Secondary brain insults after head injury: clinical perspectives

Secondary brain insults, particularly hypotension (systolic blood pressure < 95 mm Hg) and hypoxia (PaO2 < 60 torr), are the most powerful determinants of outcome from severe head injury (SHI) that are amenable to therapeutic manipulation. Well over one quarter of SHI patients appear to suffer one or more secondary insults during the time between injury and resuscitation. Furthermore, although improved strategies for airway management have decreased the incidence of preresuscitation hypoxia, little progress has been made in ameliorating the influence of hypotension during this period. The incidence of hypotension in the ICU is also > 25%, and such episodes also appear to be significant predictors of poor outcome independent of their etiologies and of preresuscitation secondary insults. In all, over one third of all SHI patients appear to experience one or more secondary insults during their acute post-injury course, and these events are correlated with a doubling of mortality and a large increase in morbidity. The approach to proper management of such secondary brain insults requires only an increased recognition of their importance, greater vigilance toward monitoring, and improved application of therapeutic maneuvers that are generally already available. Given their prevalence and impact on outcome, prevention/correction of secondary brain insults may be the most powerful means of improving outcome from severe brain injury available today.