Multimodal Neuromonitoring in Acute Brain Injury

Substudy 1: This study investigates the relationship between glucose in blood and microdialysate (MD-glucose) in patients with severe traumatic brain injury (TBI) or aneurysmal subarachnoid haemorrhage (SAH). Substudy 2: The aim of this substudy is to examine the contribution of arterial oxygen tension (PaO2) to PbtO2 in patients with acute brain injury. We hypothesize that there is an association between the two parameters, that this relationship is altered in patients with concurrent intracranial hypoertension, and that a higher burden of cerebral hypoxia is associated with poor functional outcome and mortality. Substudy 3: The study aims to estimate the contribution of systemic lactate to microdialysate lactate, hypothesizing that: 1. PbtO2 and cerebral perfusion pressure are independent predictors of microdialysate lactate in patients with cerebral hypoxia (PbtO2\<20). 2. Systemic lactate is an independent predictor of microdialysis lactate in patients without cerebral hypoxia. Substudy 4: The study aims to establish whether there is a predictive threshold value of MD-glutamate for unfavourable functional outcome 6 months after ictus of brain injury. Additionally, we aim to explore whether there is a pattern of MD-glutamate that can predict episodes of neuroworsening.