Pre-hospital endotracheal intubation in severe traumatic brain injury: ventilation targets and mortality—a retrospective analysis of 308 patients

Background Traumatic brain injury (TBI) remains one of the main causes of mortality and long-term disability worldwide. Maintaining physiology of brain tissue to the greatest extent possible through optimal management of blood pressure, airway, ventilation, and oxygenation, improves patient outcome. We studied the quality of prehospital care in severe TBI patients by analyzing adherence to recommended target ranges for ventilation and blood pressure, prehospital time expenditure, and their effect on mortality, as well as quality of prehospital ventilation assessed by arterial partial pressure of CO 2 (PaCO 2 ) at hospital admission. Methods This is a retrospective cohort study of all TBI patients requiring tracheal intubation on scene who were transported to one of two major level 1 trauma centers in Switzerland between January 2014 and December 2019 by Swiss Air Rescue (Rega). We assessed systolic blood pressure (SBP), end-tidal partial pressure of CO 2 (PetCO 2 ), and PaCO 2 at hospital admission as well as prehospital and on-scene time. Quality markers of prehospital care (PetCO 2 , SBP, prehospital times) and prehospital ventilation (PaCO 2 ) are presented as descriptive analysis. Effect on mortality was calculated by multivariable regression analysis and a logistic general additive model. Results Of 557 patients after exclusions, 308 were analyzed. Adherence to blood pressure recommendations was 89%. According to PetCO 2, 45% were normoventilated, and 29% had a SBP ≥ 90 mm Hg and were normoventilated. Due to the poor correlation between PaCO 2 and PetCO 2 , only 33% were normocapnic at hospital admission. Normocapnia at hospital admission was strongly associated with reduced probability of mortality. Prehospital and on-scene times had no impact on mortality. Conclusions PaCO 2 at hospital admission is strongly associated with mortality risk, but normocapnia is achieved only in a minority of patients. Therefore, the time required for placement of an arterial cannula and prehospital blood gas analysis may be warranted in severe TBI patients requiring on-scene tracheal intubation.