Low brain tissue oxygenation contributes to the development of delirium in critically ill patients: A prospective observational study

Abstract

Purpose: To test the hypothesis that poor brain tissue oxygenation (BtO₂) during the first 24h of critical illness correlates with the proportion of time spent delirious. We also sought to define the physiological determinants of BtO₂.

Materials and methods: Adult patients admitted to the ICU within the previous 24h were considered eligible for enrollment if they required mechanical ventilation, and/or vasopressor support. BtO₂ was measured using near-infrared spectroscopy, for 24h after enrollment. Hourly vital signs and clinically ordered arterial and central venous blood gases were collected throughout BtO₂ monitoring. Patients were screened daily for delirium with the confusion assessment method for the intensive care unit (CAM-ICU).

Results: BtO₂ and the proportion of time spent delirious did not result in a significant correlation (p=0.168). However, critically ill patients who spent the majority of their ICU stay delirious had significantly lower mean BtO₂ compared to non-delirious patients, (p=0.017). BtO₂ correlated positively with central venous pO₂ (p=0.00003) and hemoglobin concentration (p=0.001). Logistic regression indicated that lower BtO₂, higher narcotic doses and a history of alcohol abuse were independent risk factors for delirium.

Conclusions: Poor cerebral oxygenation during the first 24 hours of critical illness contributes to the development of delirium.

Trial registration: This trial is registered on clinicaltrials.gov (Identifier: NCT02344043), retrospectively registered January 8, 2015.

Keywords: Brain tissue oxygenation; CAM-ICU; Cerebral perfusion; Critical illness; Delirium; Near-infrared spectroscopy.