Continuous monitoring of the microcirculation in neurocritical care: an update on brain tissue oxygenation

Abstract

Purpose of review 

This article summarizes recent clinical and experimental studies of parenchymal brain tissue oxygen monitoring and considers future directions for its use in neurocritical care.

Recent findings 

Recent reports have focused on the relationship between brain tissue oxygen tension (P_brO₂) and other physiologic parameters such as mean arterial pressure, cerebral perfusion pressure, cerebral blood flow, and fraction of inspired oxygen. P_brO₂ appears to reflect both regional and systemic oxygen concentrations as well as microvascular perfusion through natural tissue gradients. Defining an absolute critically low P_brO₂ threshold has been challenging, but levels below 14 mmHg may have a pathophysiologic basis. Newer studies have examined dynamic changes in P_brO₂ during oxygen reactivity testing and during augmentation of cerebral perfusion pressure. P_brO₂ monitoring has now been described in a wide range of neurocritical care conditions including head trauma, subarachnoid hemorrhage, nontraumatic intracerebral hemorrhage, brain death, and brain tumor resection.

Summary 

The use of brain tissue oxygen monitoring is maturing as a tool to detect and treat secondary brain injury. P_brO₂ measurements can provide continuous quantitative data about injury pathophysiology and severity that may help optimize neurointensive care management. Prospective trials of P_brO₂ guided treatment protocols are now needed to demonstrate impact on clinical outcomes.