No difference exists in the alteration of circadian rhythm between patients with and without intensive care unit psychosis

Objective: To determine if a difference exists in the circadian rhythm entrainment between patients with and without intensive care unit (ICU) psychosis. Design: Retrospective chart reviews from 149 consecutive patients admitted to our ICU during the period of January 1993 to August 1993. Twelve patients with a history of mental illness or alcohol or substance abuse were excluded from the study. Setting: A 20-bed surgical ICU at a large teaching hospital. Patients: Patients who remained in the ICU for a minimum of 2 days after undergoing thoracic or vascular operations. Interventions: None. Measurements and Main Results: Hourly temperature and urine output were ascertained from the patient records. The time of temperature and urine output nadir was used as a marker of circadian rhythm. Of the 137 patients included in the study, 17 (12.4%) developed ICU psychosis as defined by standard criteria. The time of temperature nadir was randomly distributed around the clock for each group. Cosinar rhythmometry analysis of temperature data showed a lack of circadian rhythm entrainment in most patients up to the third postoperative day. No statistically significant difference exists in the deviation of such impairment between the groups. Conclusion: Either patients who develop ICU psychosis have an increased sensitivity to an alteration of their circadian rhythm, or ICU psychosis develops independent of circadian rhythm abnormalities.