Inappropriate prehospital ventilation in severe traumatic brain injury increases in-hospital mortality

In the setting of acute brainstem herniation in traumatic brain injury (TBI), the use of hyperventilation to reduce intracranial pressure may be life-saving. However, undue use of hyperventilation is thought to increase the incidence of secondary brain injury through direct reduction of cerebral blood flow. This is a retrospective review determining the effect of prehospital hyperventilation on in-hospital mortality following severe TBI. All trauma patients admitted directly to a single level 1 trauma center from January 2000 to January 2007 with an initial Glasgow Coma Scale (GCS) score ≤8 were included in the study (n=77). Patients without documented or with late (>20min) arterial blood gas at presentation (n=12) were excluded from the study. The remaining population (n=65) was sorted into three groups based on the initial partial pressure of carbon dioxide: hypocarbic (Pco₂<35mm Hg), normocarbic (Pco₂ 35-45mm Hg), and hypercarbic (Pco ₂>45mm Hg). Outcome was based on mortality during hospital admission. Survival was found to be related to admission Pco₂ in head trauma patients requiring intubation (p=0.045). Patients with normocarbia on presenting arterial blood gas testing had in-hospital mortality of 15%, significantly improved over patients presenting with hypocarbia (in-hospital mortality 77%) or hypercarbia (in-hospital mortality 61%). Although there are many reports of the negative impact of prophylactic hyperventilation following severe TBI, this modality is frequently utilized in the prehospital setting. Our results suggest that abnormal Pco₂ on presentation after severe head trauma is correlated with increased in-hospital mortality. We advocate normoventilation in the prehospital setting.