Does hypoxia affect intensive care unit delirium or long-term cognitive impairment after multiple trauma without intracranial hemorrhage?

BACKGROUND: Within the traumatic brain injury population, outcomes are affected by hypoxic events in the early injury period. Previous work shows a high prevalence of cognitive deficits in patients with multiple injuries who do not have intracranial hemorrhage identified on admission head computed tomography scan. We hypothesize that intensive care unit (ICU) delirium and long-term cognitive impairment (LTCI) are more likely in patients who have a hypoxic event within the first 48 hours of ICU admission.
METHODS: A total of 173 patients with multiple injuries (Injury Severity Score [ISS] >15) who presented to a Level I trauma center from July 2006 to July 2007 were enrolled in a study on long-term cognitive deficit. Ninety-seven patients required ICU management and all had continuous oxygen saturation data collected. The Confusion Assessment Method for the ICU was collected twice a day on all patients in ICU. Of the total enrolled population, 108 (62%) were evaluated 12 months after discharge by neuropsychological tests. Cognitive impairment was defined as having 2 neuropsychological test scores, 1.5 standard deviations below the mean or 1 neuropsychological test score, and 2 standard deviations below the mean. Demographic data, ISS, initial 24-hour blood requirements, presence of hypoxia (SpO(2) <90% and <85%) or hypotension (systolic blood pressure <90 mm Hg), emergency department (ED) pulse, Glasgow Coma Scale score, ventilator and ICU days were recorded. Significant univariate identification of clinical variables was used for multivariate analysis.
RESULTS: Fifty-five of 97 ICU patients (57%) were Confusion Assessment Method-ICU positive for delirium and 59 of 108 (55%) demonstrated cognitive impairment at 12-month follow-up. There was no significant association between hypoxia and ICU delirium (74.5% vs. 74%; p = 0.9) or LTCI (89% vs. 83%; p = 0.5). Ventilator days (8.7 ± 8.9 vs. 2.9 ± 4.6; p < 0.0001), ED pulse (109 ± 28.5 vs. 94 ± 22.8; p = 0.01), and blood transfusions (10 U ± 10.8 U vs. 5 U ± 5.3 U; p = 0.015) were significant independent predictors of delirium. Ventilator days (odds ratio, 1.16; 95% confidence interval, 1.05-1.29; p = 0.004) and ED pulse (odds ratio, 1.02; 95% confidence interval, 1.00-1.04; p = 0.03) remained significant predictors of ICU delirium after adjusting for ISS, hypoxic state, blood transfusions, and ED blood pressure. Among ED Glasgow Coma Scale score (10.5 ± 5.1 vs. 11.4 ±5.5; p = 0.7), ISS (33.3 ± 10.1 vs. 32.2 ± 9.0; p = 0.5), ventilator days (6.5 ± 7.5 vs. 6.2 ± 8.8; p = 0.4), blood transfusions (8.1 ± 6.8 vs. 9.4 ± 8.1; p = 0.4), and delirium (62% vs. 62.5%; p = 0.9), there were no significant univariate associations with LTCI.
CONCLUSIONS: Hypoxic events in the ICU do not have a direct correlation with ICU delirium or LTCI in the patients with multiple injuries without evidence of intracranial hemorrhage.