Abstract
Background
Analysis of intracranial multimodality monitoring data is challenging, and quantitative methods may help identify unique physiological signatures that inform therapeutic strategies and outcome prediction. The aim of this study was to test the hypothesis that data-driven approaches can identify distinct physiological states from intracranial multimodality monitoring data.
Methods
This was a single-center retrospective observational study of patients with either severe traumatic brain injury or high-grade subarachnoid hemorrhage who underwent invasive multimodality neuromonitoring. We used hierarchical cluster analysis to group hourly values for heart rate, mean arterial pressure, intracranial pressure, brain tissue oxygen, and cerebral microdialysis across all included patients into distinct groups. Average values for measured physiological variables were compared across the identified clusters, and physiological profiles from identified clusters were mapped onto physiological states known to occur after acute brain injury. The distribution of clusters was compared between patients with favorable outcome (discharged to home or acute rehab) and unfavorable outcome (in-hospital death or discharged to chronic nursing facility).
Results
A total of 1704 observations from 20 patients were included. Even though the difference in mean values for measured variables between patients with favorable and unfavorable outcome were small, we identified four distinct clusters within our data: (1) events with low brain tissue oxygen and high lactate-to-pyruvate ratio–values (consistent with cerebral ischemia), (2) events with higher intracranial pressure values without evidence for ischemia (3) events which appeared to be physiologically “normal,” and (4) events with high cerebral lactate without brain hypoxia (consistent with cerebral hyperglycolysis). Patients with a favorable outcome had a greater proportion of cluster 3 (normal) events, whereas patients with an unfavorable outcome had a greater proportion of cluster 1 (ischemia) and cluster 4 (hyperglycolysis) events (p < 0.0001, Fisher–Freeman–Halton test).
Conclusions
A data-driven approach can identify distinct groupings from invasive multimodality neuromonitoring data that may have implications for therapeutic strategies and outcome predictions. These groupings could be used as classifiers to train machine learning models that can aid in the treatment of patients with acute brain injury. Further work is needed to replicate the findings of this exploratory study in larger data sets.
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Funding
This work received National Institutes of Health (Grant Nos. 1R01NS082309-01A1, NS082309, NS060653).
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Dr. R and Dr. B developed the presented idea. Dr. R extracted and organized the data. Dr. B the analysis. Dr. WB, Dr. EM-G and Dr. K verified the analytical methods and provided guidance regarding analyses. Dr. R and Dr. B wrote the article in consultation with Dr. WB, Dr. EM-G and Dr. K. All authors approve of the final manuscript.
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Dr. Rajagopalan has nothing to disclose. Wesley Baker has nothing to disclose. Dr. Elizabeth Mahanna-Gabrielli has nothing to disclose. Dr. Andrew Kofke and Dr. Ramani Balu have received funding from the National Institutes of Health (NS082309 and NS060653, respectively).
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Ethical guidelines were adhered to. The Institutional Review Board of the University of Pennsylvania approved the current retrospective study and waived the need for obtaining informed consent from the patient cohort.
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Rajagopalan, S., Baker, W., Mahanna-Gabrielli, E. et al. Hierarchical Cluster Analysis Identifies Distinct Physiological States After Acute Brain Injury. Neurocrit Care 36, 630–639 (2022). https://doi.org/10.1007/s12028-021-01362-6
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DOI: https://doi.org/10.1007/s12028-021-01362-6