STARSHIP Part 2: Disturbed Pressure Reactivity Duration and Magnitude in Pediatric Severe Traumatic Brain Injury-Outcome Implications

Abstract

Cerebral autoregulation (CA) plays a critical role in maintaining cerebral blood flow (CBF) amid fluctuations in systemic blood pressure, with dysfunction increasing vulnerability to secondary brain injury, particularly after traumatic brain injury (TBI). While extensively studied in adults, CA dynamics in pediatric TBI (pTBI) remain relatively unexplored. Studying Trends in AutoRegulation in Severe Head Injury in Pediatrics (STARSHIP), the first multicenter, prospective study on CA in pTBI, investigates the pressure reactivity index (PRx) and its association with outcomes. PRx, calculated as the Pearson's correlation between mean arterial pressure and intracranial pressure, provides insights into the patient's CA status. In this article, STARSHIP Part 2 characterizes PRx disturbances using dose metrics that take the magnitude of PRx disturbance, and the time in which the patient experiences this derangement, into consideration. We calculated the dose (overall and hourly) and percentage time spent with a PRx above thresholds 0-0.4 in 135 children with TBI. Associations with outcome were explored via summary metrics and over time, using uni- and multivariable, and ordinal regression with propensity score matching, correcting for known outcome predictors. Patients with poor outcomes exhibited higher PRx dose and percentage time above threshold, even after adjusting for clinical predictors. Time trend analyses highlighted elevated PRx metrics in poor outcome groups during the first-week post-injury. Duration of impaired pressure reactivity, as denoted by the percentage time a patient spent with a PRx >0, is robustly and independently associated with dichotomized outcome at 12 months post-ictus. Our results highlight the predictive strength of PRx metrics, with percentage time above a threshold of 0 emerging as the most robust indicator of 12-month outcome. This work supports further investigation into the feasibility and impact of interventions guided by real-time CA monitoring in severe pTBI.

Keywords: cerebral autoregulation; multimodality monitoring; pediatric traumatic brain injury; pressure reactivity index.

FIG. 1.

The dose concept. Patients 1 and 2 have the same overall mean PRx of 0.196. However, as demonstrated, Patient 2 experiences notable periods of PRx >0.3 (orange dotted line used as reference for threshold). Hence, exploring the dose of PRx above threshold can be a more valuable metric to describe the patient’s cerebrovascular pressure reactivity in continuous monitoring than summary metrics. The overall and hourly dose metrics differ as the hourly dose accounts for any gaps of monitoring data. PRx, pressure reactivity index; AUC, area under the curve; Ptime, percentage monitoring time.

FIG. 2.

Metrics for PRx >0.4 and PRx >0 over time for mortality and outcome groups, respectively, where the overall (A and B) and hourly (C and D) dose of PRx above threshold is shown, as well as the percentage monitoring time (Ptime) of the patients spent with a PRx above threshold (E and F). Yellow and blue bars show results for nonsurvivors and survivors, respectively (A, C, E), while red and purple bars represent unfavorable and favorable outcome groups (B, D, F). Day 0 represents the day of ictus. PRx, pressure reactivity index; Ptime, percentage monitoring time (%).

FIG. 3.

Correlations between PRx variables and clinical metrics. Spearman’s correlation was used, with correlation coefficients shown as values, where the shading color represents the strength and direction of correlation, with purple indicating a positive correlation and pink a negative correlation. AIS, Abbreviated Injury Scale; GCS, Glasgow Coma Scale; ISS, Injury Severity Scale; PRx, pressure reactivity index; Ptime, percentage monitoring time.