Inappropriate Prehospital Ventilation in Severe Traumatic Brain Injury Increases In-Hospital Mortality

Abstract

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 (>20 min) 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 (Pco ₂ < 35 mm Hg), normocarbic (Pco ₂ 35–45 mm Hg), and hypercarbic (Pco ₂ > 45 mm Hg). Outcome was based on mortality during hospital admission. Survival was found to be related to admission Pco ₂ 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 Pco ₂ on presentation after severe head trauma is correlated with increased in-hospital mortality. We advocate normoventilation in the prehospital setting.