This study compared the efficacy of three post-exercise cooling techniques for reducing core body temperature in hyperthermic individuals: intravenous saline infusion (IV), ice packs (ICE), or water spray and fan cooling (FAN). Eleven healthy male volunteers exercised in heat until their core temperature reached 40°C, then underwent one of the three 40-minute cooling treatments. The IV and FAN techniques reduced core temperature faster than ICE in the first 20 minutes. Three participants reported numbness from the chilled saline but symptoms resolved within 5 minutes of stopping the infusion. All three techniques were effective at reducing core temperature and suitable for emergency field use during transport to medical care.

1. Efficacyof FieldTreatmentsto ReduceBody
CoreTemperaturein HyperthermicSubiects
wADE H. sTNCLAIR',stppu,qN J. RUDZKI.,RNtttoNy s. LEICHT',ALtsoN L. r'ocRRtv3,
SUSAN K. WINTER*. andMARK J. PATTERSON'
tlttstitute
o/'Sport and Exerr:iseSc:ience,Jane.sCook Llniversih,,Towrtsville,Queenslancl,ALlSTRALIA;2Direc'torate
of
Oc:c'upationall"lealthand Sa.fetv,AustralianArmt', Canberra,Austra.lianCapitol Ten'ibn,, AUSTRALIA:'DelbnceScient'e&
TechnologvOrganisation,Melbowne, L/it:toria,ALISTRALIA;and'Att.strulianArmy, Tow'nsville,Queen,slatd,AUSTRALIA
ABSTRACT
SINCILAIR,W. H.. S. .l RUDZKI. A. S. LEICIIT. A. L. FOC;ARTY.S. K. WINTER. and M. .1.PATTERSON.Ellicacyof Field
Treahnentsto ReduceBody Corc Tempcrarturcin HypcrthennicSub.jccts.trlcd. Sti. Sltrtrt.sErt'n.. Vol. .11.No. ll. pp. l9E4 1990.
2009. Purposc: To curtrastthc cffcctsofthree postcoolingtechniquesin reclucingbody core telnperature1l) in crcrcrsc-induccd
hypertherrnicparlicipantson the cessationof exercise.Methods: Elevenliealthyactir,emale volunteersu'erc cooledduring a ,{0-min
periodusingthreedifferentmcthocls:icc packsto thc ncck.axillac.andgroin(lCE); 'atcrsprayandfan (FAN): andI L ofchillcd (10'C')
intravenoussalineatlministcrcdduring a 20-min pcriod (lV). Rateofdecrcasc in d, cardiovascularresponscs.and any incitlcnccof
reportedadvcrsccf-flcctswcrc invcstigatcd.Trialswerc presentedin a counterbalancedorderrvith the voluntcen'body corc tcrnpcraturc
beingclcvatctlto40.0"Conthrccoceasionsriaarrintcnnitlcnlu'alkmn(2rninat6krnh
land4minatl0knr'h 1)plotocol
conductccl
rvithina climatc-controlledchamber(3:1.2t 0.5"Cand62.31 3.l% relatirehunridity).Results:Rateof l, recluctiondurirrgtlreflrst20 rnin
o1'oolingwas greaterfor FAN cor.r.rparetlrvith IC'E(0.091 0.02"Cnrin
I
vs 0.07t 0.02"Crnin
r.
P .: 0.05).rvhcrcasIV did not ciiller
u'iththcothertria|s(0'08r0.0|.C.min'.P>0.05).TIrreeparticipantsconrpIainedofnunlbnesstrr.parest|resiain1heirarrll
adnrinistrationof thechilledsaline.althoughthesesymptomsresolvedr.vitliin5 rninof ceasingtheinfusion.Conclusions:All tlrreecoolins
techniquesreducedI, andwould be suitablefbr first aid applicationin a frcldscttingduringtranspoftationto adequaternedical1'acilities.
ClhilledIV salinedid not produceany contraindications.providinga suitablcaltcmativetbr I, cooling.Ke1 rbrds: tIEAT ILLNESS.
IIYPERTITERMIA.INTRAVENOUSSALINE.COOLING RATES
eatstrokcis a rncdicalcmcrgcncywith high mor-
tality and a severcmorbidity ratc in the absenceof
any irnrnediateapplicationof aggrcssivccooling
(3). The increasein body coretemperature(I,) canleadto
direct cellular damageand result in inf'lammatoryand
coagulationrcsponses,which contributcto the ultimate
rnorbidity(9,30).Becausemorbidity and rnortalityare a
function ol the degreeand duration ol the I,. elevation
(4,6,29),the primaryfocusof any heatstroketreatmentis to
reduceI to below40.0'C within 30 min (7).
Cold waterimmcrsionis clearlyvcry effcctivcin rapidly
reducing T, (10,21,26,21).In icc-cold watcr (2'C;
. t .
0.J5'Crnin
'.1,
{. cooling ratcshavc been shown to be
greaterwhen comparedwith cool water (8'C-20'C;
Addrcssfbr corcspondcnce:Wadc H. Sinclair.BSpExSc(Hons).Institute
of Sport and ExerciseScience..lar.nesCook Universitl,.Townsville.
Queensland.48I l. Australia:E-nrail:Wade.Sinclair(rr.jcu.edu.au.
Subnrittedfor publicationOctober2008.
Acceptedfbr publicationMarch 2009.
0l 95-913Ii09r.1lI | -1984i0
MEDICINE& SCIENCF,IN SPORTS& EXF,RCISE,.
C'opyright(rr2009by the AnrcricanC'ollegcof SponsMcdrcrne
DOI: I 0.l249IMSS.0b0l3c3I fila7acu2
0.19'Cmin
') (Zl). Hou,cvcr,thc supplyof a largcvolurne
of cold waterin all sporringor occupationalscttingsis rrtlt
alwayspossiblc,which would also limit thc utilizationof
ice-wettowels (0.lloC rnin ';
1t1. Water sprayingand
fanning has also bcen rcporled to be very eftbctive in
reducing[. averaging0.14'C'rnin
'
1tS,tV,ZZ,:2).A, T,
cooling rate of 0.32'C'rnin
I
has been reportedfbr a
specializedbody coolingunit (31), althoughthis ratehas
not been able to be repeatedin patientswith heatstrokc
(0.05'C'min ';
1tO1andpossiblythc mcasurcrncntsitefbr
[ (tympanic)may havcinflucnccdthc coolingratereported
by Wcincr and Khogali (3l). Howcvcr, as for water
immersion,the provisionof high-powcrcdfans lxay not
alwaysbe possiblein rernoteenvironurentsand may lirnit
the practicalityof this technique.Ice/cold packs are
commonlyusedir.rhospitalsettingsand arc rccourrncndcd
for trcatmcntof hcatinjurics(2);howcvcr,vcry low'cooling
ratcshavcbccnrcportcdforthistcchniquc(-0.03'C'rnin r).
Thcsclow coolingratcsarclikcly a rcsultof limitedcontact
bctwccnthc skinandiccandthc low hcatcapacityof small-
volurnc icc/coldpacks.Although icc/cold packs are far
morc porlablcin a ficld sctting.thc powcr rcquircdto freeze
thcscitcms is largc.
More recently,chilledsalineinfusionhasbeenshownto
be eflectivein inducinghypothenriain patientswho have
I984

2. sustainedan out-of-hospitalcardiacarrestwith an associated
periodof anoxia(5,16,20).A reccntstudyexaminingthc
uscof 0.5-to 2-L bolusdosesof 4oCsalinein cardiacarrest
patientsin a prc hospitalsettingshowcda meantempera-
ture decrcaseof 1.24'C. and thc chillcd salincwas not
associatedwith adverseirnpacton blood pressure,HR,
afterialoxygenation,pulntonarycderuaon initialchestx-ray,
or cardiacrearrcst(20). Furlhcrrore,Frankct al. (13,14)
havealsouscdchilledsalineinfusionto efl-ectivelyreduce[.
in nonr.rothermicyoung and clderly parlicipantsto cxamine
then.noregulak)ryresponsesto body core temperaturccool-
ing.Althoughcfl-ectivc,conccmsregardingthc possibilityof
cardiacarrhythmias,vcntricularflbrillation, or rnyocardial
intarctionasthemyocardiurncoolsdueto thedirectcff-ectof
thccoolsalinehavcbeenexpresscd(26.21):theprioritylnust
lay with coolingthe hypcrthennicindividual.In addition,
thc infusionof isotonicsalinewill alsoassistin restoring
hydrationstatusthattypicallyaccontpaniescxercise-inducccl
hypcrrherrnia(9.28).
Clearly.cold or ice-watcrimrncrsionarc the rnostefl'cc-
tivc modalityfbr rcducingl. in hyperlhcmicindividuals,
lvhereastreatmcnt recomrnendationsclearly suggestthe
rmplernentationof coolingmodaliticsbefbrctransportationof
aflbctcdindividuals(2I ). However,clarityovcr an appropri-
ate fleld-basedfirst aid treatmcntadministrablcen routeto
aclequaternedicalfaciliticsis yct to becstablishcd.Thercfbre,
theprirnaryobjcctiveof thecurrentstudywasto contrastthc
ellicacyol'chilledsalineinfusionagainstthc morecommon
fieldcoolingmcthodsof icepacksplacedat thebackol the
neck.groin.andaxillaeandwatcrsprayingwith lanningthat
mimicsdousingindividualswith lvaterwhile cvacuatingin
thebackof a vehiclcwith rnoderatcairflow.
METHODS
Participants
Elevenrr.ralesparlicipatcdin this stLrdywith descriptive
characteristicsprescntedin Tablc l. All participilntswcrc
hcalthy, of good fitness (Tablc l). complercdwritcn
infbnnedconsent.and were rncdicallyscreencdfor any
cardiovascular.musculoskeletal,respiratory,or thennoreg-
ulatory contraindicationsbeforeparticipatingin the study.
Both the Australian Defcnce Human ResearchEthics
Comrnitteeand JarncsCook UnivcrsityHurnanRcsearch
TABLF1 Panicipanlcharaclerjsttcs
ASe(yr)
Height(m)
Bodymass'(kg)
Sudacearea(m2)
V02,,,0"'(mLkg r.minr)
1499n.s!
23.5t 2.3
1 8 2 | 0 0 9
80.1 | 7.6
2 . 0 11 0 . 1 4
54.8: 2.5
"Bodymasswasnotsignificantlyditferentamongthethreetrialsandispresentedas
tnemeanforalltrials.
"V02,na"estimatedfromself-reportedbesttimefor a2.4-knrun(27).
EthicsCommitteeapprovedthe experimentalprotocolsand
procedurcs.
Experimental Procedures
All parlicipantscompletedthrcc standardizedexercise-
inducedheatingphasefbllowed by a 40-min treatment
consistingof one of threecoolingtechniques:intravenous
salincinfusion(lV), icepacks(lCE).or watersprayandfan
cooling(FAN). Trialswcreprcsentedin a counterbalanccd
orderandwereconductcdat the samctime of day with each
of the thrce trials separatedby 72-96 h. All trials wcre
conductedin a clinrate-controlledcharnber(34.2 t 0.5.C
ancl62.3! 3.lyo rclativchumidityandcirculatingairspeed
<0.5m.s r).
Participantswore running shocs,camouflagcdpantsand
shin, and Lycra bike shots. Thc exercise-inducedheat-
ing phaseconsistedof a walk-run (2 rnin at 6 km.h
-r
and4 min at l0 km.h r)protocol
on a motorizedtreadmill
until parlicipantsexpcrienceda 2,.> 40.C, an inability to
maintainthe workload,or the developmentof signs or
symptomsof heat-relatedillness. During the first testing
session,five participantsdid not achicve the target [.
during the excrcise-inducedheating phase bccar"rseof
physicalcxhaustion.During slrbsequcnttrials,theseflve
participantsexerciscduntil the samed. (range: 39.5.C-
39.9'C) that was attainedin the first testingsesstonto
ensure a consistentdcgree of hypcrlhermia. After the
hcatingphase.parlicipantsundertooka standardized5-min
transitionphasebefbrethe commencementof the treatment.
During thc 5-min transitionphase,participantswere
escoftedfiom the trcadmill to a sct of scaleswhere body
massmcasurementsfully clothedand in bike shofisonly
were obtained.Participantsassumeda supinc posture
(wearingbikeshortsonly).andthecoolingtechnrqueswere
applicd during a 40-min period. Thc 4O-rnin cooling
treatmcntdurationwas a rcsultof the 2-L salineinfusion
rcquiring20 25 rnin anda furtherl5 min wasallowedfor
adcquatedilutionof thecoldsalineandmeasurementof the
resultingeffbcton body coretemperaturc.The threecooling
techniquesconsistedof thc following:
lV. Participantswerc inluscd with two l-L bags of
chilled(20'C). 0.9% sodiumchloridcsolution(saline)via
a I6-gaugeperipheralintravenousline in an antccubital
vein by attcndingclinicians.The relativcvolumcof saline
infusedwas 25.5 t 2.4 ml.kg I
body lnass.tl.rcabsolute
volumc was standardizcdratherthan the rclativcvolurne
because,in a field sctting,a standardabsolutevolumc is
more practical.To replicatcclinical field procedures,the
salincbagswere retrovedfrom refrigerationapproximately
2 5 min before usc and were infused at a rate of
approximately84 ml-.rnin '.
The total infusiontlme was
23.9 ! 3.7 min with participantsremainingin the supine
positionfor theremainderof thetreatmenttime.A pilot trial
was conductedto cstin-ratethe likely tcmperatureof the
salineentcringthevein.A thermistorwasplacedat thepoint
wherc the catheterwould normally havc enteredthe vein
FIELDHYPERTHERMIATREATMENTS Medicine& Sciencein Sports& Exercise" 1985

3. with the setupandproceduresusedduringthepilot identical
to those used during the cxpcrimcntal trials. At the
representativcflow ratc, thc averagc saline temperature
reflectiveof the fluid enteringthe vein was 20'C. This
saline temperaturewas not surprisingconsideringthe
significantheatlossduring infusionas a resultof the large
surface area (thin, long tubing) and the large thennal
gradient(saline vs environment).The 2-L bolus infused
was representativeof lllVo of the averagevolume lost
duringtheheatingphaseof theIV trials(1.710.3 L).
lCE. Five resealableplasticbags(0.22 x 0.25 m; total
ice nrass: 4.9 t 0.6 kg) were filled with cornmercially
availableice cubes with one bag applied to each of the
followingpositions:left andright sidesof the participant's
groin (anterioraspect),left andright axillae,andthebackof
the neck(dorsalcerr/icalregionof the spine).The ice packs
remainedin placefor the durationof the treatment.
FAN. Participantslay supine with their head closest
(within 0.3 m) to an industrialfan (0.84-mdiameter).Once
treatmentcommenced,water storedin a pressurizedwatcr
containerwithin the chamberwas sprayedcontinuouslyfor
60 s over the participant'sentirebody (headto feetfor 30 s
and feetto headfor 30 s).Watertemperafure(-32'C) was
designedto replicatethat which is readily availablein a
field environmentand was heatedonly via the ambient
environmentwithin the climate-controlledchamber.Subse-
quent60-swatersprays(508 t 108mL) wereadministered
every5 min for a total of eight spraysduringthe treatment.
Particularcare was taken to ensuremaximal coverageof
water fbr all exposed surfaces,and all sprays were
administeredby the same researcher.The industrial t-an
ran continuouslyfor the 40-min treatmentwith airspeed
approximately8.40 m's I at the head, 7.4 m's I
at the
waist,6.30m's I
at the thigh,and3.8 m's
'
at the feetof
participants.These airspeedswere chosen becausethey
would be expectedto occurat thebackofan openor a soft-
sidedvehiclethat may be usedto evacuatecasualtiesin a
field setting.
Participantswereoffereda standardizedvolumeof water
(200 mL) of water at chambertemperatureevery 12 min
throughout the exercise-inducedheating and treatment
phases to coincide with the 2-rnin walk during the
intermittent exerciseprotocol. The time and volume of
water consumedwas documentedduring the first trial,
replicatedin all subsequenttrials and accountedlor in the
determinationof sweatrates.
Experimental Protocol
Beforeeachtrial,parlicipantsprovideda rnidstrearnurine
sample for the determinationof urine specific gravity
(USG) via a handheldrefractometer(Atago URICON-NE;
Atago Co., Ltd., Tokyo, Japan).A euhydratedstatefor all
participantswas confirrnedby USG <1.020(8). When the
initialUSG >1.020,participantsconsumed600mL of either
a flavored ilso-osmoticdrink or water before underlaking
the exercise-inducedheatingphase.Heightwasrccordedto
the nearest0.01 m using a porlablewall-rnountedstadi-
ometer(HandyHeightScale;MentoneEducationalCenter,
Melbourne,Australia).Body mass(bike shortsonly) was
rneasuredvia scalesand recordedto the nearest0.02 kg
(DlGl Compo.Wedderbum,Sydncy,Australia)beforeand
irnmediatelyafter the cxercise-inducedheating and treat-
mentphascs.
Body core temperaturewas measuredvia a telemetric
systcmcomprisingof aningestibleterlperaturepill (2 cm x
1.2-cmdiamctercoveredin a siliconerubber;HQ Inc.,
Palmetto,FL). The emitted I,. signal was receivedand
storedby a data-loggingunit (BCTM; FitSense,South-
borough, MA) situated near the parlicipant during the
exercise-inducedheatingandtrcatmcntphases.Parlicipants
ingestedthepill at least5 h beforethetrial to ensurethepill
hadpassedthe stomachwhenthey arrivedat the laboratory.
Skin temperaturesfor scapula(Isc..o,pur_,q),upper chest
(IcHesr),upperann(I.rnvuppnn),loweram (Ienvr6wEn),
and calf (Ic,4re) were recordedat 60-s interualsthrough-
out the exercise-inducedheatingand treatmentphasesvia
srnall button-shapedthennistors(ThermochroniButtons;
Maxim IntegratedProducts,Dallas.TX). Mean skin tem
perature(2,*) was calculatedusing the fbllowing modified
equationand representedthe averagcskin ternperatureof
the nontreatedregionsol the whole body:
f'r.("Cl) :0.21I51',1p111.1 + 0.2lIcrtsr * 0.07frp111 1,p111
* 0. I 2 f ,rnrrror',sR* 0.39f1 rL1,
The lr calculation was modificd from a previous
equation(18) to accountfbr possiblelocalizcdeflectsof
ICE on thigh skin temperaturemeasurementsand ft.
Sweatrate was calculatcdas the differencein body mass
and adjustmentfor fluid consulxed.HR was recordedat
60-sintenralsthroughoutthe exercise-inducedheatingand
treatmentphasesvia a telemetricHR monitor (RS800sd;
Polar ElectroOy, Kempele,Finland).In addition,ECG
electrodeswere placedon each parlicipantto monitor for
arrhythmiasduring the cooling phasc.Thc ECG electrodes
wereplacedin thefollowingpositions:manubriumandjust
below the l0th rib on both the left and right sidcsof the
trunk. ECG leads were then attachedto the electrodes
connectedto a Powerlab 4sp (ADlnstrurnents,Sydney,
Australia)via a BioAmp (ADlnstruments,Sydney,Aus-
tralia), and sampledat 1000 Hz using Charl v5 software
(ADlnstnrments,Sydney,Australia).There are numerous
anecdotalcommcntsamongphysiciansthat infusingcold
saline will directly cool the myocardium and inducc
arrhythmias;consequently,the attendingphysicianvisually
monitoredfor arrhythmiasthrougl.routthe durationof cach
IV treatmentphase.
Statistical Analyses
Data analysiswas conductedusing the StatisticalPack-
age for Social Sciences(v.l4; SPSS, Chicago, IL).
Distributionand nonnality ol datawere assessedusingthc
Kohnogorov Smimov test with a Lilliefbrs significancc
1986 OfficialJournalof theAmericanColleoeof SDortsMedicine http://www.acsm-msse.org

4. 40.5
4 0 0
"t---1..o " "
6
E a r
I
o
o 3 2
= - -
o 3 9 5
o
o
b
r o f ,
o
T '----o-
T---l
I r
I T--+-_{
r 1 1 -
-J
I
37.O
3 7 5
-s o '
,,i,'"* *ji",,"il,,,"ii
30 35 40
FICURE l-Mean :t SD core temperature at the end of exercise
(5 min), start (0 min), and during IV, lCF, and FAN cooling
techniques.'P < 0.05 versus exercise(5 min); bp < 0.05 versus start
of treatment (0 min); iP < 0.05 ICE versus FAN.
concction.Analysiswas conductedvia two-way repeated_
measuresANOVA (treatment:IV, lCE, and FAN x time).
,Repeated-measuresANOVA (between treatments)was
; conductedfor Z" rate of reduction,sweatrate, USG, and
exercisetime during the heatingphase.posr /zocanalysis
wasconductedusingTukey'sHSD test.Whereassumptions
of ANOVA werenot met,nonparametriccomparisonswere
performedvia Friedman'stest with subsequentpost hoc
analysisby Nemenyi'stest(17).o was setat 0.05,andall
valuesarc presentedas mean+ SD.
RESULTS
Before each exercise-inducedheatingphase,all partic_
ipantsexhibiteda similar USG indicativeof a euhydrated
srate(1.014+ 0.006for IV, 1.01510.007 for ICE, and
1.013t 0.009for FAN, P > 0.05)anda similarbody rnass
(80.5t 7.5 kg for IV, 19.9t j.6 kg for ICE, and 80.0r
7.7 kg for FAN, P > 0.05). The mean durationof the
exercisc-inducedheatingprotocolwas58.5+ I l.g min and
did not differbetweentrials(60.5t 13.2min for IV. 56.01
6.7min forICE,and60.5t 15.8minfor FAN,p > 0.05).In
rrddition,duringtheheatingphase,sweatratesdid not differ
betweentrials(1.1!0.3 L.h-r for IV, 1.6r 0.4 L.h I
for
lCE, and 1.5+ 0.5 L.h I
for FAN, p > 0.05).Dehydration
aftcr the heatingphasewas not significantlydifferentbe_
TABLE2. C0olingrates(.Cmin 1) fromlhe commencement0f each0ostco'lin0
treatmenlphase.
- -o-
V
- ! -
ri,l.lo*Jj",,n"il,,,"3i
30 35 40
FIGURE 2-Mean t SD skin temperature at the end of exercise
(5 min), start (0-min), and during IV, ICE, and FAN cooling
techniques.*P < 0.05lV versusFAN; ip < 0.05ICE versusFAN.
tweentreatments(P > 0.05);however,IV (-0.25 t 0.24%)
was significantlylessrhanboth ICE (1.7g t 0.l91o) and
FAN (1.41t 0.18%)afterthetrearmentphase.
Parlicipantsachieved a similar Zl. at the end of the
exercise-inducedheating phase and commencementof
treatment(Fig. l) with {. being significantlyreducedby
the 1Othmin of treatmentandremaininglower until theend
of treatment(main effect; Fig. l). During the first 10, 15,
and20 min of the treatmentperiod,the rateof Zl,reduction
was significantly greaterfor FAN when comparedwith
ICE, whereasIV did not differ from the other two trials
(Table2). At thecompletionof the40-mintreatmentperiod,
between-trialdifferenceswere not evident(Table2).
After the exercise-inducedheating phase, I.p was
approximately36.5"C, and it remainedat this level for
15 min in the IV and ICE trials, significantlydecreasing
thereafter(Fig. 2); on the otherhand,in the FAN trial, the
I,p was significantly reducedafter 5 min of treatment.
Between-trial differenceswere evident after 5 min of
-o-
V
- c
_ 5 0 5 1 0 1 5 2 0 2 5 3 0 3 5 4 (
Time of treatment(mins)
FIGURE 3-Mean I SD HR at the end of exercise (5 min), start
(0 min), and during IV, ICE, and FAN cooling techniques.+p < 0.05
IV versusFAN; tP < 0.05 ICE versus FAN; Ip < 0.05 iV versus ICE.
tcE
FAN
1 8 0
IV
tcE
FAN
+
c'F 160
E
a
a
3 140
otcE FAN
To5 min
To10min
To15min
To20 min
To25min
To30 min
To35min
To40 min
0.06I 0.02
0 07+ 0.01
0.08t 0.01
0.08r 0.01
0 0 7 t 0 0 1
0.07t 0.01
0 06r 0.01
0.061 0.01
0.04t 0.04
0.061 0.04
0.07: 003
007t 0.03
0.07r 0.02
0.07r 002
0.06I 0.01
0.061 0.01
0.07t 0 07
0.10r 0.05-
0.101 0.03-
0.091 0 02-
0.08t 0.01
0.071 0.01
0.06r 0.06
0.06r 0.01
Alltimeepochsarefromthecommencementol thetreatmentphase
- P < 0.05,FANwasgreaterthantheICElreatmentforthatperiod.
FIELDHYPERTHERMIATREATMENTS Medicine& Sciencein Sports& Exercise. 1987

5. cooling andremainedfor the entire40-min cooling period,
suchthat the ICE and IV were greaterthan FAN with no
differenccbetwcen ICE and IV. Trcatmentphase sweat
ratesduringIV (l.l t 0.5 L'h
') wcre significantlygreatcr
thanbothlCE (0.6+ 0.3 L'h
', P< 0.051andFAN (0.2+
0.2L.h
', p < o.0l).
Thc meanHR at thc endof the cxercise-induccdheating
phase rvas sirnilar bctween trials and was significantly
rcduced during the 40-min treatlncntacrossall trials
(Fig. 3). Treatmentresultedin a significantlyreduccdHR
after 5 rnin with the mean treatmentHR for IV (I 15 t
26 beats'min
'
; being s.ignificantlygreaterthan both ICE
(108 t 32 bcats'min
', P < 0.01) and FAN (105 I
33 beats'rnin
', P < 0.01). Thc greaterHR for lV compared
with FAN was evident after 5 rnin, whereasdiff-erenccs
betweenIV and ICE,werc not evidentuntil aficr 30 min of
trcatment(Fig.3).
No abnormalcardiacrhythrnswere obsen'rcdduring the
adn-rinistrationof the chilled IV salinc.Only threeparlic-
ipantscomplaincdof cold sensationduring IV intusion'
One of thcsepar-ticipantsreporlcdnumbnessanda tingling
sensationdown thc infuscdarm, whereasanothcrreported
f-cclrngcold up to the axilla duringthe first infusedbagand
substantiallylessduring thc second.The third participant
also felt tingling,which thc attendingcliniciansuggestcd
was rnedial newe paresthcsia,and was supportcdby its
dernisconcethc intravcnousline wasremoved.
DISCUSSION
The current study has demonstratedthat in cxerclsL'-
indr-rcedhyperlhcrmicpafticipants,thc threecoolingtech-
niques all initiated a rcduction in I. suitable fbr f-rrst
aid applicationin a fleld setting,althoughthey were con-
sidcrably lcss than those cooling rates rcpofied fbr cold
water immcrsion(10,2|,26,21).McDermottct al. (21)
recentlysuggcstedthat cooling ratcs betwcen0.08 and
0.15'C'rnin
' areacccptablcin the tl'eahnentof EHS.Thc
threc cooling techniquesinduced sirnilar I, rcsponscs
acrossthe 40 rnin of treatt.nent,although the FAN was
significantly more effcctive in reducing I in the first
20 min of coolingwhcn comparedwith thc ICE. Caution
shouldbe extcndedto anyapplicationofthc cunentrcsults
to individualswith thennoregulatorydysfunction.ln addi-
tion, isotonicIV infusionshouldonly be adrninistercdto
hyperlhcrmicanddehydratedindividualsandshouldnot be
considercdfbr individuals that are hypcrhydratedand/or
hyponatrernic.
Previously,Frank et al. (13) infused30 rnl'kg
I ol'
chilled(4'C) salinein normothcrmicparticipantsduringa
30-minperiodandinduceda coolingrateof 0.04'C'rnin
'.
In the current study, the grcater cooling rate of
0.08'C'min-r could be attributcdto the elevatedswcat/
evaporativcrate. Applying the thetmodynamicprinciplcs.
the additionof 2 L of 20'C salincto an 80-kg individual
with a I., of 40.0'C would reduccI by 0.05'C to 39.5'C.
During the chilled saline infusion period, the rnean [.
reductionwas 1.6oC,resulting in an additional I'l'C
reductionthan that attributableto thc themodilution of the
IV infusion.Given thatthe evaporationof I g of sweatwill
resultin 2.43kJ of hcatbeinglostfiorn thebody.only onc
third of the sweatproduced(-367 mL) would needto bc
cvaporatcdto accountfor the LloC reduction.Conscquently,
rnr.rchof the heat lost in the lV trial may have bccn at-
tributedto the naturalsweatevaporation.In rcmotescttlngs,
whcre sufficientpower to produceice and opcratea large
f-anis not available.portablefiidges that operateon l2-V
directcurrcntcanbe usedto providechillcdsaline.
Theratcof I,. reductionfbr thc lCE,trial (0.07"C'rninr)
was much greatcr than that previously reportcd
(-0.03'C'min ') (tg) and n-rayref'lectdifferenccsin icc
pack "type" appliedto the back of thc neck,axillae,and
groin. Kielblock et al. (19) used cornmerciallyavailablc
instantcoldpacks,whereasice cubesin a plasticbagwcre
used in the presentstudy. Cornparedwith large rigid ice/
cold packs,the melting of ice cubesmay have induccd
greaterskincontactwith watcrof very low tempcratureand'
conscquently.a greaterrateof peripheralcoolingfbr ICE...
Furlher,a greaterICE coolingrateuay be possibleearlicr'
in the treatmentperiod if srnall amountsof watcr were
addedto the icc bagsto tnaxiurizcthe skin coverageat the
initiationof cooling.Thc high rateof hcat lossrnay also
rcflectnatr,rralheatlossvia evapclration.If onethird of the
swcat produced during thc treatmentwas evaporatc-d
(-130 mL). this would accountfor ncarly 50u,/uof the
obserr,'cdreductionin d. It is plausiblethat thc largeicc
packscontainingwaterresr.rltedin greatcrconductiveheat
loss"which.whencornbinedwith thc observcdsweatratcs
andsubsequcntevaporativecooling,rcsultedin the grcatcr
rateof obserr,rcdheatloss.
Thc cooling rate for FAN in thc prescnt study
(0.1O'C'rnin'; was sir.nilarto that prcviously reporlcd
undersimilarenvironmentalconditionsduring fan cooling
(0.020.l2oC'min
') (t t,ZZ.:z)and helicopterdowndraft
(0.10'Crnin ') (25).The currcnttechniqueof rcgularly
wettingtheskinwith wann waterandhighairflowseelnsto
inducea substantialheatlossin a hot-humidenvirontnento
whcrethe watervaporpressuregradientis lcssf-avorable:'
Wciner and Khogali(31) rcporteda rnuchhighercooling
rate (0.32"Cmin
r)
using spccificallydesignedcooling
units;howevcr, I,. was assesscdvia tynrpanicthern.romctry
andthis reporledratcof cooling may be morc reflectivcof
circulatingairflow ratherthan the coolingtechnique(23).
The potentialcxplanationfor the variationsin rcporledratcs
of I,. rcductionrnaybc variationsin air speed,tcmperaturc.
duration,volume,andpositionof watcrapplicdduringthe
coolingprocess.For examplc.thecontinuousapplicationol
30.5'C waterand comprcssedair'(0.06rns
'1
eliciteda
greatcrcooling rate (0.12'C'min
'; than a single 3-min
applicationwithout air (0.09'Cmin r; in hyperplexic
individuals(32). Howevcr,applyingwatcr lnist intermrt-
tently to the anterior and posterior exposedsurfacesof
1988 OfficialJournalof the AmericanCollegeof SportsMedicine http://www.acsm-msse.org

6. participantsonly eliciteda 2.,coolingrateof 0.03.C.min-l
for individualsheatedduringintermittentanaerobicexercise
(22). Collectively,theseresultsand thosefrom the present
study suggestthe continuous application of water over
exposedsurfacesmay elicit a greatercooling response.In
the eventthata power supplyis unavailableto supporla fan
in a field setting,wetting individuals being evacuatedto
emergencyrelief in open-airvehicleshas elicited coolins
ratesup to 0.l4.C.min I (16).
The FAN also induceda largereductionin I.k as water
sprayedon to participantswasevaporated.This reducedI,p
rsproposedasthe likely causefor the dramaticreductionin
sweatratein the FAN trial when comparedwith the IV trial
(12,21).Sweatingwas alsosuppressedin the ICE trial, and
it is alsosuggestedthatthe dramaticreductionin local skin
temperaturesunder the ice packs induced a reduced
thermoregulatorydrive for sweating(12,24). When a fan
is usedto reduce71,it is extremelyimportantthatwater is
regularlyaddedto the skin to ensurecontinuedevaporatlve
heat losses.Spraying water at ambient temperaturewill
rnaintaina high 7lp,therebylesseningthe thermalgradient
'between the skin surface and surroundingair boundary
(22.31,32).Consequently,this would limit vasoconstriction
and promoteheattransferencefiom the body's core to the
skinfor dissipation(3l). Collectively,theobservedcooling
ratefor the FAN trial andthe correspondingI.1.responsein
the current study was encouragingconsideringthe high
hurnidity.
In conclusion,whereasicedor cold waterimmersionis
substantiallymore effectivein reducingbody core temper_
ature than the currently examined treatments,ln remote
settingswherethis temperatureand volume of wateris not
available,the currenttechniqueswould be an effectivefirst
aid treatmentof hyperthermicindividualsduring transpor_
tatronto aptly equippedmedicalfacilities.Considerinsthat
REFERENCES
l. Armstrong LE, Crago AE, Adams R, Roberls WO. Maresh CM.
Whole-body cooling of hyperthermic runners:comparison of fwo
lield therapies.Am J Emcry tr'tett.-996.1414;:J55-g.
2. Austrafian Resuscitation Council. Heat Inducetl Illness (H1,per-
thermia): First Aid Managentent.Melboume: Australian Resusci_
tationCouncil; 2001.2 p.
3. Bouchama A, Dehbi M, Chaves-CarballoE. Cooling and hemo_
dynamic management in heatstroke:practical recommendations.
Crit Care. 2007,I I (3):R54.
:1. Bouchar.naA, Roberts G, Al Mohanna F, et al. Inflammatory,
her.nostatic.and clinical changesin a baboon experimentalmodel
for hcarsrroke.J App! Ph.v.sittt.2005:9g(2'1:697705.
5. Bruel C. Parienti J-J, Mane W, et al. Mild hypothermia during
advanced life support: a preliminary study in out_of_hospital
cardiacarrest.Crit Care. 200ii;12(l):R3l.
6. Buckley IK. A light and electron microscopc study of thermally
injured cultured cells. Lab Intest. 1972;26(2):201 9.
7. Bynurr GD, Pandolf KB, Schuette WH, et al. lnduced hyper_
thcnnia in sedated humans and the concept of critical thermal
maximum. Am J Physiot Regul Integr Comp phtsiot. l97g;
235(s):R228-36.
the threecooling methodsusedin the currentinvestigation
rely on threedifferentmodesof heatloss,namely,dilution.
conduction, and evaporation,the combination of thcse
techniquesis likely to inducegreaterratesof cooling and
warrants further investigation.Furlhermore,becauseno
adverse symptoms were exhibited during the IV trial.
chilled salineinfusion may presentan effectivcaltemativc
for 71.cooling of exercise-inducedhyperthenniain rernotc
locationswhereothercoolingtechniquesarenot available.
WHAT IS ALREADYKNOWNABOUT
THISSUBJECT
r Iced or cold water immersion is the rnost eff-ective
meansof rapidly reducingbody core ternperaturcin
hyperthermicindividuals
WHATTHISSTUDYADDS
o Intermittentwatersprayingwith continuousfan cooling
is effectivein rapidlyreducingbody coreternpcrarure
o A 2-L bolusof chilledintravenoussalinesolutionis
effectivein reducingbody core temperaturcin hypcr_
thermicindividuals
o Rapidbodycorecoolingvia chilledsalineinfusiondid
not seemto resultin any significantcontraindications
suchas cardiacarrhythmia
FundingforthisresearchwasreceivedfromtheCommonwealth
ofAustralia.
^ Theauthorsacknowledgetheassistanceof MelissaCrowe,Krm
Chivers,RikkiAnderson,andEmmaparker.Theopinionsexpressed
inthisarticlearethoseoftheauthorsanddo notrefrecttheofficial
policyor positionof the Departmentof Defenceor theAustralian
Government.Thefindingsof the presentstudydo not constitute
endorsementbyACSM.
8. Casa DJ, Amstrong LE, Hillman SK. et al. National Athletic
Trainer's Association Position Stalement: f'luid rcplaccment lor
athletes.J Athl Train. 2000:35e1:212,24.
9. Casa DJ, Maresh CM. Armstrong LE, et al. lntravqnous versus
oral rehydration during a brief perioci: responsesto subsecluent
exercisein the heat.Med SciSport E.rert,.2000;32(l):124-13.
10. Casa DJ, McDermott BP, Lee EC, yeargin SW. Armstrong LE.
Maresh ClM. Cold water imntersion: the gold stanclarcl lbr
exertional heatstroke treatment. Exerc Spon St.i Ra,. 2007;
35(5):l4l-9.
ll. Clapp AJ, Bishop PA, Muir I, Walker JL. Rapictcooling
techniques in joggers experiencing heat strain. J St.ilvlett Spor.t.
2001l,4(2):l60-j .
12. Cotter JD, Taylor NAS. Thc distribution of cutaneoussucrotrroror
and alliesthesialthennosensitivity in rnildly heat_stresscdhumans:
an open-loopapproach.J Pht,siol.2005;565(prl):335 ,15.
13. Frank SM, Higgins MS, Fleisher LA, Sitzmann JV. Raff H.
Breslow MJ. Adrenergic, respiratory,and cardiovascularefl.cctsof
core cooling in humans.Am J pht,sbl RegulInregr Comp pht.siol.
1997:272121:R55702.
14. Frank SM, Raja SN. Bulcao C. Goldstein DS. Aee_rclated
FIELDHYPERTHERMIATREATMENTS Medicine& Sciencein Sports& Exercise,, l9lt9

7. 19. Kiclblock AJ. Van RcnsburgJP. Franz RM Body cooling as a
rnetlrodof rcclucinghyperthennra.S Ali Metl J' l9tt6r69(6):378-U0'
20. Kim F. OlsLrlkaM. CarlbonrD' ct al. Pilot studyof rapid infusion
of 2 L of ,1'C norrral saline fbr induction of mild hypotherrniairr
hospitalizecl.comatosc sun'ivors of out-of-hospital cardiac arcst'
Cirtttlatitttr.2005:l l2(5):715 9.
21. McDcrnrott flP. Casa DJ, Ganio MS' et al Acute wholc-body
cooling for excrcisc-induccdhyperlhernria:a systetrtaticter ierv'
J .|rhl Truin. 2009:4;l(I ):8'l 91.
22. Mitchell JB. Schillcr ER. Miller JR. Dugas JP The influenccof'
diflercnt externalcooling rnetht'dson thenltorcgulrtotyresponses
bclorc and after inlensc intermittont cxercise in the heat'
.l StrengrhContl Res.200l;15(2):24754'
26.
Moran DS, Mendal L. Core temperaturefileasursment:mcthods
and cuncnt insights.SportsMed 2002;32(14):87985'
Patterson MJ, Cotter JD, Taylor NAS Hun-ran sudomotor
responses to hcating and cooling upper-body skin surfaces:
cutaneousthcrmal sensitivity A(:ta Pht'siol Scand' 1998;163(3):
289 96.
PoultonTJ, Walker RA. Helicoptercooling of heatstrokevtctttns'
{tia| Spote Ent,ironMed. l98l;58(1):358-6I'
Proulx Cl, Duchatme MB, Kenny GP. Effect of water tcmpcrature
on cooling efficiency during hypertherrnia in hunans J Appl
Pht',siol. 2003;94(zl):I3I7-23
27. ProulxCl, DucharmeMB, KennyGP Saf'ecoolinglimits lrotr
exercise-inducedhyper-thcrmia-Eur J Appl Physiol'2006;96(4):
43145.
Pync S. Intravenousfluids post marathon: when and why'l Sporl'r
Med. 2007:31(4-5):434-6.
Shapiro Y. Rosenthal T, Sohar E. Experimental heat-stroke: a
nrodelin clogs.lrcft Intern Med.1973:l3l(5):688 92
Shibolet S. toll R, Gilat T. Heatstroke: its clinical picture and
nrechanismin 36 cases.Q J Metl.1967;36(144):525-'18'
Weiner JS, Klogali M. A physiologicalbody-cooling unit fbr
trcatmentof hcat strokc.LLtntet.|980'j|5(8I67):507-9
Wyndham CH, Strydom NB' Cookc HM, ct al' Methods of
cooling subjectswith hyperpyrexia.J Appl Phvsiol' 1959;14(5):
7 7 t 6 .
1 5 .
thcmoregulatory diffcrencesduring core cooling in humans liit '/
Pln'siol iegrtl Intcgr Conp Ph.t'siol.2000:279(l):R349 54'
HacladE. Moran DS. Epstein Y. Cooling hcat strokc patientsby
available field t.tleasurcs.Intensitc C'trre llletl 2004;30(2):338'
Lladad E. Rav-Acha M. Hcled Y. Epstt'rnY' Moran DS Heat
strokc:a rcvieu'of coolingrlethods. SptttlsMed' 200434(8):50l-l l'
Hatch E. Lazarirton A. |'he Reseurth Munuul Design and
"lrrrtisllc'.s/bt Appliett Lingtrisrits. floston (MA): tleinle & Heinle
PLrhli.lrer.:l9u 1. n. .1556.r.
Intenrational StanclarclsOrganisation. ISO 9886' 2001(L-) Ergr
ttomic.s- Evtltrutiott of'Thermul Strain h.t'Ph.t'siologiculMeasure'
iircrrts.Cencva (Switzerland):ISO: 2004 15 p'
23
21
25
l o .
t 1
I U .
28
29
10.
3 t
32
1990 OfficialJournalof theAmericanCollegeof SporlsMedicine http://www.acsm-msse.org