Major traumatic brain injury: how do hypotension and hypoxia affect mortality?

During the prehospital treatment of major traumatic brain injury, hypotension and hypoxia occur frequently. The presence of either is associated with decreased survival, but little is known about the effect on patient outcomes when they occur together. Spaite et al (2016) evaluate how hypotension and hypoxia, occurring in combination or separately, affect survival.

The authors debate what effect combining the two factors would have on mortality. Reducing oxygen delivery to neurons will have similar physiological consequences—whether the mechanism of that is hypotension or hypoxia—and some authors have suggested that their combination may add little to the risk of mortality. However, little previous evidence exists to monitor these circumstances, and even less is known about the prehospital setting. These are key reasons for evaluating the effect of blood pressure and oxygenation in the prehospital environment—particularly when the highly sensitive injured brain can be damaged even by brief periods of low oxygenation, which initiates the secondary brain injury response.