Hypothermia, Prevention, Recognition, Treatment_ Hypothermia Special Situations

8/10/2019 Hypothermia, Prevention, Recognition, Treatment_ Hypothermia Special Situations

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HypothermiaSpecialSituations

ThispaperisprovidedherewithpermissionfromAndrewDWeinberg,MD

hypothermia;pathophystology;resuscitation;rewarming;treatmentalgorithm

FromHarvardMedicalSchool.Boston,Massachusetts.and

Brockton/WestRoxburyVAMC,WestRoxbury,Massachusetts.

AndrewDWeinberg,MD

Significanthypothermiaisanincreasingclinicalproblemthatrequiresarapidresponsewithproperlytrainedpersonnelandtechniques.Althoughtheclinicalpresentationmaybesuchthatthevictimappearsdead,aggressivemanagementmayallowsuccessfulresuscitationinmanyinstances.InitialmanagementshouldincludeCPRifthevictimisnotbreathingorispulseless.Furthercoreheatlossshouldbepreventedbyremovingwetgarments,insulatingthevictim,andventilatingwithwarmhumidifiedair/oxygentohelpstabilizecoretemperature.Coretemperatureandcardiacrhythmshouldbemonitoredintheprehospitalsetting,ifpossible,andCPRshouldbecontinuedduringtransport.In-hospitalmanagementshouldconsistofrapidcorerewarmingintheseverelyhypothermicvictimwithheatedhumidifiedoxygen,centrallyadministered

warmIVfluids(43C),andperitonealdialysisuntilextra-corporealrewarmingcanbeaccomplished.Postresuscitationcomplicationsshouldbemonitored;theyincludepneumonia,pulmonaryedema,cardiacarrhythmias,myoglobinuria,disseminatedintravascularthrombosis,andseizures.Thedecisiontoterminateresuscitativeeffortsmustbeindividualizedbythephysicianincharge.

[WeinbergAD:Hypothermia.AnnEmergMedFebruary1993;22(Pt2):370-377.]

OVERVIEWOFISSUES

Severeaccidentalhypothermia(bodytemperaturebelow30C)isassocia tedwithmarkeddepressionofcerebralbloodflowandoxygenrequirement,reducedcardiacoutput,anddecreasedarterialpressure.Victimsmayappearclinicallydeadbecauseofmarkeddepressionofbrainandcardiovascularfunction:fullresuscitationwithintactneurologica lrecoveryispossib le,althoughunusual.{1}Mostclinicallysignificantepisodesofhypothermiaresultfromaninjuryinacoldenvironment,submersionincoldwater,oraprolongedexposuretolowtemperatureswithoutadequateprotectiveclothing.Thevictimsperipheralpulsesandrespiratoryeffortsmaybedifficulttodetect,butlifesavingproceduresshouldnotbewithheldbasedonclinicalpresentation.

Theveryyoungandtheveryoldaremostsusceptibletohypothermia.{1-3}Ininfants,corebodytemperaturewillcoolmorequicklythaninadults,asinfantshavealarger
http://www.hypothermia-ca.com/res-q-air.htmhttp://www.hypothermia-ca.com/res-q-air.htmhttp://www.hypothermia-ca.com/res-q-air.htmhttp://www.hypothermia.org/links.htmhttp://www.hypothermia.org/index.htmlhttp://www.hypothermia.org/inwater.htmhttp://www.hypothermia.org/animalhypo.htmhttp://www.hypothermia.org/hypothermia2.htmhttp://www.hypothermia.org/hypothermia4.htmhttp://www.hypothermia.org/hypothermia1.htmhttp://www.hypothermia.org/hayward.htmhttp://www.hypothermia.org/weinberg.htmhttp://www.hypothermia.org/fieldchart.htmhttp://www.hypothermia.org/publications.htmhttp://www.hypothermia.org/hypothermia.htmhttp://www.hypothermia.org/jama.htmhttp://www.hypothermia-ca.com/IV-warmer.htmlhttp://www.hypothermia-ca.com/res-q-air.htmhttp://www.hypothermia-ca.com/res-q-air.htmmailto:[email protected]://www.hypothermia.org/links.htmhttp://www.hypothermia.org/index.htmlhttp://www.hypothermia.org/onland.htmhttp://www.hypothermia.org/inwater.htmhttp://www.hypothermia.org/animalhypo.htmhttp://www.hypothermia.org/hypothermia2.htmhttp://www.hypothermia.org/hypothermia4.htmhttp://www.hypothermia.org/hypothermia3.htmhttp://www.hypothermia.org/hypothermia1.htmhttp://www.hypothermia.org/hayward.htmhttp://www.hypothermia.org/weinberg.htmhttp://www.hypothermia.org/hospitalchart.htmhttp://www.hypothermia.org/fieldchart.htmhttp://www.hypothermia.org/publications.htmhttp://www.hypothermia.org/hypothermia.htmhttp://www.hypothermia.org/jama.htmhttp://www.hypothermia.org/protocol.htm


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IV WARMER

TESTIMONIALS

from field

experiences

Testimonial 1Mayday

Shorelines

, . cannotproduceasmuchheatasadults.Olderindividualshavealowermetabolicratethantheyoung;thus,itismoredifficultforthemtomaintainnormalbodytemperaturewhenambienttemperaturesdropbelow18C.Agingalsoseemstobeaccompaniedbychangesintheabilitytodetecttemperaturechanges:olderpeop lemaynotseekshelterearlyenoughtoavoidbecominghypothermic.

Submersionincoldwatercancoolthecorebodytemperaturemuchmorerapidlythanexposuretocoldair,becausethermalconductivityofwateris32timesgreaterthanthatofair.{4}Hypothermiaalsocanoccurinrelativelywarmwaterconditionsifexposureis

longenoughandifcoretemperaturelossisincreasedbyconcurrentingestionofalcohol.

Alcoholingestionincreasestheriskofacquiringoraggravatinghypothermiabycausingcutaneousvasodilation(whichpreventsvasoconstriction),impairmentoftheshiveringmechanism,hypo thalamicdysfunction,andadecreaseinawarenessofenvironmentalconditions.{5-7}Othermedicalconditionsthatmaycausehypothermiaincludesepsisintheelderly(throughcentralmechanisms),hypothyroidism(throughdecreasedmetabolicrate),hypopituitarism,hypoadrenalism,headinjury(centralmechanisms),drugingestion(especiallybarbituratesorphenothiazinesthroughtheiractionsonthecentralnervoussystem),anddiabetes(especiallywhenhypoglycemiaispresent).

ClinicalFeatures

Ascorebodytemperaturedeclines,thebasalmetabolicrateandoxygenconsumptiondropgraduallybutprogressively.{3,4}Mildhypothermia(34to


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Oxygenationandacid -base balancealsocanbealteredbyhypothermia,withtheinitialmanifestationofmildhypothermia(34Corhigher)beinghyperventilation.

Ta bleKeyfindingsatdi fferentdeg reesofhypo thermia

Temperature(C)ClinicalFindings

{37}Normaloraltemperature

{36}Metabolicrateincreased

{35}Maximumshiveringseen/impairedjudgment

{33}Severecloudingofconsciousness

{32}Mostshiveringceasesandpupilsdilate

{31}Bloodpressuremaynolongerbeobtainable

{28~3O}

Severeslowingofpulse/respiration

Increasedmusclerigidity

Lossofconsciousness

Ventricularfibrillation

{27} Lossofdeeptendon.skinandcapillaryreflexes

Patientsappearclinicallydead

Completecardiacstandstill

Asdocumentedbylow-registeringthermometer.

Asthecoretemperaturedecreases,thereisrespiratorydepressionwithsubsequenthypoxemiaandhypercarbia.{3}Acombinedrespiratoryandmetabolicacidosismayoccurduetohypoventilation,carbondioxideretention,reducedhepaticmetabolismoforganicacidduetodecreasedperfusionoftheliver,andincreasedlacticacidproductionfromimpairedperfusionofskeletalmuscleandshivering.{3-8}Thereis

somecontroversyaboutwhetherarterialbloodgasesshouldbecorrectedfortemperatureinthehypothermicpatient,althoughrewarmingusuallycanbeexpectedtocorrectthemetabolicimbalanceafterthenormalcirculationisreestablished.{5-3-14}Metabolicacidosiscanbeseeninhypothermicpatientsandmaynotrespondtobicarbonatetreatment.{15}

Hypothermiaaffectsthefunctionofallorgansystems.{4}Itcancausetheinhibitionofreleaseofantidiuretichormoneanddecreaseoxidativerenaltubularactivity,causingdiuresisandvolumedepletion.{16}Thehematocritmaybeelevatedduetodehydrationandspleniccontraction,{4}andplasmaviscosityhasbeenfoundtoincreaseasthecoretemperaturefallsbelow27C{4}.Hyperglycemiaalsomaybeseeninhypothermicpatientsduetodecreasedinsulinreleaseandinhibitionof

peripheralutilizationofglucose.Thisconditionoftenwillbereversedwithrewarming,althoughtheuseofinsulinrarelymaybenecessaryinspecificcases.{17}Shivering,ifprolonged,maycausehypoglycemia,asglycogenstoresmaybecomecompletelydepleted.Hypoglycemiaalsomaybeaninitiallaboratoryfindinginpatientswhohavebeenexposedtolong-lastingphysicalenduranceandexhaustionandoftencanbe

notedinalcoholicpatients,whoalreadymayhavedepletedglycogenstores.{18}

Themammaliandivingreflexmaybeinvokedinpediatricsubmersionvictims.Facialcoolingtriggersapneaandcirculatoryshuntingtothebrainandheart,{15}whichmayproveprotective.Thisreflexalsomayoccurinadults,althoughtheclinicalsignificanceremainsunclear.{19}


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General PrinciplesofTreatment

Earlyrecognitionofhypothermiaisessentialtomaximizesurvival.Prehospitalemergencypersonnelandemergencydepartmenthealthcareprovidersmustmaintainahighindexofsuspicioninanypatientwithanalteredlevelofconsciousnesswhomayhavebeensubjectedtoevenamodestlycoolenvironment.Allemergencytreatmentfacilitiesmusthaveathermometercapableofregisteringatemperatureof30Corless.Emergencyhealthcareprovidersinareaswherecoldweatheremergenciesmaybeexpectedalsomustbeequippedwithandtrainedtouselow-registerthermometers

(tympanicorrectalprobes)andappropriaterewarmmgequipment.

MovementBecausethecoldheartisirritab leandsusceptibletoseriousarrhythmias(suchasVF),allpatientswithapulseshouldbemovedgentlyduringtransportationorduringtransferofthepatientfromastretchertoahospitalbed.Thepatientideallyshouldhavevitalsigns,coretemperature,andcardiacrhythmmonitoredcontinuouslyduringtransportation,andequipmentforresuscitation(includingadefibrillator)shouldbeimmediatelyavailable.Wheneverpossible,ahorizontalpositionshouldbemaintainedduringmovementinordertominimizeanypotentialorthostaticbloodpressuredropduetocold-inducedcardiovascularrefleximpairment.

LaboratoryTests

Whenpossible,routinelaboratoryevaluationshouldbeaccomplished,includingarterialbloodgases(ABGs),acompletebloodcount,prothrombintime,partialthromboplastintime,glucose,electrolytes,bloodureanitrogen,serumcreatinine,amylase,liverfunctiontests,ECG,chestradiography;andurinalysis.Thesetestswillallowabase linetobeestablishedandwillbemostusefulinthepostresuscitativeperiodwhencomplicationscanoccur.ThereisgeneralagreementthatABGsneednotbecorrectedduringthehypothermicphase,asrewarmingwillcorrectallhypothermic-inducedalterations.Rewarmingremainstheprimarytreatmentinseverehypothermiaforanyabnormalitiesdetected.

Interventions

Itisimportanttostressthattheseverelyhypothermicheart(


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victimsincardiacarrestorunconscioushypothermicpatientswithaslowheartrate.

Drugspertinentforresuscitationalsomaybeneededinreduceddosages,atlessfrequentintervals,orboth.Nospecificguidelinesexistonwhatreduceddoseshouldbetried,but,ingeneral,thelowestknowneffectivedosecanbetriedinitiallyifmedicationisindicated.Likewise,therearenospecificrecommendationsonchangingtheintervalofmedicationadministration,butdoublingtheusualrecommended timebetweendoseswouldbetheinitialintervalrecommended.However,medications,ingeneral,shouldbeavoidedinthehypothermicpatientincardiacarrestuntilthecoretemperatureisabove30C.Hypoglycemia,ifpresent,canbetreatedwithIVglucose.

Volumedepletionisacommonclinicalfindingintheseverelyhypothermicpatient,andIVfluidsareindicated.Theusualparametersforfluidassessmentmaybedifficulttouseinahypothermicvictim,duetolargequantitiesoffluidinthe"thirdspace"andtheclinicaldifficultyofobtainingorthostaticbloodpressuresandweight.Itshouldbeemphasizedthatperipheralaccessmaybequitelimitedduetovasoconstriction,andacentrallinemayneedtobeplaceduponarrivalintheED.IVinfusionsets,urinarycatheters,suctiontubes,andendotrachealtubesmaybecomestiffandbreakifnotpre-warmedpriortopre-hospitaluse.IVsolutionsalsoshouldbepreventedfromfreezing.butstandardformulationsofsalineanddextrosesolutionscanbeusedsafelyafterthawingifnovisibleprecipitatesarepresentandthebagsareintact.

IVfluidsshouldbewarmedtoapproximately43Cpriortoadministrationinthepre-hospitalsettingtopreventfurthercorecooling.Methodstowarmfluidsincludeusingstandardbloodwarmersadaptedforsalinebaguseorportablebattery,operatedIVlinewarmers,preheatingsalineIVbagsandstoringtheminheatedcarryingpacks,andmicrowavingliterbagsofsalinewithinsulationduringadministration.TheuseofaninsulationbarrieraroundallIVtubingandsolutionscanhelppreventheatlossfromwarmedsolutionsincoldenvironments.

Pre-hospitalManagementThedilemmaofanormothermiccardiacarrestinacoldenvironment(e.g.amiddle-agedmanwhohasanormothermiccardiacarrestwhileshovelingsnowandsubsequentlybecomeshypothermic)maypresentaconfusingclinicalpicture.Basiclifesupportandadvancedcardiaclifesupport(ACLS)shouldbe

institutedassoonasfeasible,andtheappropriatenormothermicACLSalgorithmshouldbefollowed.Rewarmingtechniquesmaybe addedtoassistintheresuscitativeeffort.TheFigurepresentsarecommendedhypothermiatreatmentalgorithm.Thisalgorithmpresentstherecommendedactionsthatprovidersshouldtake forallpossiblevictimsofhypothermia.Oncehypothermiaissuspected,everyeffortshouldbemadetopreventfurthercoretemperaturelossbyinsulationandbyremovingwetgarmentsandtocautiouslytransportthepatienttoanappropriatetreatmentfacility.

IncreasingbodytemperaturebyaggressiveexternalrewarmingtechniquesbeforeCPRisunderwaywillonlyincreasethemetabolicdemandsofthebodywithoutanyaccompanyingincreaseinblood supply,thusincreasingthechancesofinfarctionorgangrene.Wetgarmentsshouldberemovedcarefullyandreplacedwithdry(preferablywarm)garments.{4-20}Blanketsand/oraninsulatedsleepingbagmaybe

usedtoretainbodyheat,andeffortsshouldbemadetoshieldthevictimfromwindchill.Coldsleepingbagsshouldbeprewarmedwithavolunteerpriortoplacingavictiminsidetopreventcoretemperatureheatloss.Prehospitalpersonnelmaylie(strippedtotheirunderwear)alongsideaconsciousvictimunderneaththecoverstoassistinrewarming.Airwaytreatmentswithportableunitsthatcandeliverwarm,humidifiedair/oxygenheatedto42-46Ccanbeusedtodonateheatbacktothecoreandimprovethepatient'sheatbalance.{21}Exerciseisnotrecommendedasarewarmingstrategy(unlesscoretemperatureisabove35C)topreventfatalarrhythmiassecondarytoperipheralvasodilationleadingtoadeclineinbloodpressureaswellascausingcoolbloodtoreturntothecentralcirculation.{22}Afterdrop,adropincoretemperatureafterresuscitationeffortshavebegun,mayoccurthroughsignificantheatconductionfromthecoreofthebodytomoreperipherallayerswhichhave notbeenrewarmed.{23}


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ECGmonitoringshouldbeperformedintheprehospitalsettingwheneverpossibleduringresuscitationandtransport.Prehospitalpersonnelalsoshouldbeawarethatadhesivepadsformonitorleadswillnotsticktocoldskin,andconductionofelectricalsignalsacrosscoldskinmaybeimpairedinsuchsettings.Inpatientswithmoderate-to-severehypothermiainwhomsuchconductionofECGsignalsisaffected,needleelectrodesmayneedtobeinserted.Theneedlemaybeaninjectionneedlepuncturedthroughthegel-foamofaconventionaladhesivepadwhichisthen.inturn,connectedtotheECGelectrodeofthemonitor.Thismethodavoidstheneedtohavespecia lly-madeneedleelectrodesforeachmachine.Incoldenvironmentsinwhichcontinuous

monitoringisdesired,tinctureofbenzoinmaybeneededtomaintaincontactofthemonitorleads.TheQRSamplitudeshouldbemaximallyamplifiedifnocomplexesareseeninitially.

Mostelectricalmedica ldevicestobeusedintheprehospitalsetting(defibrillatorsandmonitors)haverecommendedoperatingtemperaturesabove 15.5C,andcircuitbreakersongeneratorsandpowerdistributionboardsshouldbecheckedoftentopreventfreezing.Anyrequiredmonitoringequipmentforprehospitaluseshouldbeproperlyinsulatedpriortoutilization.Batteriesareaffectedbyverylowtemperatures,whichmayaffectperformanceofequipment.

MildHypothermia(34Cto35C)

Patientswithmildhypothermia(34Corabove)generallyhaveagoodprognosisregardlessoftherewarmingmethodused.{4-8}Intheconsciouspatient,externalrewarmingisappropriate,eitherpassivelybyusingblanketsoractivelyusinghotwaterbottles,warmbaths,orchemicalheatpacksplacedunderthearmsandontheneck,chest,andgroin.These methodscanallowthepa tienttowarmatarateof0.5Cto1Cperhour.Althoughquiteeffective,warmbathshavethedisadvantageofnotallowingthecardiacrhythmtobemonitored.Roughmovementsshouldbeavoided,asdiscussedabove.Wetclothingshouldberemovedcarefully,andthepatientshouldbeinsulatedandprotectedfromwindchill.Thepatientshouldbecautionednottoexerciseasamethodofrewarmingbecauseofthepotentialforcardiovascularcollapse.Prognosisusuallyisquitegood.

ModerateHypothermia(30Cto33.9C)Pre-hospitaltreatmentofmoderatehypothermiashouldincludeallthebasicmeasureslistedaboveexceptexternalrewarming.CPRshouldbeinitiatedpromptlyifthepatientisincardiacarrest,althoughpulseandventilationsmayneedtobecheckedforlongerperiodsoftimetodetectminimalcardiopulmonaryefforts.Therecommenda tionthatpulseandventilationsbecheckedforonetotwofullminutespriortoinitiatingCPR{24-25}isprobablyexcessive.Amaximumof45secondsshouldbeadequatetimetoconfirmpulselessnessorprofoundbradycardiaforwhichCPRwouldberequired.Lossofpupilreflexes,hyporeflexia,absentbloodpressure,andlackofresponsetopainfulstimulimaynot

indicateclinicaldeathinthehypothermicpatient.Aroutinesearchforexternaltraumashouldbeaccomplishedbyprehospitalpersonnel,andtreatmentshouldbeinitiated

(e.g.,pressuredressings,etc.).Obviousphysicalevidenceofdeathwouldmitigateagainstbeginningresuscitation(e.g.,grossevisce ration,decomposition,decapitation).Stiffnessofthevictim'sbody,whichcanbecausedbyhypothermia,shouldnotbeconfusedwithclassicrigormortis.

Rewarmingisnotthemirrorimageofthecoolingprocess,especiallyforpatientswhohavedevelopedmoderate-to-severehypothermiaoveraprolongedperiodoftime.Attemptsatrewarmingsuchpatientsbyapplicationofexternalheat(suchasheatlamps,electricblankets,chemicalheatpacks,etc.)arehazardous,becausesuchinterventionswillcausesuddenperipheralvasodilationandallowcold,lacticacid-richbloodtoreturntothecoreandcauseaconvectiveafterdropincoretemperatureandpH,{21-23}increasingthelikelihoodofVE.{4}


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Minimizingconvectiveafterdropbypreventingreturnofcoo l.peripheralbloodandbydonatingheattothecoreduringinitialmanagementisakeygoa l.Thisisaccomplishedbypassiverewarmingandstabilizationmethods(coveringwithblankets,blockingexposuretowind,andremovingwetgarments).Mostafterdropsoccurduringthefirstfewminutesoftreatment,andrewarmingeffortsinthisgroupofhypothermicvictimsshouldbedirectedtothecore(warmhumidifiedoxygenorair;warmedIVfluids).

Inthehospitalsetting,patientswhoareconsciousandhaveaneffectivecirculationalsomaybetreatedwithexternalrewarmingtotruncalareasonly,butconstantmonitoringmustbemaintainedtodetectanypotentialafterdropthatcanoccur.

SevereHypothermia(


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Techniquesthatcanbeusedforrapidcorerewarmingincludetheadministrationofheated,humidifiedoxygen(42Cto46C).warmed(43C)IVfluids(normalsaline)infusedcentrallyatratesofapproximately150to200ml/hr(note:avoidoverhydration),peritonealdialysiswithwarmed(43C)potassium-freedialysateadministeredtwolitersatatime(nodwelltime),and/orextra-corporealbloodwarmingwithpartialbypass.{4-5-20-25}Acomplicationofove rvigoroushydrationispulmonaryedema,whichcanbetreatedwithstandardmedicationsafteraneffectivecirculationisrestored.Extra-corporealrewarmingshouldbeutilized,ifavailable,intheseverelyhypothermicpatient,

asthiswillallowthemostrapidandcontrolledcorerewarming.{9}TheuseofesophagealrewarmingtubeshasnotbeenreportedintheUnitedStates,althoughtheyhavebeenutilizedextensivelyinEuropeinhospitalswithoutextra-corporealrewarmingequipment.{28}Pleurallavagewithwarmsalineinstilledthroughachesttubealsohasbeenusedsuccessfully{26-29}toincreasecoretemperatureasmuchas2.5Cperhourbuthasthemajordisadvantagesofpossibleinfection,bleeding,andtherequirementforlargevolumesoffluid.Theroutineadministrationofsteroids,barbiturates,orantibioticshasnotbeendocumentedtobeofanyhelpinincreasingsurvivalordecreasingpostresuscitativedamage .{30}Additionally;theuseoflactatedRinger'ssolutionmaybedangerousduetoreducedhepaticmetabolismoflactateinthehypothermicstate.{25}

Bradycardiamaybephysiologicinseverehypothermia,andcardiacpacingisusually

notindicatedunlessbradycardiapersistsafterrewarming.Thetemperatureatwhichdefibrillationfirstshouldbeattemptedandhowoftenitshouldbetriedintheseverelyhypothermicpatienthave notbeenestablishedfirmly.Therearealsoconflictingreportsabouttheefficacyofbretyliumtosylateinthissetting,{31-32}althoughitmayprovehelpfulinVFbydecreasingthedefibrillationthreshold.

Recentlyarterialandvenouscathetershavebeenutilizedtocreateacirculatoryfistulathroughwhichtheblood isheatedbyamodifiedcommerciallyavailablecountercurrentfluidwarmer,thusachievingamoresimplifiedextracorporealrewarmingmethod.{33}Heparin-freesystemsarenowbecomingavailable{34}whichmaypreventaggravationofcoagulopathiesseeninhypothermicpatients.Radiofrequencyrewarmingisstillbeingdeve lopedasamethodofrapidcorerewarming.{35}

Continuouscoretemperatureandcardiacmonitoringshouldbeperformed,aswellasplacingaurinarycathetertomonitorurineoutput.Pulseoximetersdonotworkwellinvasoconstrictedhypothermicpatientsandwillnotaccuratelyreflectoxygenation.{5}

Postresuscitativecomplicationsmayincludepneumonia,pulmonaryedema.atrialarrhythmias,acutetubularnecrosis,acutepancreatitis,compartmentsyndromes,disseminatedintravascularcoagulation,hypophosphatemia,hemolysis,intravascularthrombosis,myoglobinuria,seizures,andtemporary,adrenalinsufficiency.{4-5-36}

Severeaccidentalhypothermiaisaseriousandpreventablehealthproblem.Cliniciansshouldlookfor''urban"hypothermiaininnercityareas,whereithasahighassociation

withpovertyanddrugandalcoholuse.{37-38}Inruralareas,over90%ofhypothermicdeathsareassociatedwithelevatedbloodalcohollevels.{39}

TerminatingResuscitativeEfforts

SomecliniciansbelievethatpatientswhoappeardeadafterprolongedexposuretocoldtemperaturesshouldnotbeconsidereddeaduntilcoretemperaturesarenearnormalandCPRstillelicitsnoresponse.Ifdrowningprecededthevictim'shypothermia,successfulresuscitationmaybeunlikely.Hypothermicvictimsshouldbetreatedaggressively,becauseevenwhenallvitalsignsareabsent,survivalwithoutneurologica limpairmentmaybepossib leincertainpatients.Althoughsomeinvestigatorshavesuggestedelevatedpotassiumasamarkerforpooroutcome,{40}


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nospec cc emca n ca o rcanpre c w comp e e accuracyw ow recover. eoldclinicalmaximthatnooneispresumeddeaduntiltheyhavebeenrewarmedtonearnormaltemperaturescannotbeappliedliterallyinallcases.Rewarmingefforts,ingeneral,probablyshouldbecontinueduntilcoretemperatureisatleast32Candmaybediscontinuedifthepatientcontinuestoshownoeffectivecardiacrhythmandremainstotallyunresponsivetoalltreatment.However,thedecisiontoterminateresuscitationmustbeindividualizedbythephysicianinchargeandshouldbebasedontheuniquecircumstancesofeachincident.

Successfultreatmentofhypothermiarequiresoptimaltrainingofemergencypersonnel

andappropriateACLSresuscitationmethodsateachinstitution.Becauseseverehypothermiaisfrequentlyprecededbyotherdisorders(e.g.,drugoverdose,alcoholuse,trauma,etc.),theclinicianmustseekandtreattheseunderlyingconditionswhilesimultaneouslytreatingthehypothermia.

COMMENTARY

Theintroductionofanewalgorithmforthetrea tmentofhypothermiawillfacilitatetheteachingofbasicassessmentandrewarmingtechniquestoallhealthcareproviders.Forhypothermicvictimsintheprehospitalsetting,theuseofCPR,removingwetclothingandshelteringfromwindchill,andstabilizationwithwarmedair/oxygenandIVfluidsconstitutetheinitialtreatmentmodalities.In-hospitalrewarmingandmanagementcanrequireintubation,centrallineplacement,warmedperitonealdialysatelavage,andextracorporealtreatment.Closepostresuscitativemanagementwillrequireclosein-hospitalobservationforavarietyofpotentialpulmonary,hematologic.andrenalcomplications.

RESEARCHINITIATIVES

AdditionalresearchontheuseofbretyliumandotherantiarrhythmicmedicationsinhypothermicVFclearlyisindicated,aswellasresearchondosingandintervalreductionsrequiredwhenadministeringmedicationsinhypothermicvictims.EvaluationoftheidealtemperaturetofirstattemptdefibrillationinpatientswithhypothermicVFalso

needstobeconducted.Furtherresearchonmicrowaverewarmingofhypothermicpatientsandotherprehosp italrewarmingtechniquesneedsexpansion.


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Hypothermiatreatmentalgorithm-fullsize(1038x1706)

(a)Mayrequireneedleelectrodesthroughtheshin.

(b)Manyexpertsthinkthisshouldbedoneonlyin-hospital.(c)Methodsincludeelectricorcharcoalwarmingdevices,hotwaterbottles,heatingpads,radiantheatsources,andwarmingbeds.(d)EsophagealrewarmingtubesarewidelyusedinEurope.

Abbreviations:

VF=ventricularfibrillationVT=ventriculartachycardiaJ=joulesKCL=potassiumchloride

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Theauthorgreatlyacknowledgestheadvice andcontributionofDrsRogerDWhite,Richard0Cummins,SveinHapnes,MadsGilbert,KristianLexow.andJamesLPaturas,EMT-P,inthedevelopmentofthismaterial.


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