Resuscitation 81 (2010) 645652

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Resuscitation

journa l homepage: www.e lsev ier .com/ locate / resusc i ta t ion

Review

Prognostic factors in avalanche resuscitation:A syste

Jeff Boyda Department ob Internationalc EURAC Institud Innsbruck Me

a r t i c l

Article history:Received 30 NReceived in reAccepted 18 January 2010

Keywords:AvalancheSnowAsphyxiaHypothermiaAirwayTemperaturePotassiumResuscitationRescue

cardiac arrest.Methods: Time of burial, airway patency, core temperature and serum potassium level were analyzedas PICO (Patient/population, Intervention, Comparator, Outcome) questions within the 2010 Consensuson Science process of the International Liaison Committee on Resuscitation. The electronic databases of

Contents

1. Backg2. Metho

2.1.2.2.2.3.

3. Result3.1.3.2.3.3.

4. Discu4.1.

A Spanish Correspon

E-mail adda Our interp

on January 5th

0300-9572/$ doi:10.1016/j.Medline via PubMed, EMBASE via OVID and the Cochrane Database of Systematic Reviewswere searchedusing combinations of the search terms avalanche, air pocket, hypothermia and serumpotassium.Results: Of 1910 publications that were identied 30 were found relevant. The predictive value for sur-vival of a short time of burial or a patent airway after 35min of burial is supported by 10 retrospectivecasecontrol studies, 4 case series and 2 experimental studies, while no studies are neutral or opposed.A core temperature of less than 32 C with a patent airway is supported by 2 retrospective casecontrolstudies and 3 case series, while 10 studies are neutral. Serum potassium level is supported by 6 retro-spective casecontrol studies and 3 case reports, while 3 retrospective casecontrol studies and 1 animalmodel are neutral.Conclusion: After 35min of burial, or where the core temperature is less than 32 C, a patent airwayis associated with survival to hospital discharge. A serum potassium of less than 7mmol/L may be avaluable indicator for survivalwhenother indicatorsareunclear. Thesendings shouldmodify thecurrentavalanche resuscitation scheme.

2010 Elsevier Ireland Ltd. All rights reserved.

round . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 646ds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 646Prognostic factors as PICO questions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 646Search strategy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 646Evidence appraisal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 646s . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 646Time of burial and airway patency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 648Core temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 648Serum potassium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 649

ssion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 650Interpretation of evidencea and recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 650

translated version of the abstract of this article appears as Appendix in the nal online version at doi:10.1016/j.resuscitation.2010.01.037.ding author at: Department of Emergency Medicine, Mineral Springs Hospital, Banff, AB, Canada. Tel.: +1 403 762 4974; fax: +1 403 762 4193.ress: jbavresus@telus.net (J. Boyd).retation of the evidence incorporates the ndings of the Consensus on Science developed by the Advanced Life Support Task Force during a web conference, 2009.

see front matter 2010 Elsevier Ireland Ltd. All rights reserved.resuscitation.2010.01.037matic review

a,b,, Hermann Bruggerc,d, Michael Shustera

f Emergency Medicine, Mineral Springs Hospital, Banff, AB, CanadaFederation of Mountain Guides, Banff, Alberta, Canadate of Mountain Emergency Medicine, Bozen/Bolzano, Italydical University, Innsbruck, Austria

e i n f o

ovember 2009vised form 12 January 2010

a b s t r a c t

Objective: Avalanche resuscitationwill save lives if focussed on victims that have the potential to survive.The purpose of this systematic review was to examine 4 critical prognostic factors for burial victims in

646 J. Boyd et al. / Resuscitation 81 (2010) 645652

4.1.1. Time of burial and airway patency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6504.1.2. Core temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6504.1.3. Serum potassium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651

4.2. The ICAR MedCom avalanche resuscitation algorithm. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6514.3. Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4.4. Future research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

5. Authors conclusions and recommendations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Disclaimer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Conict of interest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Source of support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Refer . . . . . .

1. Backgro

Avalanchtwenties.1,2

also a commMortalit

depends onare often unining potengrossly inscase inwhicyoung buriaafter 150mwithout necitation ofoutcomes.7

As the menvironmentool is critic

These fanational Coan avalanchon a narratthe mountaburied victiof burial, aserum potareported toresuscitatioThe aim ofliterature ifactors in timproveme

2. Method

Time ofpotassium wOutcome (Pevidence evon Resuscitwere subjecand draft Cowere review

b A patent aor other meanmouth and notherefore the ncan easily befactor throughmore reliably

ogno

Forimeict sForurieirwaict sFor aorepatC), pForf serotas

arch

eleche se(air pAND

avalaings wawordnallistsed.

articlsnow

eview

iden

airwed batenrums.ences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

und

es kill healthy people, most commonly in theirAsphyxia causes most deaths35 although trauma ison cause of death.2

y is 70% when there is complete burial and rescueorganized teams.6 Victims who are in cardiac arrestder- or over-resuscitated. The authors of a study exam-tial prognostic factors observed that resuscitation wasufcient for some victims.7 Another report describes ah standardBasic Life Support (BLS)waswithheld fromal victim during transport, yet cardiopulmonary bypassin of cardiac arrest resulted in discharge from hospitalurological impairment.8 Conversely, exhaustive resus-victims of prolonged asphyxia leads to generally poor,911

edian number of victims per incident is four12 and thet is resource-poor,11 an evidence-based managemental for on-scene triage.ctors prompted the Medical Commission of the Inter-mmission for Alpine Rescue (ICARMedCom) to develope resuscitation algorithm (Fig. 1), which they basedive review of 49 publications and consensus amongin rescue physicians.13 The algorithm is designed forms and incorporates 4 critical prognostic factorstimeir pocket with patent airway, core temperature andssium level. Application of this algorithm has beenprompt appropriate resuscitation8 and to prevent futilen efforts in victims with no likelihood of recovery.14,15

our study is to perform a systematic review of then order to examine the scientic basis of prognostiche avalanche resuscitation algorithm and to identifynts.

s

burial, airway patency,b core temperature and serumere examined as Population Intervention Comparator

ICO) questions within the 2010 Consensus on Sciencealuationprocess of the International LiaisonCommitteeation (ILCOR).16 Search strategy and evidence appraisalted to critical evaluationby the ILCOR reviewingexpert,

2.1. Pr

2.1.1. td

2.1.2. bad

2.1.3. ca(

2.1.4. op

2.2. Se

Thewith tAND (sium))with ({IncludReviewor KeyAdditioerenceperform

Alltion topeer-r

2.3. Ev

Asextendway pand sestreamnsensus on Science and Treatment Recommendationsed by the Advanced Life Support (ALS) Task Force.

irway is dened as an airway not obstructed by avalanche debriss. The air pocket has been dened as any space surrounding these, no matter how small, with a patent airway.11 A patent airway isecessary component of the denition of the air pocket. Air spacesoverlooked.11 Patent airway is therefore used as the prognosticout this review in place of air pocket because patent airway isidentied by a rescuer.

Eligibleof evidenceby ILCOR.16

neutral or o

3. Results

Our sealistings anded 149 ar. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 651

stic factors as PICO questions

avalanche victims in cardiac arrest (P), does a shorterof burial (I), compared to longer time of burial (C), pre-urvival to hospital discharge (O)?avalanche victims in cardiac arrest who have beend longer than 35min (P), does the presence of a patenty (I), compared to absence of a patent airway (C), pre-urvival to hospital discharge (O)?valanche victims in cardiac arrestwho are foundwith atemperature of less than 32 C (P), does the presence ofent airway (I), compared to absence of a patent airwayredict survival to hospital discharge (O)?avalanche victims in cardiac arrest (P), do lower levelsum potassium (I), compared to higher levels of serumsium (C), predict survival to hospital discharge (O)?

strategy

tronic database of Medline was searched via PubMedarch terms (avalanche [All Fields]), (((hypothermia))ocket))) and (((Hypothermia[Mesh])) AND ((potas-survival) and the database of EMBASE via OVID

nche {Including Related Terms}) and (hypothermiaRelated Terms}). The Cochrane Database of Systematics searched with the terms (avalanche in Title, Abstracts) and (hypothermia in Title, Abstract or Keywords).hand searching of review articles, reference texts, ref-and conference proceedings for relevant studies was

es describing studies on the 4 prognostic factors in rela-avalanches and hypothermia that were published in

ed journalswere considered eligible for further review.

ce appraisal

ay patency does not become signicant until afterurial the prognostic factors of time of burial and air-cy were reviewed in combination. Core temperaturepotassium were reviewed separately giving 3 reviewstudies were reviewed in detail and classied by level(LOE) (Table 1) and methodological quality as dened

,17 The evidence was further categorized as supportive,pposed to the relevant question(s).

rch identied 1910 articles. After excluding duplicatestudies not dealing with snow avalanches, we identi-

ticles that appeared pertinent and we subjected these

J. Boyd et al. / Resuscitation 81 (2010) 645652 647

Fig. 1. Avalanche resuscitation algorithm.13 Pre-hospital management of persons buried in an avalanche. *In all cases: core temperature +ECGmonitoring, gentle extrication,oxygen, airwaywarming, insulation, hot packs on trunk; 0.9% NaCl and/or 5% glucose only if an intravenous line can be establishedwithin a fewminutes; trauma treatment ifindicated. **Transport to the nearest hospital for serum potassiummeasurement if hospitalisation in a specialist unit with cardiopulmonary bypass facilities is not logisticallypossible. If K+ exceeds 12mmol/L, stop resuscitation and pronounce death by asphyxiation; if K+ is lower than, or equals, 12mmol/L, continue cardiopulmonary resuscitationand transport the patient as soon as possible to a specialist hospital for extracorporeal rewarming. ACLSadvanced cardiac life support, CPRcardiopulmonary resuscitation.Staging of hypothermia according to Swiss Society of MountainMedicine guidelines. Source: Reprinted from Resuscitation, 2001;51:715, Brugger H, Durrer B, Adler-KastnerL, Falk M, Tschirky F. Field management of avalanche victims, with permission from Elsevier.

648 J. Boyd et al. / Resuscitation 81 (2010) 645652

Table 1ILCORa levels of evidence for prognostic studies16,17.

LOE P1 Inception (prospective) cohort studies (or meta-analyses of inception cohort studies), or validation studies of a clinicaldecision rule (CDR)

LOE P2 lled ting a

LOE P3LOE P4LOE P5 n (e.g.

aInternational

Table 2Summary of le ial and

Level of evid

Quality of stuGood

Fair

a Outcome m hospb No studiesc Overlappin

to abstractleaving 30 a

3.1. Time o

Ten LOEseries and tvolunteersburial andpredict surv

Four of tvictims burairway.8,25,2

In four stburial, therand the vicvival with astudies.

In a retronon-linearrelationshipof survivalmeted to 30that asphyxhypothesizewith continvivor groupof the survhypothermairway.

A prospbreathing fstate of hyptests, at a lethat prolonof an air po

re te

o LOEseri

coret airMulermad CPingstuded 1Follow-up of untreated control groups in randomized controderivation studies of a CDR, or validation studies of a CDR usRetrospective cohort studiesCase seriesStudies not directly related to the specic patient/populatiomechanical models)

Liaison Committee on Resuscitation.

vels of evidence, quality of studies and outcome measuresa supporting time of bur

ence LOE P1 LOE P2 LOE P3

dyBrugger and Falk18 BCc

Brugger et al.13 BCc

Burtscher21 BCBuser22 et al. BCc

Falk et al.23 BCc

Hohlrieder et al.12 BELocher et al.9,24 ACMair et al.7 ADc

Grosse et al.25 BCDStalsberg et al.27 BCD

easures: A= return of spontaneous circulation; B= survival of event; C = survival towere neutral or opposed to time of burial and airway patency predicting survival.g patients.

review. We then discarded 119 articles as not relevant,rticles for full review.

f burial and airway patency

P3 retrospective casecontrol studies, four LOE P4 casewo LOE P5 studies of simulated air pockets in humanare supportive of the hypotheses that a shorter time ofthe presence of a patent airway after 35min of burialival, while no studies are neutral or opposed (Table 2).hese studies described survival to hospital discharge in

3.2. Co

TwP4 casewith aa paten

Thehypothwho hrewarm

In adescribied for longer than 60min when found with a patent7,28

udies that examined thepattern of survival over timeofe was no survivor when burial was longer than 35mintim had an obstructed airway (Table 3). Nor was sur-n obstructed airway described in any of the remaining

spective observational study, Falk et al.23 established arelationship between time of burial and survival. The, labelled the survival curve, demonstrated a rateover 90% in the rst 15min of burial but that plum-% over the next 20min (Fig. 2). The authors concludedia is the cause of this steep decline. They went on tothat survival beyond 35min would be possible onlyued breathing via a patent airway. This small sur-would then remain alive through a plateau phase

ival curve but would eventually succumb to lethalia after approximately 90min of burial, despite a patent

ective randomized crossover study found that, whenrom a simulated air pocket, subjects achieved a steadyoxia for at least 20min in 11 of 28 (39%) uninterruptedvel adequate to support life.20 The authors concludedged survival after snowburial is possible in the presencecket of even small dimensions.

were rewarin patientsburial victimery. The autdeep hypotvictims.

In a stuwere in camum coolinbetween th0.755.8) C

In a case3m depthneously brefor a coolinarrest whication. The aserum potathe patienting incompspontaneouof hypothereal circulamembranestudies (Tabrials (or meta-analyses of follow-up studies), orsplit-sample

different patient/population, animal and

airway patency predicting survivalb.

LOE P4 LOE P5

Kornberger and Mair19 BC Brugger et al.20 E

Oberhammer et al.8 CD Grissom et al.26 ERadwin and Grissom28 BCDSumann15 E

ital discharge; D= intact neurological survival; E =other end point.

mperature

P3 retrospective casecontrol studies and three LOEes support the hypothesis that victims in cardiac arresttemperature of less than 32 Cmay survive if they haveway. Ten studies are neutral (Table 4).ticentre Hypothermia Survey29 examined 401 cases ofia from various causes and found that 15 of 41 (37%)R survived while 5 of 16 (31%) who had extracorporealsurvived.y of 234 severely hypothermic victims Walpoth et al.30

5 survivors out of 36 (42%) cardiac arrest victims who

med with cardiopulmonary bypass. Core temperatureswith cardiac arrest were all below 28 C. One avalanchewith the core temperatureof 19.6 Cmadea full recov-

hors ascribed good outcomes to the protective effect ofhermia, good rescue organization and young healthy

dy of 32 hypothermic avalanche victims, 19 of whomrdiac arrest, Locher and Walpoth24 found the maxi-g rate under the snow was 8 C/h. Subsequent coolinge accident site and the hospital averaged 3 (range/h.report8 of a hypothermic avalanche victim buried at

for 100min, the victim was unconscious but sponta-athing on extrication. His core temperature was 22 Cg rate of 9 C/h. The victim then experienced cardiach was untreated during pre-hospital helicopter evacu-ttending physician at the receiving hospital found thessium to be 4.3mmol/L, initiated CPR and re-directedto a trauma centre for cardiopulmonary bypass, result-lete recoverydespite150minof cardiacarrest. Returnofs circulation (ROSC) and survival to hospital dischargermic avalanche victims rewarmed with extracorpo-tion, either cardiopulmonary bypass or extracorporealoxygenation (ECMO), has been described in 6 otherle 5).

J. Boyd et al. / Resuscitation 81 (2010) 645652 649

Table 3Studies of survival patterns compared to time of burial and airway patency.

Series Total number Survivors n (%) Pattern survival curvea Time of 30% survival (min) Survival after 35min with obstructed airway

Brugger and Falk18,b 332 150 (45) Yes 40 NoBuser et al.22,c 332 150 (45) Yes 40 NoFalk et al.23,b 442 181 (43) Yes 35 NoBrugger et al.13,b 638 334 (48) Yes 40 No

a Demonstrated a similar non-linear survival curve pattern to the key study of Falk et al.23 with a steep drop in survival to a plateau at 30% survival.b Incremental overlapping populations.c Same population as above but analyzed independently by different investigators.

Table 4Summary of levels of evidence, quality of studies and outcomemeasuresa that are supportive or neutral to the hypothesis that victims in cardiac arrestwith a core temperatureof less than 32 C may survive if they have a patent airway.

Level of evidence LOE P1 LOE P2 LOE P3 LOE P4 LOE P5

Studies supportive of prognostic factorGood Danzl et al.29 ABC Walpoth et al.30 CDb

Locher and Walpoth24 ACb

Fair Althaus et al.31 CDOberhammer et al.8 CD

Studies neutrGood Grissom et al.32 E

Fair Kornberger and Mair19 BC Grissom et al.34 E

a Outcome m hospital discharge; D= intact neurological survival; E =other end point.b Overlappinc Overlappin

3.3. Serum

Six LOEcase reportpredict survLOE P3 retmal modelstudy of 32found the s(range 3.12.018)mmasphyxia asnon-survivo

A retrospprognosticdiac arrest wof the 22 vic

Table 5Hypothermic alation rewarm

Series

Althaus et alLocher and WMair et al.7

OberhammeRuttman et aSchaller et aWalpoth et a

Total

a Core tempb Includes v

ad athose3.4-ot ROal to prognostic factorBrugger et al.13 BCc

Brugger and Falk18 BCc

Locher et al.9 ACb

Mair et al.7 AD

Farstad et al.33 CDRuttman et al.14 ACDStalsberg et al.27 BCD

easures: A= return of spontaneous circulation; B= survival of event; C = survival tog patients.g patients.

potassium

P3 retrospective casecontrol studies and three LOE P4s support the hypothesis that serum potassium levels

ROSC hwhile(rangewithouival in avalanche victims in cardiac arrest, and threerospective casecontrol studies and one LOE P5 ani-are neutral (Table 6). In a retrospective casecontrolhypothermic avalanche victims Locher and Walpoth24

erum potassium at hospital admission to be 4.250.96.4)mmol/L in survivors compared to 9.954.9 (rangeol/L in non-survivors (P=0.003). The authors identiedthe cause of hyperkalaemia and cardiac arrest in thers.ective casecontrol study by Mair et al.7 examined for

markers in patients with severe hypothermia and car-ho were rewarmed with cardiopulmonary bypass (12

timswere from avalanche accidents). Patientswho had

valanche victims in cardiac arrest treated with extracorporeal circu-inga.

Return of spontaneouscirculationb

Survival to hospitaldischarge

.31 1 1alpoth24 5 2

4 1r et al.8 1 1l.14 10 1l.10 1 1l.30 1 1

23 8

eratures were all lower than 32 C.ictims that survived to discharge.

Fig. 2. Survivprobability fo(n=735) in relin open areas(grey curve, n(buildings, roasurvivors arein buildings anfor the cut-off(P=0.001; Peafor completelydata for 1981tion, 2001;51:managementmedian serum potassium of 5 (range 3.48)mmol/Lwithout ROSC had a median serum potassium of 8.7ver 20)mmol/L. Autopsy in 8 of the avalanche victimsSC, who had admission serum potassium levels rang-al probability for completely-buried avalanche victims.13 Survivalr completely-buried avalanche victims in Switzerland 19811998ation to time (min) buried under the snow, contrasting victims buried(black curve, n=638) with those buried in buildings or on roads

=97). Median extrication times were 37min (open areas) and 56minds) (P=0.17, MannWhitney U-test). In open areas only 16.6% of allextricated after the cut-off point of 35min, as compared with 32.7%d on roads (P=0.008; Pearsons chi-square). The respective ndingspoint of 130min are 1.7% (open areas) and 16.3% (buildings, roads)rsons chi-square). The dotted curve represents the survival function-buried avalanche victims in open areas (n=422) based on the Swiss1991, calculated by Falk et al.23 Source: Reprinted from Resuscita-715, Brugger H, Durrer B, Adler-Kastner L, Falk M, Tschirky F. Fieldof avalanche victims, with permission from Elsevier.

650 J. Boyd et al. / Resuscitation 81 (2010) 645652

Table 6Summary of levels of evidence, quality of studies and outcomemeasuresa that are supportive or neutral to the hypothesis that for victims in cardiac arrest the serumpotassiumpredicts survival to discharge.

Level of evidence LOE P1 LOE P2 LOE P3 LOE P4 LOE P5

Studies supportive of prognostic factorGood Danzl et al.29 ABC

Hauty et al.35 CLocher et al.9 ACb

Locher and Walpoth24 ACb

Fair

Studies neutrGood

a Outcome m to hosItalics = anima

b Overlappin

ing from 5was asphyxvivor within cardiac aauthors connate resuscbased on laquestion thjudgment.

A retrosby Schaller2.75.3)mm14.5 (6.82They then205min aftpotassium wafter rewarcluded thatthose patie

The hightim in card6.4mmol/Lin a child ex

4. Discussi

It is critiidentify avathat we mands evidenture and seto determinadvanced re

4.1. Interpr

4.1.1. TimeCardiac

due to asphtrauma2 or

c Our interpScience develoon January 5th

resurwayoxiache doximas deche vbe atheycernr 35andesenestr

beyoing permore,or uitatiore thtruct

Coreen tirvecools thaMair et al.7 ADSchaller et al.10 AC

al to prognostic factorFarstad et al.33 CDRuttman et al.14 ACDSilvfast and Pettila39 AC

easures: A= return of spontaneous circulation; B= survival of event; C = survivall study.g patients.

.9 to over 20mmol/L, established the cause of deathia in 6 and trauma in 2. One long-term avalanche sur-the serum potassium on admission of 3.8mmol/L wasrrest for 210min with a core temperature of 24 C. Thecluded that, although a decision to continue or termi-itation in a hypothermic arrest victim cannot be madeboratory parameters, they can be used to conrm ore decision to terminate resuscitation based on clinical

pective casecontrol study of 24 hypothermic victimset al.10 found a median serum potassium of 3.5 (rangeol/L in survivors (not avalanche victims) compared to4.5)mmol/L in non-survivors (all avalanche victims).described an avalanche victim in cardiac arrest forer burial for 60min at a depth of 2m. The victims serumas 4.5mmol/L and they survived to hospital discharge

ming with cardiopulmonary bypass. The authors con-the normal serum potassium might be used to selectnts in whom heroic resuscitation efforts can be useful.est admission serum potassium in an avalanche vic-iac arrest who survived to hospital discharge was

24 while in all-cause hypothermia it was 11.8mmol/L,posed to freezing weather.36

on

cal that we nd prognostic indicators that will reliablylanche victims who have the potential to survive, so

victimitus, aior hypavalanis apprburialavalanshouldunlessas con

AfteairwayThe proften dvivedbecomhypothTherefpatentresuscfor moan obs

4.1.2.Wh

may serate offollowy effectively focus resuscitation resources. This reviewce that time of burial, airway patency, body tempera-rum potassium can provide valuable prognostic inpute who may benet from aggressive resuscitation andwarming.

etation of evidencec and recommendations

of burial and airway patencyarrest from avalanche involvement is more commonlyyxia than hypothermia11 but may also occur due toas a combination of these 3 factors. Asphyxia in a buried

retation of the evidence incorporates the ndings of the Consensus onpedby theAdvanced Life Support Task Force during aweb conference, 2009.

would havecore tempesurvival, thcore tempemore or lessof burial thshould be a

Avalancature of lto hospitacardiopulmpredominawith a counknown afor extracobe termina32 C is founDobson et al.36 CDOberhammer et al.8 CDvon Segesser et al.37 CD

Bender et al.38 E

pital discharge; D= intact neurological survival; E =other end point;

lts fromairway obstruction by avalanche debris or vom-malalignment, mechanical compression of the chest27

with hypercapnia due to poor gas diffusion throughebris.20,26,32,34 Mortality after the rst 15min of burialately 10%, then increases until it is 70% at 35min ofmonstrated by the survival curve (Fig. 2) (Table 3). Allictims found in cardiac arrest within this rst 35minctively resuscitated following BLS and ALS guidelineshave suffered lethal trauma or when other factors suchfor rescuer safety prevail.min of burial the only survivors are those with a patentthe ability to continue breathing.7,8,13,18,19,22,23,25,27,28

ce of an air pocket may be difcult to conrm as it isoyed during rescue. The 30% of victims that have sur-nd the rst 35min of burial often remain alive whilerogressivelymore hypothermic until the onset of lethalia after approximately 90min of burial (Fig. 2) (Table 3).all victims buried longer than 35min that exhibit anknown airway should be actively resuscitated whilen may be terminated in victims who have been buriedan 35min and are found in asystolic cardiac arrest withed airway.

temperatureme of burial is not known precisely, core temperatureas a reasonable proxy. Considering that the maximuming while buried has been observed to be 9 C/h,8,24 itt a victim with a core temperature of less than 32 C

been buried longer than 35min. If this victim with arature of less than 32 C is to have any possibility ofe victim must exhibit a patent airway. However, if therature is above32 C, thedurationofburialmaybeeitherthan35min. Therefore, a victimwith anunknown timeat is found with a core temperature greater than 32 Cctively resuscitated regardless of airway patency.he victims in cardiac arrest with a core temper-ess than 32 C, have achieved ROSC and survivall discharge with extracorporeal rewarming usingonary bypass or ECMO where asphyxia has notted.7,8,10,14,19,24,30,31 Therefore, victims in cardiac arrestre temperature less than 32 C with a patent orirway should be actively resuscitated and transportedrporeal rewarming when practical. Resuscitation mayted when a victim with a core temperature of less thand in asystolic cardiac arrest with an obstructed airway.

J. Boyd et al. / Resuscitation 81 (2010) 645652 651

4.1.3. Serum potassiumIn some hypothermic avalanche victims the serum potassium

may assist when details of other prognostic factors are unknownor a decision needs to bemade for prolonged resuscitation or evac-uation to amadmission swho survivhowever, a san initial pdiac arrest wor unknownshould be arewarming.avalanche vwith other fResuscitatiois greater th

4.2. The ICA

Our anaof the ICARbecause anbecause a pwe recommalgorithm.lization shodebrillatioto comply w

4.3. Limitat

All the stional in nadatabases thave consisor patent aresuscitatiobiased. Howsystematicof the algoris connedally indexehave misseever, the aloccasions incomment.8,

4.4. Future

Databasprognosticserum potaextricationavalanche brological fuavalanche bProspectiveoutcomesbnot.

5. Authors

Our revithe patency

temperature of less than 32 C contributes dependable prognos-tic input to an avalanche resuscitation scheme. A serum potassiumless than 7mmol/L is associatedwith survival to hospital dischargeand may be a valuable tool when other indicators are unclear or

tionrewampeent w

imer

s redevereatmtionanheorceach qd street.sus and Ted iclusinpuencelity i

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e oft.has pf burignos

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ey S,of theongerof intttp://wSurviJ, Ha

ancheger Hron Mlriederity otosh

ancheey S,zerlankshopssed 2llstatiP, Koatientscitatajor centre for extracorporeal rewarming. The highesterumpotassium in an avalanche victim in cardiac arrested to hospital discharge was 6.4mmol/L.24 There is,ingle case report of survival in ahypothermic childwithotassium of 11.8mmol/L.36 Therefore, a victim in car-ith a core temperature of less than 32 C with a patentairway and a serum potassium of less than 7mmol/L

ctively resuscitated and transported for extracorporealA serumpotassiumof greater than7mmol/L in an adultictim in asystolic cardiac arrest may, in combinationactors, assist in the decision to terminate resuscitation.n should be terminated when initial serum potassiuman 12mmol/L.

R MedCom avalanche resuscitation algorithm

lysis of prognostic elements conrms the soundnessMedCom avalanche resuscitation algorithm. However,air pocket may be so small as to be overlooked, andatent airway is the necessary condition for an air pocket,end substituting patent airway for air pocket in theStandard trauma precautions such as spinal immobi-uld be emphasized. Treatment interventions such asn and hypothermia management need to be modiedith the 2010 BLS and ALS guidelines.

ions

tudies on avalanche victims are retrospective observa-ture. Many have extracted information from avalanchehat are subject to reporting deciencies and may nottently identied prognostic factors such as an air pocketirway. Some studies may have followed the avalanchen algorithm after its publication and therefore beenever, 13 of the avalanche studies considered in this

review contained data collected prior to the publicationithm.7,9,10,13,18,19,2124,27,30,31,37 This systematic reviewto full text peer-reviewed publications in internation-d journals, consistent with ILCOR standards, and mayd pertinent publications in the other literature. How-gorithm has been published in its current form on 5peer-reviewed journals with no subsequent negative

13,4042

research

es should be prospectively designed to obtain data onfactors such as airway patency, core temperature andssium. Core temperatures should be documented uponto allow the calculation of accurate cooling rates forurial. Outcome data should include measures of neu-nction. Further research on the pathophysiology ofurial, including air pocket physiology, should be done.validation studies on the algorithm should compare

etween resuscitation complyingwith the algorithmand

conclusions and recommendations

ewhas found evidence that, for victims in cardiac arrest,of the airway after 35min of burial or with a core

evacuaporealcore teconsist

Discla

Thitionsand TInternaamericTask Feral, edetaileworkshconsenence apublishthe conreectconferfeasibi

Conic

Noninteres

HBtime oon pro

Source

HerInstitu

Nei

Ackno

We

Refere

1. HarvrainC, Cingsat hand

2. Boydaval

3. BrugEnvi

4. Hohseve

5. McInaval

6. HarvSwitWorAcceunfa

7. Mairin pResutoextracorporeal rewarming is contemplated. Extracor-rming techniques are recommended for victims with arature of less than 32 C when prognostic indicators areith survival and where these modalities are available.

view includes information on resuscitation ques-loped through the C2010 Consensus on Scienceent Recommendations process, managed by the

al Liaison Committee on Resuscitation (http://www.art.org/ILCOR). The questionswere developed by ILCORs, using strict conict of interest guidelines. In gen-uestion was assigned to two experts to complete a

uctured reviewof the literature, andcomplete adetailedWorksheets are discussed at ILCOR meetings to reachnd will be published in 2010 as the Consensus on Sci-reatment Recommendations (CoSTR). The conclusionsn the nal CoSTR consensus document may differ fromions of in this review because the CoSTR consensus willt from other worksheet authors and discussants at the, and will take into consideration implementation andssues as well as new relevant research.

interest

the authors has a commercial or industrial conict of

ublished studies on avalanche resuscitation examiningal and airway patency. Neither JB orMS have publishedtic factors.

upport

n Brugger receives support as the head of the EURACMountain Emergency Medicine.JB or MS receive funding for avalanche research.

gement

k Shelley Mardiros for manuscript review.

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Prognostic factors in avalanche resuscitation: A systematic reviewBackgroundMethodsPrognostic factors as PICO questionsSearch strategyEvidence appraisal

ResultsTime of burial and airway patencyCore temperatureSerum potassium

DiscussionInterpretation of evidenceb and recommendationsTime of burial and airway patencyCore temperatureSerum potassium

The ICAR MedCom avalanche resuscitation algorithmLimitationsFuture research

Authors conclusions and recommendationsDisclaimerConflict of interestSource of supportAcknowledgementReferences