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Published on: March 14, 2013
Temporal Patterns in Brain Tissue and Systemic Oxygenation Associated with Mortality After Severe Traumatic Brain
Jaskaran Rakkar1,2, Justin Azar1,2,3, Jonathan H Pelletier1,2
1Department of Critical Care Medicine, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA.
Insights
Lower brain tissue oxygen (PbtO2) and PbtO2/PaO2 ratios are linked to mortality in children with severe traumatic brain injury (TBI). These findings suggest adjusting oxygen management strategies for better outcomes in pediatric TBI patients.
Area of Science:
- Neuroscience
- Critical Care Medicine
- Pediatric Neurology
Background:
- Traumatic brain injury (TBI) poses significant risks, with brain tissue hypoxia being a key factor for poor outcomes.
- Systemic hyperoxemia, used to combat hypoxia, may also influence mortality risk in TBI patients.
- Understanding oxygen dynamics in brain tissue is crucial for managing severe TBI in children.
Purpose of the Study:
- To investigate temporal patterns of brain tissue oxygen (PbtO2), arterial oxygen (PaO2), and their ratio (PbtO2/PaO2) in relation to mortality in pediatric severe TBI.
- To identify specific oxygen thresholds associated with survival or death in this vulnerable population.
Main Methods:
- Retrospective analysis of data from 138 pediatric severe TBI patients (≤18 years) with intracranial pressure and/or PbtO2 monitoring.
- Temporal analyses of PbtO2, PaO2, and PbtO2/PaO2 were conducted for the first 5 days of hospitalization using advanced statistical models.
- Receiver operating characteristic (ROC) curves and logistic regression were used to determine mortality-associated thresholds and independent risk factors.
Main Results:
- Distinct temporal patterns of PbtO2, PaO2, and PbtO2/PaO2 were observed between survivors and nonsurvivors.
- Lower PbtO2 on days 1, 3-5, and lower PbtO2/PaO2 ratios on days 1, 2, and 5 were associated with mortality.
- Key thresholds identified: PbtO2 < 30 mm Hg and PbtO2/PaO2 ratio < 0.12 were independently linked to increased mortality risk. Hyperoxemia (PaO2 ≥ 300 mm Hg) was also a risk factor.
Conclusions:
- Impaired oxygen diffusion, indicated by lower PbtO2 and PbtO2/PaO2 ratios, is associated with mortality in pediatric severe TBI.
- Current guidelines may need revision, suggesting a higher PbtO2 threshold for optimal management.
- The PbtO2/PaO2 ratio shows promise as a valuable tool in managing severe pediatric TBI.
Background:
Brain tissue hypoxia is an independent risk factor for unfavorable outcomes in traumatic brain injury (TBI); however, systemic hyperoxemia encountered in the prevention and/or response to brain tissue hypoxia may also impact risk of mortality. We aimed to identify temporal patterns of partial pressure of oxygen in brain tissue (PbtO2), partial pressure of arterial oxygen (PaO2), and PbtO2/PaO2 ratio associated with mortality in children with severe TBI.
Methods:
Data were extracted from the electronic medical record of a quaternary care children's hospital with a level I trauma center for patients ≤ 18 years old with severe TBI and the presence of PbtO2 and/or intracranial pressure monitors. Temporal analyses were performed for the first 5 days of hospitalization by using locally estimated scatterplot smoothing for less than 1,000 observations and generalized additive models with integrated smoothness estimation for more than 1,000 observations.
Results:
A total of 138 intracranial pressure-monitored patients with TBI (median 5.0 [1.9-12.8] years; 65% boys; admission Glasgow Coma Scale score 4 [3-7]; mortality 18%), 71 with PbtO2 monitors and 67 without PbtO2 monitors were included. Distinct patterns in PbtO2, PaO2, and PbtO2/PaO2 were evident between survivors and nonsurvivors over the first 5 days of hospitalization. Time-series analyses showed lower PbtO2 values on day 1 and days 3-5 and lower PbtO2/PaO2 ratios on days 1, 2, and 5 among patients who died. Analysis of receiver operating characteristics curves using Youden's index identified a PbtO2 of 30 mm Hg and a PbtO2/PaO2 ratio of 0.12 as the cut points for discriminating between survivors and nonsurvivors. Univariate logistic regression identified PbtO2 < 30 mm Hg, hyperoxemia (PaO2 ≥ 300 mm Hg), and PbtO2/PaO2 ratio < 0.12 to be independently associated with mortality.
Conclusions:
Lower PbtO2, higher PaO2, and lower PbtO2/PaO2 ratio, consistent with impaired oxygen diffusion into brain tissue, were associated with mortality in this cohort of children with severe TBI. These results corroborate our prior work that suggests targeting a higher PbtO2 threshold than recommended in current guidelines and highlight the potential use of the PbtO2/PaO2 ratio in the management of severe pediatric TBI.
