The Role of Brain Tissue Oxygenation Monitoring in the Management of Subarachnoid Hemorrhage: A Scoping Review.

Monitoring of brain tissue oxygenation (PbtO) is an important component of multimodal monitoring in traumatic brain injury. Over recent years, use of PbtO monitoring has also increased in patients with poor-grade subarachnoid hemorrhage (SAH), particularly in those with delayed cerebral ischemia. The aim of this scoping review was to summarize the current state of the art regarding the use of this invasive neuromonitoring tool in patients with SAH. Our results showed that PbtO monitoring is a safe and reliable method to assess regional cerebral tissue oxygenation and that PbtO represents the oxygen available in the brain interstitial space for aerobic energy production (i.e., the product of cerebral blood flow and the arterio-venous oxygen tension difference). The PbtO probe should be placed in the area at risk of ischemia (i.e., in the vascular territory in which cerebral vasospasm is expected to occur). The most widely used PbtO threshold to define brain tissue hypoxia and initiate specific treatment is between 15 and 20 mm Hg. PbtO values can help identify the need for or the effects of various therapies, such as hyperventilation, hyperoxia, induced hypothermia, induced hypertension, red blood cell transfusion, osmotic therapy, and decompressive craniectomy. Finally, a low PbtO value is associated with a worse prognosis, and an increase of the PbtO value in response to treatment is a marker of good outcome.