in both day and night cortisol levels. Daytime cortisol levels increased from 6.89 +/- 1.51 mu g/dl to 16.90 +/- 1.27 mu g/dl (p < 0.0001), whereas right levels increased from 14.89 +/- 1.66 mu g/dl to 29.20 +/- 1.24 mu g/ dl (p < 0.0001). The morning after surgery, cortisol levels decreased to 10.16 +/- 1.40 mu g/dl, lower than the value obtained on the day of surgery (p < 0.0001). As was true of melatonin, cortisol levels did not reach the pre operative level (p < 0.005). The finding of the current study is that melatonin and cortisol levels show an inverse correlation after surgery.