$Objectives:$ In severe traumatic brain injury (TBI), cerebral perfusion pressure (CPP) management based on cerebrovascular pressure reactivity (PRx) has the potential to provide a personalised treatment target to improve patient outcomes. So far, the methods have focused on identifying one autoregulation guided CPP target – called CPPopt. We investigated whether a CPP autoregulation range - which uses a continuous estimation of the ‘lower’ and ‘upper’ CPP limits of cerebrovascular pressure autoregulation (PRx) - has prognostic value.

$Design:$ Single-centre retrospective analysis of prospectively collected data

$Setting:$ The neurocritical care unit at a tertiary academic medical centre

$Patients:$ Data from 729 severe TBI patients admitted between 1996 and 2016 were used. Treatment was guided by controlling intracranial pressure and CPP according to a local protocol.

$Interventions:$ None

$Methods\; and\; Main\; Results:$ CPP-PRx curves were fitted automatically using a previously published curve-fitting heuristic from the relationship between PRx and CPP. The CPP values at which this ‘U-shaped curve’ crossed the fixed threshold from intact to impaired pressure reactivity (PRx =0.3) were denoted automatically the ‘Lower’ and ‘Upper’ CPP Limits of Reactivity (LLR and ULR), respectively. The % of time with CPP below (%CPP<LLR), above (%CPP>ULR) or within these reactivity limits (%CPP WLR) was calculated for each patient and compared across dichotomised Glasgow Outcome Scores. After adjusting for age, initial GCS, and mean ICP, %CPP<LLR was associated with unfavourable outcome (OR %CPP<LLR 1.04, 95%-CI 1.02-1.06, p <0.001) and mortality (OR 1.06 95%-CI 1.04-1.08, p<0.001).

$Conclusions:$ Individualised autoregulation-guided CPP management may be a plausible alternative to fixed CPP threshold management in severe TBI patients. Prospective randomized research will help to define which autoregulation guided method is beneficial, safe and most practical.