[Perioperative melatonin circadian secretion in patients undergoing coronary artery bypass grafting surgery]

To investigate the circadian rhythm of perioperative melatonin secretion in patients undergoing coronary artery bypass grafting surgery.

Forty male patients scheduled for elective coronary artery bypass grafting surgery (CABG) under hypothermic cardiopulmonary bypass (CPB) or off-pump were allocated into two groups of 20 patients: CPB group and off-pump group. Blood samples were withdrawn from all patients immediately before the induction of anesthesia (baseline), 10 min after the induction of anesthesia, 10 min after heparinization, 30 min after commencement of CPB (or 2h after skin incision), before reversal of heparin with protamine, at the end of surgery, and. every 3 hours after operation until the twenty-fourth hour. The plasma concentration of melatonin was measured by using enzyme-linked immunosorbent assay.

The plasma melatonin concentrations during and after CPB were higher than the baseline value in the CPB group. There were no differences in the melatonin concentrations in the off-pump group. In the CPB group the melatonin concentrations after induction, during CPB, and after CPB were 7.2 +/- 3.4, 10.5 +/- 5.2, and 9.5 +/- 4.0 respectively, all significantly higher than those in the off-pump (5.5 +/- 2.5, 6.3 +/- 2.0, and 5.7 +/- 2.1 respectively, all P < 0.05). During the twenty-four hours after operation, two patients in the CPB group and six patients in the off-pump group showed circadian rhythm of melatonin secretion.

The perioperative circadian rhythm of melatonin secretion in patients undergoing CABG surgery with CPB or off-pump is disturbed, however relatively more patients under off-pump group regain secretion rhythm of melatonin in the immediate postoperative period. CPB may be one of the reasons for perioperative melatonin circadian secretion disturbance.