Monitoring of Brain Tissue Oxygen Tension in Cardiac Arrest: a Translational Systematic Review from Experimental to Clinical Evidence.

Background: Cardiac arrest (CA) is a sudden event that is often characterized by hypoxic-ischemic brain injury (HIBI), leading to significant mortality and long-term disability. Brain tissue oxygenation (PbtO) is an invasive tool for monitoring brain oxygen tension, but it is not routinely used in patients with CA because of the invasiveness and the absence of high-quality data on its effect on outcome. We conducted a systematic review of experimental and clinical evidence to understand the role of PbtO in monitoring brain oxygenation in HIBI after CA and the effect of targeted PbtO therapy on outcomes.

Methods: The search was conducted using four search engines (PubMed, Scopus, Embase, and Cochrane), using the Boolean operator to combine mesh terms such as PbtO, CA, and HIBI.

Results: Among 1,077 records, 22 studies were included (16 experimental studies and six clinical studies). In experimental studies, PbtO was mainly adopted to assess the impact of gas exchanges, drugs, or systemic maneuvers on brain oxygenation. In human studies, PbtO was rarely used to monitor the brain oxygen tension in patients with CA and HIBI. PbtO values had no clear association with patients' outcomes, but in the experimental studies, brain tissue hypoxia was associated with increased inflammation and neuronal damage.

Conclusions: Further studies are needed to validate the effect and the threshold of PbtO associated with outcome in patients with CA, as well as to understand the physiological mechanisms influencing PbtO induced by gas exchanges, drug administration, and changes in body positioning after CA.