Correlation between serum melatonin circadian rhythm and intensive care unit psychosis after thoracic esophagectomy.

BACKGROUND: Intensive care unit (ICU) psychosis is still a relatively frequent complication after esophageal surgery. We investigated the correlation between ICU psychosis and serum melatonin concentration during the period after esophagectomy. METHODS: The study group comprised 41 patients who underwent esophagectomy for treatment of esophageal cancer between 1999 and 2001. The cohort included 36 men and 5 women, aged 36 to 78 years. After surgery, blood samples were collected 4 times a day for 4 days. Serum levels of melatonin were determined with a melatonin radioimmunoassay kit. The regularity of the melatonin circadian rhythm pattern, as defined by the frequency of occurrence of the peak level of melatonin secretion, was determined (the pattern was described as irregular at less than 3 times in the measurement period). RESULTS: Of the 41 patients who met the inclusion criteria, 11 (26.8%) had ICU psychosis develop. These patients were older than those patients in whom ICU psychosis did not develop (P =.01). No significant differences were seen in the duration of surgery, volume of blood loss, term in the ICU, term of intubation, tumor location, disturbances of organ function, and postoperative complications between patients in whom ICU psychosis developed, and those patients in whom it did not. Patients with ICU psychosis tended to have abnormally low serum levels of melatonin. Of the 41 patients studied, 9 (22%) had an irregular pattern of melatonin circadian rhythm. A significant correlation was seen between ICU psychosis and an irregular melatonin circadian rhythm (P =.0001). CONCLUSION: Irregular patterns of melatonin circadian rhythm may be associated with ICU psychosis. Supplementation with melatonin, or acceleration of melatonin secretion, may protect patients from development of ICU psychosis and may promote recovery to a normal mental state.