Optimizing oxygen delivery to the injured brain

The principle of optimizing oxygen delivery to the injured brain rests on the premise that both hypoxia and hyperoxia are important mediators of secondary brain injury and should be avoided. This rationale has prompted a move towards incorporating oxygenation endpoints into the management of neurocritical care patients, particularly those with traumatic brain injury. The present review will seek to describe clinical strategies to optimize oxygenation in the acutely brain-injured patient, drawing upon relevant physiologic principles and clinical data, where it exists.

A phase II randomized trial found that a protocolized approach to improving oxygen delivery resulted in less duration of brain hypoxia and a trend towards lower mortality among patients with severe traumatic brain injury. Recent clinical protocols have been published to guide oxygen delivery based on core physiologic principles: increasing oxygen supply via modulation of mean arterial pressure and intracranial pressure, blood oxygen carrying capacity, and cerebral vasoreactivity; and decreasing oxygen demand via sedation, pharmacologic coma, and hypothermia.

Although there is growing interest in the use of brain tissue oxygenation as a resuscitative endpoint, many of these therapies are based on physiologic principles with little robust clinical evidence to guide their application. Clinicians must be mindful of this and balance the putative benefits of improving oxygenation against the risks associated with the use of such therapies.