Traumatic Brain Injury and Effects of Altitude - Human Performance ...

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Traumatic Brain Injury (TBI) and Effects of Altitude:An Analysis of the Literatureespecially in the context of aeromedical evacuation that may require rapid ascent in unpressurizedaircraft. Clinical research to date emphasizes the need for efficient medical evacuation as well as earlymitigation of hypoxia, hypotension, ICP, dehydration and uncontrolled temperature abnormalities.Specifically, our review and analysis finds that:Exposure to very high altitudes can induce brain damage and impair cognitive functioning.Hypoxia, which is correlated with poor TBI outcome, likely plays a major role in altitude-relatedbrain injury.Elevated ICP and hypotension play an important role in determining outcome from brain injury.Fluid resuscitation and management is important to prevent hypotension and prevent adverseeffects of secondary brain injury and/or altitude exposure.Hyperthermia is a risk factor for secondary brain injury. Hyperthermia is common in post-acuteTBI, and can be the result of environmental high temperatures, strenuous physical activity,infection, or injury-related hypothalamic damage and impaired thermoregulation.Hypothermia has been linked to increased mortality in general trauma patients, including thosewith TBI. Hypothermia is a concern in military operational settings and in military aeromedicalevacuation, where the average interior temperature of a military cargo plane is around 59 °F.To reduce the risks associated with hyperthermia and hypothermia, it is important to assess andstabilize temperature in the pre-hospital setting.Retrospective clinical studies suggest that preventing hypoxia, controlling high ICP and temperaturestabilization are beneficial to TBI patient outcome. Therefore, it is important that TBI patients avoidexposure to hypoxia, hypotension, and extreme temperatures in the immediate aftermath of injury.Through this analysis, several key knowledge gaps are apparent. Primarily, there is a pressing need forclinical studies and/or case reports of military aeromedical evacuation and transport involving TBIcasualties. Virtually no research has yet been published to address the unique injury and treatmentexperiences of military TBI casualties in high-altitude settings. Clinical findings are crucial to inform thedevelopment of risk and injury profiles and protocols which can address timing and interventionsneeded to prevent adverse outcomes from exposure to altitude-related factors, as well as secondarybrain injury events. Specifically, additional research is needed to address the following concerns:Identify risks, benefits, intervention strategies and outcomes associated with militaryaeromedical transport of TBI casualtiesThis information is needed to identify the “ideal time to fly” and to inform risk profiles andinjury protocols to address the timing and use of interventions to mitigate adverse effects ofaltitude and/or secondary brain injury events.Document the effects of altitude exposure on mild TBI (mTBI) and blast-induced neurotrauma(BINT)Although mTBI can involve structural neurological damage, little if any research to date hasaddressed the potential impact of secondary brain injury processes on mTBI. Most military TBIsare classified as mild, related to the effects of blast or explosion. The potential impact of altitudeon these injuries is largely unknown.September 14, 2010 2
Traumatic Brain Injury (TBI) and Effects of Altitude:An Analysis of the LiteratureDetermine what, if any, health risks or performance effects might occur among post-TBI/postconcussionmilitary personnel who return to duty at high altitudesOperational performance at altitude introduces physiologic stress, which may reveal lingeringfunctional post-TBI or repeated concussion-related deficits otherwise not clinically apparent atsea level. It is essential to determine how the return to duty in high-altitude and mountainousterrain might affect the health or performance of military personnel who are classified asrecovered from TBI.Investigate the efficacy of pharmacotherapeutic interventions for the prevention of altituderelatedand secondary brain injuriesMedications effective in treating altitude illness can improve oxygenation and reduceinflammatory responses. To the extent that these processes also mediate secondary braininjury, altitude medications may be useful to mitigate effects of altitude and secondary injury onTBI outcome. Conversely, it is important to identify medications that are contraindicated for usein TBI at altitude.TBI is a persistent challenge in civilian and military settings, due to the inherent difficulties of preventingsecondary brain injury and controlling for environmental factors that may provoke or aggravatesecondary injury. Practical challenges are most pronounced in the combat casualty environment, wheremilitary medical practitioners are expected to deliver care in austere and sometimes hostileenvironments. This review hopes to inform these efforts, and to catalyze additional research as neededto determine optimal solution sets and treatment strategies.September 14, 2010 3
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