Methods of monitoring brain oxygenation

Abstract

Posttraumatic brain ischemia or hypoxia is a major potential cause of secondary injury that may lead to poor outcome. Avoidance, or amelioration, of this secondary injury depends on early diagnosis and intervention before permanent injury occurs. However, tools to monitor brain oxygenation continuously in the neuro-intensive care unit have been lacking. In recent times, methods of monitoring aspects of brain oxygenation continuously by the bedside have been evaluated in several experimental and clinical series and are potentially changing the way we manage head-injured patients. These monitors have the potential to alert the clinician to possible secondary injury and enable intervention, help interpret pathophysiological changes (e.g., hyperemia causing raised intracranial pressure), monitor interventions (e.g., hyperventilation for increased intracranial pressure), and prognosticate. This review focuses on jugular venous saturation, brain tissue oxygen tension, and near-infrared spectroscopy as practical methods that may have an important role in managing patients with brain injury, with a particular focus on the available evidence in children. However, to use these monitors effectively and to understand the studies in which these monitors are employed, it is important for the clinician to appreciate the technical characteristics of each monitor, as well as respective strengths and limitations of each. It is equally important that the clinician understands relevant aspects of brain oxygen physiology and head trauma pathophysiology to enable correct interpretation of the monitored data and therefore to direct an appropriate therapeutic response that is likely to benefit, not harm, the patient.