The effect of traumatic brain injuries on the development of pneumonia in the critically ill patient.

Author(s):
Patrick Knight; Robert Sawyer

Background:

The potential effect of traumatic brain injury (TBI) on the microbiome of a critically ill patient is an area of study without clear results at this time. With this in mind, this study was designed to evaluate for any differences in TBI versus non-TBI trauma patients from an infectious standpoint with a focus on pneumonia.

Hypothesis:

Our hypothesis is that the TBI group would demonstrate a unique pathogen set and greater in-hospital mortality.

Methods:

Data collected prospectively on critically ill trauma patients requiring admission and treatment in an intensive care unit at a single institution from 1997 to 2017 were reviewed to identify those with ICU-acquired pneumonia based on CDC criteria. Patients were separated into two groups based on the presence of TBI defined as an acute intracranial abnormality identified on computed tomography (CT) found on admission after trauma. Continuous variables were compared using Student’s t-test and categorical variables were compared using chi-square analysis.

Results:

Among the 2723 trauma patients who developed ICU-acquired infections, 1224 developed pneumonia during their hospital course. Of these, 508 had CT evidence of an acute intracranial process, with the remaining 716 patients comprising the control group. Comparison of these groups revealed a mean APACHE II score of 17.1 ± 0.3 in the non-TBI group versus 19.6 ± 0.3 in the TBI group, p <0.0001. Crude in-hospital mortality was similar between groups: 9.1% versus 9.1%, p = 0.99.  By logistic regression analysis, in-hospital death following the diagnosis of pneumonia was associated with age and APACHE II score at the time of diagnosis, but not the presence of TBI (Odds Ratio = 0.83, 95% CI = 0.53-1.30, Hosmer-Lemeshow test p = 0.48, C statistic = 0.83). On review of the organisms isolated on culture, an increased incidence of Acinetobacter was seen in the TBI group (7.2% vs 3.2%, p < 0.05), while other pathogens were isolated at similar rates between the two groups.

Conclusions:

The presence of TBI in critical care patients with pneumonia was not shown to have an effect on the overall outcome. Although there was an increased incidence in Acinetobacter in the TBI group, the mechanism and significance of this finding is unclear and TBI does not appear to be associated with a large change in the lung microbiome.