Introduction VETgirl…On-The-Run

4/23/17

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SmokeinhalationinjuryArmelledeLaforcadeDVM,DACVECC

GarretPachtinger,VMD,DACVECC

COO,VETgirl

Introduction

JustineA.Lee,DVM,DACVECC,DABTCEO,VETgirl

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ArmelleM.deLaforcade-DVM,DACVECC

AssociateProfessor,TuftsUniversity

Introduction

Introduction

• Smoke• Pathophysiology• Diagnosis• Treatment• Complications

Epidemiology

• Frequentlyaccompaniesburninjury• Increasesmortalityby20%inburnpatients• Increasesriskofpneumonia,ARDS

– Increasedmortalityto60%

Literature

• Studiesinpeople– Burnstudies,burnsepsis

• Animalmodels– Histopathology,immunechanges

• Veterinarystudies– Largelycasereports

Smokeinjury

• Directheatdamage– Upperairway,nasopharyngealmucosa

• LowFi02• Inhaledparticulates/irritants• Inhaledtoxins

• Complicatedby– Inflammatorychanges,secondarypneumonia

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Systemsaffected

• Respiratory• Centralnervoussystem

– Acute– Delayed

• Cardiovascular• Ocular• Cutaneous

Constituentsofsmoke• Whatisburning,howmuchoxygen,temperature

• Particulatematter:Soot,tar,ash,metaloxides

• Carbon: Carbonmonoxide,carbondioxide

• Nitrogen:Hydrogencyanide,ammonia,nitrogenoxides

• Halogens:hydrogenchloride,halocarbons• Fluorocarbons:hydrogenfluoride• Sulfur:hydrogensulfide,sulfurdioxide,thiols• Hydrocarbons:aldehydes

Constituentsofsmoke• Whatisburning,howmuchoxygen,temperature

• Particulatematter:Soot,tar,ash,metaloxides

• Carbon: Carbonmonoxide,carbondioxide

• Nitrogen:Hydrogencyanide,ammonia,nitrogenoxides

• Halogens:hydrogenchloride,halocarbons• Fluorocarbons:hydrogenfluoride• Sulfur:hydrogensulfide,sulfurdioxide,thiols• Hydrocarbons:aldehydes

Directthermalinjury

• Upperairway– MouthtoGlottis– Thermalinjury

• Lowerairway– Belowglottistolungparenchyma

– Chemicalinjury– Toxiccompounds

https://www.vetmed.wsu.edu

Particulatematter• Cough

– Vagalreceptorsinthroatandproximalairway– Paroxysmal/intractable

• Cellularedema,destruction– Carbonaceousaccumulation

• Reflexbronchoconstriction• Highviscositysecretions

– Lowhumidity

• Impairedmucociliaryclearance

Hypoxia

• Atelectasis• Surfactantinactivation• Obstructivecasts

– Cellulardebris,fibrinclots,leukocytes,mucus

• Pulmonaryedema– Proteinrich– Reducedcompliance,increasedresistance– Increasedworkofbreathing

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Carbonmonoxide:“thesilentkiller”

• Highlylinkedtofirerelateddeaths– Autopsystudies

• Imaging:Pulmonaryedema– Interstitial&interalveolar

• Postmortem:Pulmonaryedema&hemorrhage

COandgasexchange

• Rapidlyabsorbed• CombinationwithHb

– CO+Hbè COHb (carboxyhemoglobin)– 200-250xgreateraffinityofHb forCOthanoxygen

• Haldaneeffect– LeftshiftofoxyHb curve– Impairedoxygenrelease– Tissuehypoxia

CO:systemiceffects

• Cardiac:COaffinityformyoglobin– Myocardialdepression– Arrhythmias– Hypotension– Perpetuatestissuehypoxia

• Neurologic:demyelination– Impairedcellularuptakeofoxygen– Freeradicalformation– Coma,seizures

COtoxicity:diagnosis

• Co-oximetry– Carboxyhemoglobin levels– Heparinizedblood

• MRIlesions• Pulseoximetry

– Falselyelevated

COHb (%) Symptoms

0-5 Normal

15-20 Headache, confusion

20-40 Hallucination

40-60 Coma

60+ CPA

• 3chihuahuas,housefire• 30minutesinsmoke

• Seizures3-4daysfollowingfire– Difficulttocontrol

• Brainpathology– Neuronalnecrosis,demyelination– SupportacuteCOtoxicity

JAAHA 2010

COpoisoning:treatment

• ShortenhalflifeofCOHb– 100%oxygenadministration– Hyperbaricoxygentherapy(CoHb>25-30%)

• Slowcorrectionoflacticacidosis– Providingsomeoxygendiffusiontotissues

• Delayedeffects– Personality,behavior,memorychanges

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• 4dayspostsmokeexposure– Mentationchanges– Walkingintowalls,ataxic– Progressedtotetraparesis– Tachypnea,pneumonia

• Therapy– Antibiotics,N-acetylcysteine,supportivecare

• Followup:34months

HydrogenCyanide(CN):“thetoxictwin”

• Combustionofsynthetics– Plastics,rubber,foam,varnish,paints– Wool,silk,paper

• 1960’s-1980’s– recognizedrolesmokeinhalationinjury

• LevelsmaybebetterpredictoroflethalityinsmokeinhalationvictimsthanCO– Protocolsforprophylactictreatment

HydrogenCyanide(CN)

• Inhibitscytochromecoxidase– aerobicmitochondrialrespiration– Anaerobicrespiration

• Lacticacidosis• Cellulardamage,death

• Bindshemoglobin– Reducedoxygencarryingcapacityofblood

• Heart,brain,CNSmostaffected– Mostreliantonoxygen

CN:clinicalsigns

• CanbesimilartoCO• Firefightershavereported

– Headache,weakness,fatigue,shortnessofbreath,cough,disorientation,arrhythmias

– Heartattack

CN:clinicalsigns

• CanbesimilartoCO• Firefightershavereported

– Headache,weakness,fatigue,shortnessofbreath,cough,disorientation,arrhythmias

– heartattack

Cyanidetoxicity:diagnosis

• Oftenmissed– ‘Inlineofdutydeaths’ (LODDs)– Suddencardiacillness

• Bloodtesting:shorthalflife,sendouttest• Airmonitoring• Lactateconcentration

– IndicatoroftoxicCNlevels– Lactate>10mmolindicatesCN>39umol/L

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Cyanidetoxicity:treatment

• Hydroxocobalamin– OnlyFDAapprovedantidote– Combineswithcyanidetoformcyanocobalamin– VitaminB12precursor– Controversial

• 2017study– Safe– Reducedhospitallengthofstay,ventilatordays– Incidenceofpneumonia

ParisFireBrigade

• Criteriaforhydroxocobalaminadministration

• Extricatedfromanenclosed-spacefirescenewithsmoke

• Sootinthenose,mouth,orthroatorsootyexpectoration

• Anyalterationsinconsciousness• Hypotension

Smokeinhalation:clinicalsigns• None!• Respiratory

– Tachypnea– Cough– Harshlungsounds– Pulmonarycrackles– Nasaldischarge– Laryngeal/trachealsounds

• Mucousmembranes– Cyanosis– Hyperemic

Smokeinhalation:clinicalsigns• Neurologic

– Depressed– Ataxia– Stupor– Coma

• Dermatologic– Smokysmell– Singedhair– Burnedskin– Sootonskin

Firstassessment

• Airwaypatency– Intubateifnecessary– Lossofconsciousness

• Oxygentherapy• IVaccess

Pointofcaretesting

• Lactateconcentration• Co-oximetry

– Carboxyhemoglobinemia

• Pulseoximetry?

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Diagnostics

• Thoracicradiographs– 80%– Interstitialtoalveolar

• Bronchoscopy– Obstruction

• Arterialbloodgas– PaO2:FiO2

Diagnosticsinpeople• Bronchoscopy• Pulmonaryfunctiontesting• Pulmonaryscan

Treatment

• Oxygentherapy– Firstresponders!– Respiratoryfailure– MetabolismofCO

• Mechanicalventilation– Failuretomaintainairway– Progressiverespiratoryfailure– Unconsciousness

Hyperbaricoxygentherapy

• Deliveryofoxygenunderpressure• Oxygendiffusesintoareasoflowoxygen

– Helpischemictissues– Reducesrelianceonhemoglobin

• UsefulwithCOandCNpoisoning– DisplacesCOfromintracellularstores– Improvemitochondrialfunction

• Consideredif– Carboxyhemoglobin>25%,unconsciousness

N-acetylcysteine

• Mucolytic• People

– NebulizedN-acetylcysteine/heparin/albuterol– Attenuatelunginjury– ReduceprogressiontoARDS– Reducemortality– Somestudiesshownobenefit

• Continued5-7daysinhospital

Albuterol

• Beta-2agonist• Relaxesbronchialsmoothmusclereceptors• Reducesairwayresistance• Usefulwithseverebrochospasm

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AlphaTocopherol

• VitaminE– SuperoxideScavenger

• Smokeexposurecausesoxidativestress• VitEdepletedinburn&smokeinjury

– Sheepmodels

• Fewstudies,somesuggestimprovedgasexchangewithsupplementation

Antibiotictherapy

• Bacterialcolonizationpeaks2-3dayspostexposure

• Prophylactic:No– Promoteantibioticresistance

• Withinfection:Yes– Organismcanbedifficulttopredict– Alteredairwaymicrobiome– Broadspectrumpendingcultureresults

• Anaerobes,facultativeanaerobes

Corticosteroids

• Anti-inflammatory• MayreducepulmonaryedemaBut..• Increasedriskofpulmonaryinfection• Delayedwoundhealing• Lackofdemonstratedbenefit

• Notrecommended

Adjunctivetherapy

• Atropineophthalmic– Reduceciliaryspasm,pain

• Treatmentofburns

Complications

• ARDS– Bilateralinfiltrates Acuteonset– Severehypoxemia Absenceofheartfailure

• Pneumonia– 2-4daysafterexposure– Longtermsusceptibilitytorespiratoryinfections

• Animalmodel,people

• Sepsis– Cutaneousburns

Outcome

• 11complicated,16uncomplicated– 4died,4euthanized,3survivedintensivecare– Ifnoworseafter1day,likelyuncomplicated

• 15uncomplicated,7complicated• 20catssurvived

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Conclusion

• Smokeinhalationinjuryiscomplex• Airwaysupportiskey• Impactofdirectinjuryandtoxicgases

– Paramounttosuccessfultherapy

• Expectcomplications• Progressionofrespiratorysignsmaybeprognostic

• Greatcriticalcarecases!

Thankyou!

• armelle.delaforcade@tufts.edu

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