Disturbances in melatonin, cortisol and core body temperature rhythms after major surgery

It has been suggested that circadian rhythm disturbances are present after major surgery and that this may play a role in the development of postoperative sleep disturbances, fatigue, cognitive dysfunction and cardiovascular morbidity. The objective of this study was to examine the profile of melatonin, cortisol and core body temperature rhythms before and after major surgery.

Blood samples (melatonin and cortisol) and core body temperature readings were collected every hour in the 24-h period prior to surgery and the 48 h after surgery from 11 patients undergoing major abdominal surgery. All patients had private rooms. Light exposure was controlled and monitored. Phase markers [50% dim light melatonin onset (DLMO 50%) and offset (DLMOff 50%), cortisol and core body temperature acrophase] for the three circadian rhythm profiles were calculated before and after surgery. The correlation between the melatonin rhythm and time of surgery, duration of surgery and opioid use was examined.

A median delay in the onset of melatonin was seen on the first postoperative day [median DLMO 50% 22:46 hours (range: 21:15-01:08 hours) on the preoperative day compared with 23:54 hours (range: 19:09-02:46 hours) on the first postoperative day; P

We found disturbances in three circadian markers after major surgery. The clinical consequences of postoperative circadian disturbances should be investigated further in the future.