Simulated aeromedical evacuation exacerbates burn induced lung injury:targeting mitochondrial DNA for reversal

Background:Aeromedical evacuation of patients with burn trauma is an important transport method in times of peace and war,during which patients are exposed to prolonged periods of hypobaric hypoxia;however,the effects of such exposure on burn injuries,particularly on burn-induced lung injuries,are largely unexplored.This study aimed to determine the effects of hypobaric hypoxia on burn-induced lung injuries and to investigate the underlying mechanism using a rat burn model.Methods:A total of 40 male Wistar rats were randomly divided into four groups(10 in each group):sham burn(SB)group,burn in normoxia condition(BN)group,burn in hypoxia condition(BH)group,and burn in hypoxia condition with treatment intervention(BHD)group.Rats with 30%total body surface area burns were exposed to hypobaric hypoxia(2000 m altitude simulation)or normoxia conditions for 4 h.Deoxyribonuclease I(DNase I)was administered systemically as a treatment intervention.Systemic inflammatory mediator and mitochondrial deoxyribonucleic acid(mtDNA)levels were determined.A histopathological evaluation was performed and the acute lung injury(ALI)score was determined.Malonaldehyde(MDA)content,myeloperoxidase(MPO)activity,and the nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3(NLRP3)inflammasome level were determined in lung tissues.Data among groups were compared using analysis of variance followed by Tukey’s test post hoc analysis.Results:Burns resulted in a remarkably higher level of systemic inflammatory cytokines and mtDNA release,which was further heightened by hypobaric hypoxia exposure(P<0.01).Moreover,hypobaric hypoxia exposure gave rise to increased NLRP3 inflammasome expression,MDA content,and MPO activity in the lung(P<0.05 or P<0.01).Burn-induced lung injuries were exacerbated,as shown by the histopathological evaluation and ALI score(P<0.01).Administration of DNase I markedly reduced mtDNA release and systemic inflammatory cytokine production.Furthermore,the NLRP3 inflammasome level in lung tissues was decreased and burn-induced lung injury was ameliorated(P<0.01).Conclusions:Our results suggested that simulated aeromedical evacuation further increased burn-induced mtDNA release and exacerbated burn-induced inflammation and lung injury.DNase I reduced the release of mtDNA,limited mtDNA-induced systemic inflammation,and ameliorated burn-induced ALI.The intervening mtDNA level is thus a potential target to protect from burn-induced lung injury during aeromedical conditions and provides safer air evacuations for severely burned patients.

Aeromedical evacuation of injured hikers inHong Kong

BACKGROUND： Hiking is a very popular sport in Hong Kong. Serious injuries can sometimes occur in the remote areas not accessible to roads. Aeromedical evacuation service is run by the Government Flying Service （GFS） with emergency physicians and nurses as volunteers in Hong Kong. In this paper we describe the pro？ le and outcome of injured hikers rescued by the GFS.METHODS： In this retrospective review, nature of the complaints, medical team composition, vital signs, clinical assessment and diagnosis on site were collected from the GFS medical record. Demographic data, final diagnoses and outcomes of the patients were retrieved from emergency department （ED） and hospital discharge records.RESULTS： A total of 275 cases were recruited for the 3-year period from January 2003 to December 2005. The mean age of the group was 39 years （range 1-83） with more males （159, 58%） than females. Heat illnesses, injuries and medical problems each constituted about one third of the cases. Lower limb injuries accounted for nearly half of the injuries. About 30% of the rescued hikers did not register to be seen at the ED. Only 48 hikers （17.5%） required admission and four were admitted to intensive/coronary care units for heat stroke and acute coronary syndrome. Five cases of pre-hospital cardiac arrest were recorded.CONCLUSION： Most hikers evacuated by the GFS did not suffer from serious conditions. GFS should still be prepared for the occasional cases that require advanced life support.