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.