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

Abstract

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 (PbtO₂) 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 PbtO₂ in monitoring brain oxygenation in HIBI after CA and the effect of targeted PbtO₂ 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 PbtO₂, CA, and HIBI.

Results: Among 1,077 records, 22 studies were included (16 experimental studies and six clinical studies). In experimental studies, PbtO₂ was mainly adopted to assess the impact of gas exchanges, drugs, or systemic maneuvers on brain oxygenation. In human studies, PbtO₂ was rarely used to monitor the brain oxygen tension in patients with CA and HIBI. PbtO₂ 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 PbtO₂ associated with outcome in patients with CA, as well as to understand the physiological mechanisms influencing PbtO₂ induced by gas exchanges, drug administration, and changes in body positioning after CA.

Keywords: Brain oxygen tension; Brain tissue oxygenation; Cardiac arrest; Hypoxic-ischemic brain injury; Neuromonitoring.