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 LiteratureAppendixTable 2. Studies of altitude-related brain damageAuthor(s), Journal Title Population (N) FindingsFayed et al. (2006)Am J Med, 119,168.e1-168.e6Jersey (2010) AviatSpace EnvironMed, 82, 64-68Paola et al. (2008)European JNeurology, 15,1050-1057Evidence of braindamage after highaltitudeclimbing bymeans of magneticresonance imagingSevere neurologicaldecompression sicknessin a U-2 pilotReduced oxygen due tohigh-altitude exposurerelates to atrophy inmotor function brainareasCivilianN=35 climbers (12professional, 23 amateur)N=20 controlsCase report (N=1)CivilianN=9 world-class climbersN=19 non-exposed controlsMRI evidence of irreversible lesions(frontal, parietal) in amateurs and diffusecortical atrophy in professionals afterclimbing to 4810-8848 meters w/osupplementary oxygen.Pilot who experienced DCS at very highaltitude (cabin pressure 8500 meters).Examination revealed bilateral frontal andright cerebellar evidence of hypoxia andischemia, as well as persistent cognitiveimpairments and balance deficits.Climbers showed subtle white and greymatter MRI abnormalities in brain motorcortices after climbing to > 7500 metersw/o supplementary oxygen. Repeatedextreme altitude exposure was associatedwith changes in left primary andsupplemental motor cortices (right handcontrol). Single exposure was associatedwith changes in left angular gyrus (motorplanning).Table 3. Studies of aeromedical transport of TBIAuthor(s),Journal Title Population (N)Davis et al.(2005)Annals ofEmergencyMedicine, 46,115-122Donovan etal. (2008)Aviat SpaceEnviron Med,79, 30-35The impact ofaeromedicalresponse topatients withmoderate to severetraumatic braininjuryAeromedicalevacuation ofpatients withpneumocephalus:outcomes in 21casesCivilianN = 10,314 totalN = 3,017 local Aeromedtransport by helicoptermoderate & severe TBImean GCS = 9.5MilitaryN=21 head injuries +intracranial air (N=19post-craniotomy)Long-range air transportin pressurized aircraftTBI severity not specifiedOutcome xTBI severityStatisticallysignificantbenefit ofairtransportfor severeTBI patients(GCS < 9)NRFindingsRetrospective study of outcomes foraeromedical vs. ground transport ofmoderate and severe TBI patients.Transport altitude not specified.Outcomes were significantly betteroverall for aeromedically transportedTBI patients. Greatest benefitobserved for more severe TBIs (meanGCS = 4.1). Survival improved forpatients intubated during air transportvs. ground transported patientsintubated in emergency department.Retrospective study of outcomesamong 21 head injury patients withintracranial air (mean volume 9.3 ml)who underwent long-range airevacuation in pressurized equivalent5000-8000 feet. No patients showedclinical neurological deterioration intransport or within 24 hours of arrival.September 14, 2010 38
Traumatic Brain Injury (TBI) and Effects of Altitude:An Analysis of the LiteratureTable 4. Studies of hypoxia effects on TBI outcomeAuthor(s),Journal Title Population (N)Ariza et al.(2004)J Neurotrauma,21, 864-876Chang et al.(2009) Crit CareMed, 37, 283-290Chi et al. (2006)J Trauma, 61,1134-1141Davis et al.(2009) JNeurotrauma,26, 2217-2223Jiang et al.(2002)J Neurotrauma,19, 869-874Manley et al.(2001) ArchSurg, 136, 1118-1123Influence ofextraneurologicalinsults on ventricularenlargement andneuropsychologicalfunctioning aftermoderate and severetraumatic brain injuryPhysiologic andfunctional outcomecorrelates of braintissue hypoxia intraumatic brain injuryPrehospital hypoxiaaffects outcome inpatients withtraumatic brain injury:a prospectivemulticenter studyBoth hypoxemia andextreme hyperoxemiamay be detrimental inpatients with severetraumatic brain injuryEarly indicators ofprognosis in 846 casesof severe traumaticbrain injuryHypotension, hypoxia,and head injury:frequency, duration,and consequencesCivilianN=57Moderate TBI(N=18)Severe TBI (N=39)CivilianN=27Severe TBIGCS < 7CivilianN=150Moderate & severeTBIGCS < 13CivilianN = 3420Moderate tosevere TBIMean GCS = 11.6CivilianN = 864Severe TBIGCS < 9CivilianN = 107Moderate tosevere TBIGCS < 13Outcome xTBI severityEffects ofhypoxiawereindependentof TBIseverityN/ANRNRN/ANo effect ofhypoxiaFindingsRegardless of TBI severity, episodes ofhypoxia (and hypotension) were relatedto neuropsychological outcome andlong-term ventricular enlargement. Prehospitalhypoxia was related to thirdventricle dilatation and neurological andcognitive impairments of attention,motor speed, mental flexibility, fluency,and verbal memory.Retrospective review of severe TBIpatients in an intensive care unit. Braintissue oxygen levels were monitoredand measured hourly. Hypoxic episodeswere common, usually associated withnormal ICP. Frequency and duration ofbrain tissue hypoxia were related topoor functional outcome.Prospective study found that withmultiple other variables controlled,hypoxia in the prehospital setting wasassociated with significantly highermortality after brain injury. Mortalityfor patients with hypoxic episodes was37% (vs. 20%); of the 43 (29%) patientswho had hypoxic episodes, 36% died.Patients with prehospital episodes ofhypoxia (and/or hypotension) requiredlonger hospital stays and had a greaterdegree of disability at discharge.Retrospective analysis found that bothhypoxemia and extreme hyperoxemiawere related to a decrease in goodoutcome and increase in mortality formoderate-to-severe TBI patients.Authors concluded that there may be atherapeutic range for oxygen, withoptimal PO2 range 110-487 mmHg.Retrospective study of 864 severe TBIpatients found that in addition to age,GCS, and pupillary response/size, thepresence of hyperthermia, hypoxia, andhigh ICP were also strongly correlatedwith patient outcome.Prospective study reported nosignificant effect of hypoxia during earlyresuscitation in the emergencydepartment. Authors noted lack ofhypoxia effect may have been due torecording artifacts.September 14, 2010 39
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