Background
Identification of patient-specific therapy targets is crucial for traumatic brain injury (TBI) patients. The objectives were to compare the effectiveness of optimal cerebral perfusion pressure (CPPopt) targeted therapy in younger (< 45 years) and elderly (≥ 45 years) TBI patients as well as to explore the influence of various factors (cerebrovascular autoregulation (CA), cerebral perfusion pressure (CPP) declination from optimal CPP value (ΔCPPopt), age, glucose concentration in blood, etc.) on TBI patients' outcome. 

Materials and methods	
Multimodal ABP, ICP, CPP and CA monitoring of 81 TBI patients has been performed in Republic Vilnius University Hospital (Lithuania). ICM+ software (Cambridge, UK) was used for continuous CA status assessment by calculating Pressure Reactivity Index (PRx) and for identification of patient-specific CPPopt. The post-hoc analysis of associations between the patients' outcome and complex influence monitored parameters was performed by determining the most important factors affecting outcome. 

Results	
The multifactorial logistic regression model showed that the most significant factors affecting TBI patient’s outcome are age, glucose level in blood serum samples (determined within 24 h after admission), Helsinki CT (HCT) score, ΔCPPopt and duration of longest CA impairment when PRx(t)>0.5 within 24 hours after admission. The modelled accuracies for unfavorable outcome prediction were 83% and 88% respectively.  
The age>45 years was found statistically significantly associated with unfavorable outcome. OptCPP-targeted management was found statistically significantly associated with better outcome for younger patients (age<45 years). The critical values of averaged ΔCPPopt < -5 mmHg, averaged value of PRx>0.36 and duration of LCAI >100 min were found associated with mortality for younger patients group (<45 years). The critical values of averaged PRx>0.26 and duration of LCAI >61 min  were founded associated with mortality for elderly patients group (>45 years). However, no statistical differences were found between survivals and not survivals comparing ΔCPPopt for elderly patients group.

Conclusions
The main influential factors affecting severe TBI treatment outcomes are patient age, HCT, blood glucose level, and the CA status during the first day after patient admission. CPPopt-targeted patient-specific treatment is useful for stabilizing CA in severe TBI patients, as well as especially beneficial for improving outcome for younger patients less than 45-years-old. CA monitoring in first 24 hours seems to be important because especially in older patients because impaired CA is less long tolerated. However, additional research is needed to prove the applicability of CPPopt-targeted therapy for elderly patients greater than 45-years-old.

Patient-specific management of severe TBI depending on age and cerebrovascular autoregulation status