OBJECTIVETo investigate perioperative patterns of melatonin and cortisol secretion rhyme in patients undergoing coronary artery bypass grafting surgery.

METHODSEleven male patients scheduled for elective coronary artery bypass grafting surgery (CABG) under hypothermic cardiopulmonary bypass (CPB) were enrolled in the study. Anesthesia was induced and maintained with propofol (3 mg.kg-1.h-1) and supplemented with fentanyl (15 micrograms/kg). Blood samples were taken during surgery at specific time-points and every 3 h in the immediate postoperative period and postoperative day 2 and day 3. Plasma melatonin and cortisol levels were measured by radioimmunoassay and enzyme-linked immunosorbent assay respectively.

RESULTSDuring surgery, plasma melatonin levels were below the minimum sensitivity level but low levels, without circadian variation, were measured during the immediate postoperative period. During postoperative day 2 and day 3, circadian secretion patterns of melatonin were present in 10 patients and showed an inverse correlation with light intensity exposed (r = -0.480, P = 0.01). Plasma cortisol levels in the immediate postoperative period were significantly higher than those before induction of anesthesia (P < 0.01). During postoperative day 2 and day 3, only 3 patients regained circadian secretion of cortisol.

CONCLUSIONSIt is concluded that melatonin and cortisol secretion are disrupted during cardiac surgery and in the immediate postoperative period.