Rationale: Traumatic hemorrhage remains the leading cause of potentially survivable deaths in Warfighters. Current clinical practice guidelines (CPGs) for the pre-hospital treatment of casualties without direct evidence of traumatic brain injury emphasize the use of permissively hypotensive resuscitation until definitive care is achieved at a Role 3 facility. Acute implementation of this strategy within the golden hour improved outcomes in recent conflicts that occurred in areas capable of timely evacuation. With tension mounting in Pacific regions, reality dictates that if conflicts emerged in locations such as Asia, geographic restrictions will extend medical evacuation to a Role 3 facility by up to 72 hours from time of injury. Our current understanding of the clinical implications of prolonged field care (PFC) following current CPGs is undefined. Therefore, it is of upmost importance to preclinically investigate the clinical implications and limitations of PFC permissive hypotensive resuscitation and, additionally, identify the physiologic parameter(s) that are most ideal for determination of patient status and guiding resuscitation.

Objectives: The overall objectives of the proposed study are: (1) define the limitations of hypotensive resuscitation in the setting of PFC; (2) characterize the pathophysiology of prolonged hypotension or hypotensive resuscitation; and (3) improve understanding of physiologic parameters requiring monitoring and intervention in order to reduce morbidity and mortality during PFC. The specific aims of this study have been carefully designed to ensure an improved understanding of the clinical implications and limitations of PFC and provide a fair, meaningful evaluation of advanced physiologic monitoring modalities to serve as superior detectors of physiologic derangements that associate with poor clinical outcomes.

Focus Areas: This study is directly in line with multiple focus areas and specific efforts specified in the Prolonged Field Care Research Award. By determining the duration of hypotensive resuscitation that is truly permissible with optimal outcomes following definitive care and full resuscitation, we are addressing Focus Area 1, with the specific goal of characterizing and mitigating the pathophysiology of prolonged hypotension or hypotensive resuscitation. Additionally, by incorporating multiple advanced physiologic monitoring modalities, we are addressing Focus Area 2, with the specific goal of improve understanding of physiologic parameters requiring monitoring and intervention in order to reduce morbidity and mortality during PFC.

Clinical Applications: The need to utilize PFC is foreseeable in both military and civilian sectors. While future military conflicts are expected to occur in locations necessitating PFC, civilian casualties occurring in secluded and remote locations will also require PFC. Developing an understanding of the clinical implications of PFC is a real-world issue that has the potential to affect every trauma patient. In pursuit of defining the clinical implications of PFC, we aim to identify physiologic parameter(s) that may serve as early warning signs of impending poor outcomes. The current clinical practice to determine patient status and guide resuscitation is based on systemic hemodynamics (e.g., systolic blood pressure and heart rate). The validity of this practice has been consistently challenged as our understanding of shock pathology suggests that observable derangements in systemic hemodynamic parameters typically occur late into the progression of shock, which greatly narrows the optimal window for successful resuscitation. For these studies, we will comprehensively evaluate several advanced physiologic monitoring devices to determine systemic and cerebral hemodynamics and oxygenation. Importantly, it should be noted that the devices to be evaluated are commercially available and Food and Drug Administration-approved for clinical application. If successful, this study will support improvements to CPGs by defining the limitations of the current standard of care hypotensive resuscitative strategy and provide a more detailed understanding of the physiologic derangements that require prompt attention to optimize outcomes following definitive care and full resuscitation.