Critical ICP thresholds in relation to outcome: Is 22 mmHg really the answer?

Abstract

Purpose Intensive care for patients with traumatic brain injury (TBI) aims, among other tasks, at avoiding high intracranial pressure (ICP), which is perceived to worsen motor and cognitive deficits and increase mortality. International recommendations for threshold values for ICP were increased from 20 to 22 mmHg in 2016 following the findings in a study by Sorrentino et al., which were based on an observational study of patients with TBI of averaged ICP values. We aimed to reproduce their approach and validate the findings in a separate cohort. Methods Three hundred thirty-one patients with TBI were included and categorised according to survival/death and favourable/unfavourable outcome at 6 months (based on Glasgow Outcome Score—Extended of 6–8 and 1—5, respectively). Repeated chi-square tests of survival and death (or favourable and unfavourable outcome) vs. high and low ICP were conducted with discrimination between high and low ICP sets at increasing values (integers) between 10 and 35 mmHg, using the average ICP for the entire monitoring period. The ICP limit returning the highest chi-square score was assumed to be the threshold with best discriminative ability. This approach was repeated after stratification by sex, age, and initial Glasgow Coma Score (GCS). Results An ICP limit of 18 mmHg was found for both mortality and unfavourable outcome for the entire cohort. The female and the low GCS subgroups both had threshold values of 18 mmHg; for all other subgroups, the threshold varied between 16 and 30 mmHg. According to a multiple logistic regression analysis, age, initial GCS, and average ICP are independently associated with mortality and outcome. Conclusions Using identical methods and closely comparable cohorts, the critical thresholds for ICP found in the study by Sorrentino et al. could not be reproduced.

A Comprehensive Perspective on Intracranial Pressure Monitoring and Individualized Management in Neurocritical Care: Results of a Survey with Global Experts

“…For borderline ICP values like 18-22 mm Hg (and possibly lower values in selected cases) the need for additional data becomes evident, since allowing ICP to remain beyond individual safety thresholds may carry inadvertent consequences [56]. This is supported by the recent work from Riparbelli et al [4], in which a cohort of more than 300 patients found 18 mm Hg as a threshold associated with mortality and unfavorable outcomes.…”

“…Our understanding of intracranial pressure (ICP), a critical indicator of brain health, is continuously evolving [1], with satisfactory evidence supporting its monitoring as a means of outcome improvement [2,3]. However, both the safety limits and therapeutic thresholds for managing and treating ICP are still debatable [4,5], although the current recommendation is based on 22 mm Hg [6]. Several notable trials investigating traumatic brain injury (TBI), whether targeting ICP alone [7] or in combination with brain oximetry [8], employing various therapy strategies, such as decompressive craniectomy [9,10], hypothermia [11], and others, have highlighted the ongoing need for further advancement in outcome improvement.…”