Failure of cerebral autoregulation and subsequent hypoperfusion is common during the acute phase of traumatic brain injury (TBI). The cerebrovascular pressure-reactivity index (PRx) indirectly reflects cerebral autoregulation and has been used to derive optimal cerebral perfusion pressure (CPP). This study provides a method for the use of a combination of PRx, CPP, and intracranial pressure (ICP) to better evaluate the extent of cerebral hypoperfusion during the first 24 hours after TBI, allowing for a more accurate prediction of mortality risk.
Continuous ICP and arterial blood pressure (ABP) signals acquired from 295 TBI patients during the first 24 hours after admission were retrospectively analyzed. The CPP at the lowest PRx was determined as the optimal CPP (CPPopt). The duration of a severe hypoperfusion event (dHP) was defined as the cumulative time that the PRx was > 0.2 and the CPP was < 70 mm Hg with the addition of intracranial hypertension (ICP > 20 or > 22 mm Hg). The outcome was determined as 6-month mortality.
The cumulative duration of PRx > 0.2 and CPP < 70 mm Hg exhibited a significant association with mortality (p < 0.001). When utilized with basic clinical information available during the first 24 hours after admission (i.e., Glasgow Coma Scale score, age, and mean ICP), a dHP > 25 minutes yielded a significant predictive capacity for mortality (p < 0.05, area under the curve [AUC] = 0.75). The parameter was particularly predictive of mortality for patients with a mean ICP > 20 or > 22 mm Hg (AUC = 0.81 and 0.87, respectively).
A short duration (25 minutes) of severe hypoperfusion, evaluated as lowered CPP during worsened cerebrovascular reactivity during the 1st day after TBI, is highly indicative of mortality.
ABBREVIATIONSABP = arterial blood pressure; AUC = area under the curve; CBF = cerebral blood flow; CPP = cerebral perfusion pressure; CPPopt = optimal CPP; ∆;CPP = optimal CPP − measured CPP; dHP = duration of a severe hypoperfusion event; dHP20 = dHP with an ICP threshold of 20 mm Hg; dHP22 = dHP with an ICP threshold of 22 mm Hg; GCS = Glasgow Coma Scale; ICP = intracranial pressure; NCCU = neurocritical care unit; PRx = pressure-reactivity index; ROC = receiver operating characteristic; TBI = traumatic brain injury.
Correspondence Dong-Joo Kim: Korea University, Seoul, South Korea. firstname.lastname@example.org.INCLUDE WHEN CITING Published online December 21, 2018; DOI: 10.3171/2018.7.JNS18995.Disclosures ICM+, a signal processing software used in this study, is licensed through Cambridge Enterprise Ltd., Cambridge, UK. M. Czosnyka has a financial interest in 10% of the licensing fee, and P. Smielewski receives part of licensing fees.
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