The burden of traumatic brain injury (TBI) is enormous, affecting an estimated 69 million individuals throughout the world each year, with an estimated 11% of those sustaining severe TBI [1]. Annually in the United States, TBI leads to 2.2 million emergency department (ED) visits, 280,000 hospitalizations, 52,000 deaths, and over $60 billion in economic costs [2,3]. While improving outcomes has been difficult [4], early management may help mitigate secondary brain injury [[4], [5], [6], [7], [8]] and this has led to the promulgation of evidence based TBI guidelines for prehospital care [[5], [6], [7],9,10]. Prior to the recently reported results of the Excellence in Prehospital Injury Care (EPIC) study, no large, controlled evaluation of the guidelines had been published. EPIC demonstrated that implementation of the EMS guidelines was associated with significant improvement in adjusted odds of survival to hospital discharge among patients with severe TBI [11,12]. A primary component of these guidelines is the immediate prevention and treatment of hypotension.

Hypotension in the setting of TBI causes secondary brain injury and has been associated with poorer outcomes when occurring during the prehospital and early trauma center care [11,[13], [14], [15], [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], [26], [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], [37], [38], [39], [40], [41]]. Recent research has also established the dose-dependent effects of hypotension on TBI mortality [42]. Little is known about the association between prehospital hypotension and hypotension occurring during initial resuscitation at the trauma center. We are unaware of any reports assessing the relative impact on outcome when hypotension occurs in the field versus after trauma center arrival.