Artikel
Cerebral Physiology after Traumatic Brain Injury: Entropy of Monitoring Indices
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Veröffentlicht: | 9. Juni 2017 |
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Objective: Depleted entropy of mean intracranial pressure (ICP), measured by a grading tool titled “complexity index” (CI), calculated with multiscale entropy analysis, correlates with worse outcome after traumatic brain injury (TBI). We went on to study whether entropy of indices, describing ICP fluctuations, cerebral perfusion pressure (CPP), cerebral compensatory reserve, and cerebral autoregulation (CA) correlates with outcome ?
Methods: We analyzed continuous high resolution recordings from the Addenbrooke’s Hospital, Cambridge, UK, TBI-single center database in 313 patients. Arterial blood pressure (ABP) and ICP recordings were converted to 60-second averages of (a) ICP pulse amplitude (AMP); (b) cerebral perfusion pressure (CPP); (c) RAP, an index of cerebral compensatory reserve, measured as a correlation coefficient (R) between ICP amplitude (A) and mean ICP pressure (P); and (d) PRx, an index of cerebral autoregulation, measured as a moving correlation coefficient between MAP and ICP. These time series were subjected to multiscale entropy analysis, resulting in complexity indices: CI-AMP, CI-CPP; CI-RAP, and CI-PRx calculated as the sum of the first 20 scales of entropy. CIs were then compared to outcome at 6 months post injury, measured by the 5-point Glasgow Outcome Scale (GOS 1-good; GOS 5-dead).
Results: There was a 24% mortality in our series with a 43% favorable outcome (good & moderate recovery). Twenty-two patients (7%) had an average ICP>25mmHg. Both CI-AMP and CI-CPP decreased with worsening outcome (R= -0.18, p= 0.0018; and R= -0.16, p=0.0058, resp.). CI-RAP increased with worsening outcome (R=0.15, p=0.01). The CI-PRx outcome correlation was not significant. CI-RAP and CI-AMP were useful for distinction between favorable and unfavorable outcome (Kruskal Wallis test: p=00002, and p=0.001, resp.), while CI-PRx and CI-CPP were not. AMP, but not RAP was significantly higher in patients with ICP>25mmHg (p=0.023 vs. p=0.78, resp.)
Conclusion: Entropy of secondary cerebral monitoring parameters varies. Preservation of the complexity of ICP amplitude fluctuations and CPP entropy are positive prognostic TBI markers. Entropy of cerebral compensatory reserve, however, is a negative prognostic marker. Entropy of CA is unrelated to outcome. Further studies should investigate if these findings may yield early monitoring signs of deterioration for individual patients, which may lead to targeted therapy adjustments, and eventually better outcomes.