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ARTICLE IN PRESSESUS-3107; No. of Pages 8

esuscitation (2007) xxx, xxx—xxx

LINICAL PAPER

old infusions alone are effective for induction ofherapeutic hypothermia but do not keepatients cool after cardiac arrest�

ndreas Kliegela, Andreas Janataa, Cosima Wandallera, Thomas Uraya,lexander Spielb, Heidrun Loserta, Matthias Kliegel c, Michael Holzera,oritz Haugka, Fritz Sterza,∗, Anton N. Laggnera

Department of Emergency Medicine, Medical University Vienna,ahringer Gurtel 18-20/6D, 1090 Vienna, AustriaDepartment of Clinical Pharmacology, Medical University, Vienna, AustriaDepartment of Psychology, University of Zurich, Zurich, Switzerland

eceived 13 July 2006; received in revised form 17 August 2006; accepted 29 August 2006

KEYWORDSCardiac arrest;Cardiopulmonaryresuscitation;Post-resuscitationperiod;Hypothermia

SummaryAim of the study: Cold infusions have proved to be effective for induction oftherapeutic hypothermia after cardiac arrest but so far have not been used forhypothermia maintenance. This study investigates if hypothermia can be inducedand maintained by repetitive infusions of cold fluids and muscle relaxants.Material and methods: Patients were eligible, if they had a cardiac arrest of pre-sumed cardiac origin and no clinical signs of pulmonary oedema or severely reducedleft ventricular function. Rocuronium (0.5 mg/kg bolus, 0.5 mg/kg/h for mainte-nance) and crystalloids (30 ml/kg/30 min for induction, 10 ml/kg every 6 h for 24 hmaintenance) were administered via large bore peripheral venous cannulae. Ifpatients failed to reach 33 ± 1 ◦C bladder temperature within 60 min, endovascularcooling was applied.Results: Twenty patients with a mean age of 57 (±15) years and mean body massindex of 27 (±4) kg/m2 were included (14 males). Mean temperature at initiationof cooling (median 27 (IQR 16; 87) min after admission) was 35.4 (±0.9) ◦C. In 13patients (65%) the target temperature was reached within 60 min, 7 patients (35%)

Please cite this article in press as: Kliegel A, et ation of therapeutic hypothermia but do not keep patiedoi:10.1016/j.resuscitation.2006.08.023

failed to reach the target temperature. Maintaining the target temperature waspossible in three (15%) patients and no adverse events were observed.Conclusion: Cold infusionsarrest, but for maintenanccases.© 2006 Elsevier Ireland Ltd

� A Spanish translated version of the summary of this article appea0.1016/j.resuscitation.2006.08.023.∗ Corresponding author. Tel.: +43 1 40400 1964/1952; fax: +43 1 40

E-mail address: fritz.sterz@meduniwien.ac.at (F. Sterz).

300-9572/$ — see front matter © 2006 Elsevier Ireland Ltd. All rightoi:10.1016/j.resuscitation.2006.08.023

l., Cold infusions alone are effective for induc-nts cool after cardiac arrest, Resuscitation (2007),

are effective for induction of hypothermia after cardiace additional cooling techniques are necessary in most

. All rights reserved.

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ARTICLERESUS-3107; No. of Pages 8

2

Introduction

Mild hypothermia improves survival and neurologi-cal outcome after out-of-hospital cardiac arrest.1—3

According to the results of two large randomisedcontrolled trials the European Resuscitation Coun-cil Guidelines 2005 recommend treating comatosesurvivors of out-of-hospital cardiac arrest due toa shockable rhythm with mild hypothermia for12—24 h.4 The ideal method for induction and main-tenance of therapeutic hypothermia is not known.As experimental results suggest that the effectof hypothermia on neurological outcome might bemost beneficial when applied as early as possibleafter return of spontaneous circulation5,6 recentresearch focused on methods for fast inductionof hypothermia.7—13 So far, five feasibility tri-als have investigated the efficacy and safety oflarge volume infusions of cold infusions in morethan 200 adult cardiac arrest survivors (9—13).Those studies showed that hypothermia could beinduced very effectively with cooling rates upto −4.0 ◦C/h and no clinically relevant adverseeffects of the infusions, especially no pulmonaryoedema, were observed. Although the target tem-perature (32—34 ◦C) could be reached in mostpatients, hypothermia was then maintained byadditional more resource demanding cooling tech-niques. To our knowledge no study has investigated,if hypothermia can be induced and also maintainedby repetitive infusions of cold crystalloid fluids andcomplete muscle relaxation with deep sedation.

Methods

This was a prospective, observational case seriesof a convenience sample of patients after car-diac arrest admitted to an emergency departmentof a tertiary care hospital between October 2005and February 2006. The study procedures wereapproved by the responsible committee on humanexperimentation. According to our study proto-col there was no need for patient’s consent tobe included in our study but patients or theirrelatives received detailed information about thetrial.

Inclusion and exclusion criteria are presentedin Table 1. As with previous feasibility trials atotal of 20 participating patients was considered tobe sufficient. Data documentation was performedaccording to Utstein Style.14 Cardiac arrest data

Please cite this article in press as: Kliegel A, et ation of therapeutic hypothermia but do not keep patiedoi:10.1016/j.resuscitation.2006.08.023

of out-of-hospital cardiac arrests were obtainedthrough interviews with the ambulance physicians,paramedics, bystanders and families. The intervalfrom the time of collapse to the first sustained

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PRESSA. Kliegel et al.

erfusing rhythm was termed time to return ofpontaneous circulation. Acute care included basicnd advanced cardiac life support performed by thembulance service personnel or in-hospital emer-ency physicians per standard protocol accordingo current guidelines.4,15

At the emergency department, after initial neu-ological evaluation, assessment of respiratory andaemodynamic function, patients received the fol-owing standardised treatment. Foley cathetersith incorporated temperature probes, arterialatheters, central venous catheters, intubation andechanical ventilation were used. Sedation and

nalgesia with midazolam (0.2—0.25 mg/kg/h) andentanyl (0.01 mg/kg/h) was given to facilitate res-iratory management, to avoid stress induced bynvasive procedures and to allow continuous muscleelaxation.

tudy interventions (also see Figure 1)

euromuscular blockade was induced by rocuro-ium with a bolus infusion (0.5 mg/kg) and aubsequent continuous infusion (0.5 mg/kg/h) torevent shivering until patients reached normoth-rmia again. If patients showed any signs ofhivering or gooseflesh the dose of muscle relax-tion was gradually increased until these symptomseased. The target temperature was monitored viabladder temperature probe.As soon as patients were included they received

n intravenous bolus infusion of 30 ml/kg crystal-oid fluid at 4 ◦C over 30 min via two peripheralubital large bore intravenous catheters. Usu-lly normal saline or lactated Ringer’s solutionas selected, depending on serum electrolytes

evealed in the first blood gas analysis on admis-ion. If no laboratory values were available normalaline was used. Central venous application wasot used to avoid any delay and to reduce theisk of arrhythmias. If the temperature droppedelow 33 ◦C or clinical signs of pulmonary oedemamerged the infusion was stopped. Further man-gement of therapeutic hypothermia with colduids and/or other cooling techniques after theolus infusion is presented in Figure 1. This cool-ng procedure differed from our clinical routine,here comatose cardiac arrest survivors receiveold fluids (30 ml/kg/30 min) immediately afterdmission for the induction of hypothermia andn additional cooling technique (e.g. endovascularr surface cooling devices) is applied simultane-

l., Cold infusions alone are effective for induc-nts cool after cardiac arrest, Resuscitation (2007),

usly if it does not delay immediate coronaryngiography.

To avoid fluid overload, repetition of cold infu-ions was limited to every 6 h and the dose was

ARTICLE IN PRESSRESUS-3107; No. of Pages 8

Cold infusions do not keep patients cool after cardiac arrest 3

Table 1 Inclusion and exclusion criteria

Inclusion criteriaAge 18—85Witnessed, normothermic cardiac arrest of presumed cardiac aetiologyReturn of spontaneous circulation with systolic blood pressure >90 within 60 min of initiation of advanced cardiac

life supportComatose upon enrollment (Glasgow Coma Scale <8)

Exclusion criteriaClinical signs of pulmonary oedemaSeverely reduced left ventricular functionComa possibly due to cerebrovascular accident or head traumaPatients receiving any form of renal replacement therapyPatients with a diagnosed terminal illnessPatients with known hypersensitivity to any of the drugs used

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Known coagulopathy or thrombocytopeniaPossible pregnancy (females <50 years were tested fo

educed to 10 ml/kg for the additional applications.f possible, the target temperature was maintained

Please cite this article in press as: Kliegel A, et ation of therapeutic hypothermia but do not keep patiedoi:10.1016/j.resuscitation.2006.08.023

or 24 h with cold infusions. If the temperature rosebove 34 ◦C after 12 or more hours no additionalooling technique was applied as current guidelinesecommend a cooling period of 12—24 h.4

Tbwt

Figure 1 Treatment algorithm after inclusion. CVP: centr

gnancy)

onitoring

l., Cold infusions alone are effective for induc-nts cool after cardiac arrest, Resuscitation (2007),

emperature was monitored continuously in theladder. For cardiovascular monitoring, cathetersere placed in the radial or femoral artery and

he upper vena cava as soon as possible. Arterial

al venous pressure, FiO2: fraction of inspired oxygen.

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4

(ABP) and central venous pressure (CVP) were dis-played on a multichannel monitor (HP Series 600Monitor, Hewlett-Packard, Palo Alto, CA, USA). Spe-cial attention was paid to potential adverse effectsof hypothermia and fluid overload such as abnormalbleeding, haemodynamic instability, arrhythmias,electrolyte disturbances and signs of acute heartfailure.

If the patient’s core temperature droppedbelow the target temperature (33 ± 1 ◦C) we pro-vided a light weight mattress with tiny holeswith constant warm air flow (Bair Hugger®,Augustin Medical, Inc., Eden Prairie, MN) forwarming. If these methods failed to rewarmthe patient effectively, they could be rewarmedwith an endovascular heat exchange catheter(Icy catheter, CoolGard 3000, Alsius, Irvine, CA,USA).

Outcome measurements

The primary endpoint was the achievement ofthe target temperature 60 min after start of thefirst bolus infusion and maintenance of hypother-mia over 24 h. As a secondary only descriptiveendpoint, survival to discharge and neurologi-cal outcome were assessed and are reported interms of cerebral performance categories (CPC).16

The best CPC score achieved between 3 days

Please cite this article in press as: Kliegel A, et ation of therapeutic hypothermia but do not keep patiedoi:10.1016/j.resuscitation.2006.08.023

and within 6 months was used for calcula-tion. A CPC score of 1 or 2 was considered asgood, and a score of 3—5 as poor neurologicaloutcome.

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Table 2 Demographic and cardiac arrest data

Age (years)Male, n (%)Body mass index (kg/m2)Body surface area (m2)Time from collapse until ROSC (min)BLS, n (%)

First recorded ECG rhythmVF or VT, n (%)PEA, n (%)Asystole, n (%)

Cardiac arrest due to cardiac cause, n (%)Defibrillations (n)Amount of adrenaline (epinephrine) during CPR (mg)Serum lactate on admission (mmol/l)pH-value on admission

Data are given as numbers (percentages) and mean values (± standbasic life support; ECG: electrocardiography; VF: ventricular fibrilactivity; CPR: cardiopulmonary resuscitation.

PRESSA. Kliegel et al.

tatistical analysis

ata were tested for normal distribution usinghe Kolmogorov—Smirnov test. Parametric data areresented as mean and standard deviation, non-arametric data are presented as median andnterquartile range (IQR). For comparison of pre-nd post-infusion values parametric data wereested using paired t-tests. Non-normally dis-ributed variables were analysed using Chi-squarer Mann—Whitney-U-tests, respectively. p-Valuesere two-tailed, and values of p < 0.05 were con-

idered significant. All statistical analyses wereerformed using SPSS 11.5 for Windows.

esults

he demographics and cardiac arrest data of the0 patients studied are presented in Table 2. Blad-er temperature on admission was 35.2 (±1.1) ◦C.total amount of 2465 (±536) ml of cold infusionsas given commencing 93 (±62) min after returnf spontaneous circulation and 27 (16; 87) minfter admission. Cold infusions were started at aean patient temperature of 35.4 (±0.9) ◦C whichropped to 34.4 (±1.1) ◦C after 30 min (p < 0.001)nd to 34.2 (±1.0) ◦C after 60 min (p < 0.001),espectively (Figure 2).

l., Cold infusions alone are effective for induc-nts cool after cardiac arrest, Resuscitation (2007),

Of all 20 patients, 13 (65%) reached the targetemperature within the required 60 min in a meanime of 30 (±16) min. The other seven patients35%) received additional endovascular cooling 1 h

57 (±15)14 (70%)27 (±4)1.93 (±0.22)20 (±9)8 (40%)

14 (70)2 (10)4 (20)

15 (75%)2 (±1.5)1.9 (±1.6)9.4 (±5.6)7.20 (±0.21)

ard deviation). ROSC: return of spontaneous circulation; BLS:lation; VT: ventricular tachycardia; PEA: pulseless electrical

ARTICLE INRESUS-3107; No. of Pages 8

Cold infusions do not keep patients cool after cardiac a

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igure 2 Temperature course within 60 min after thetart of the first bolus infusion (n = 33).

fter start of the initial bolus infusion. Of those 13atients who had reached the target temperaturepatients (69%, i.e. 45% of all patients) required

dditional endovascular cooling for hypothermiaaintenance as their temperature increased to

34 ◦C 199 (±72) min after start of infusions. Innly three patients (23% of those who had reachedhe target temperature, i.e. 15% of all patients)ould the target temperature be maintained suc-essfully by cold infusions, sedation and muscleelaxation (Figure 3). Of those three patients, onlyne received an additional cold infusion 10 h afternclusion. One patient who had disseminated breastancer (which had not been known by the investi-ators at the time of the inclusion) died 5 h afterhe start of cooling.

There was a trend towards a higher probabilityf cooling success with cold infusions in youngeratients (54 years versus 65 years, p = 0.06) and foratients with a lower body mass index (26 kg/m2

ersus 29 kg/m2, p = 0.08) whereas body surfacerea (1.90 m2 versus 1.99 m2, p = 0.38) seemed toave no influence.

Please cite this article in press as: Kliegel A, et ation of therapeutic hypothermia but do not keep patiedoi:10.1016/j.resuscitation.2006.08.023

The total infusion amount could be given with-ut complications in all cases. No patient developedlinical signs of pulmonary oedema and haemo-ynamic measurements, oxygenation and other

lcap

Table 3 Haemodynamic, respiratory and laboratory data b

Before cold infu

Mean arterial pressure (mmHg) 75 (±18)Heart rate (min−1) 93 (±27)Sodium (mmol/l) 137 (±5)Potassium (mmol/l) 3.9 (±0.6)Haemoglobin (g/dl) 12.6 (±2.5)Platelet count (G/l) 207 (±62)PaO2/FiO2 (mmHg) 511 (± 343)

Data are given as mean values (± standard deviation); PaO2: partialoxygen.

PRESSrrest 5

aboratory variables showed no relevant changesuring and after cold infusions (Table 3).

Of all patients, eight (40%) survived to dis-harge (seven of those had ventricular fibrillations first recorded ECG rhythm) and seven (35%) hadfavourable neurological outcome (six of those

ad ventricular fibrillation as first recorded ECGhythm).

iscussion

n most patients who achieve return of sponta-eous circulation after cardiac arrest hypothermiaan be successfully induced by cold infusions.lthough large amounts of fluid were administeredithin 30 min, no serious side effects occurred.nce the target temperature was reached fewatients remained within the temperature range of2—34 ◦C but the majority rewarmed within severalours and required additional endovascular cooling.o patient required active rewarming during the

nduction or maintenance period as temperatureever dropped below 32 ◦C.

Our study is the first to investigate if patientsho are treated with therapeutic hypothermiafter cardiac arrest can be kept in mild hypother-ia by repeated administrations of cold infusions,

edation and complete muscle relaxation. To avoidardiac decompensation due to fluid overload, theolume of the 2nd, 3rd or 4th infusion was reducedo 10 ml/kg and repetitive cold infusions werellowed only every 6 h (Figure 1). Therefore, weo not know if continuous cold infusions or largerolumes of repeated cold infusions within shorterime intervals might be more effective for mainte-ance of mild hypothermia. According to our formerxperience11 a slow infusion rate of cold fluids

l., Cold infusions alone are effective for induc-nts cool after cardiac arrest, Resuscitation (2007),

eads to less effective cooling. If the combination ofheap and easy applicable cooling techniques suchs cold fluids followed by external cooling with iceacks or fans would be sufficient for hypothermia

efore and after the first bolus infusion

sion After cold infusion p-Value

81 (±19) 0.0887 (±23) 0.02

137 (±4) 0.533.9 (±0.6) 0.87

11.8 (2.2) 0.04191 (±50) 0.22352 (±166) 0.09

pressure of oxygen in arterial blood; FiO2: fraction of inspired

ARTICLE IN PRESSRESUS-3107; No. of Pages 8

6 A. Kliegel et al.

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Figure 3 Number of patients within the target temperatuand muscle relaxation.

induction and maintenance, this might save costs

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compared to the use of cooling devices. This matterhas still to be investigated.

Previous studies have already reported theeffectiveness of cold infusions for induction of

rsa2

nge (32—34 ◦C) treated only with cold infusions, sedation

ypothermia.9—13 Those studies reported cooling

l., Cold infusions alone are effective for induc-nts cool after cardiac arrest, Resuscitation (2007),

ates between 2.2 and 4.0 ◦C/h but in some casesimultaneous additional cooling techniques werepplied.11,12 We achieved a cooling rate of only◦C/h during the active cooling period, although

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old infusions do not keep patients cool after cardi

e left the patient uncovered, turned off all heat-ng equipment in ventilators and beds, and thenfusion bags were stored at 4 ◦C until just beforehe fluid was given. The reason why our coolingate was less than the previously reported is notlear. Similar to previously reported data,9—11 notll of our patients reached the target temperatureoon after the infusion, but nevertheless at 60 min5% (n = 13) had reached a temperature below4 ◦C. Patients with a lower body mass index andounger patients were more likely to reach targetemperature.

After the induction of hypothermia with coldnfusions all previous studies9—13 used additionalooling techniques for maintenance of hypother-ia. Kim et al.13 reported that some patientsho received no active cooling for maintenancead a rapid rise in temperature after success-ul induction. In contrast to our patients theseatients received only sedation with midazolamut no muscle relaxants. This anaesthesia man-gement probably has influenced the temperatureourse as shivering contributes considerably toewarming in hypothermic patients. To excludehivering all our patients received continuoususcle relaxation. However, 77% (n = 10) of ouratients who initially had reached target temper-ture after the first cold infusion rewarmed within99 (±72) min after start of infusions and neededurther active cooling by endovascular cooling. Onlyhree patients (23% of those who had reachedarget temperature) remained in mild hypother-ia. These data suggest that sedation and muscle

elaxation is not enough to prevent rewarminguring therapeutic hypothermia and that otherechanisms, such as non-shivering thermogenesis,ight contribute substantially to the rewarmingrocess.

Other previous studies have not revealed anyerious side effects of cold infusions9—13 especiallyulmonary oedema and only slight increases of cen-ral venous pressures were reported. In our patientse did not observe infusion or cooling related sideffects either (Table 3).

onclusion

n the majority of patients after cardiac arrest,herapeutic hypothermia can be induced by rapidnfusion of cold fluids. However, most patientsewarm after 3—4 h and require additional cooling.

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s most therapeutic and diagnostic interventionsan be performed within this period (e.g. coronaryngiography or computed tomography) the induc-ion of hypothermia with cold infusions will allow

1

PRESSrrest 7

rapid induction of hypothermia in this first crit-cal phase after the arrest while more resourceemanding cooling procedures can be appliedfterwards.

onflict of interest statement

here are no conflicts of interest.

eferences

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2. The Hypothermia After Cardiac Arrest Study Group. Mildtherapeutic hypothermia to improve the neurologic outcomeafter cardiac arrest. N Engl J Med 2002;346:549—56.

3. Holzer M, Bernard SA, Hachimi-Idrissi S, et al. Hypothermiafor neuroprotection after cardiac arrest: systematic reviewand individual patient data meta-analysis. Crit Care Med2005;33:414—8.

4. Nolan JP, Deakin CD, Soar J, Bottiger BW, Smith G.European Resuscitation Council guidelines for resuscitation2005. Section 4. Adult advanced life support. Resuscitation2005;67(Suppl. 1):S39—86.

5. Sterz F, Safar P, Tisherman S, Radovsky A, et al. Mildhypothermic cardiopulmonary resuscitation improves out-come after prolonged cardiac arrest in dogs. Crit Care Med1991;19:379—89.

6. Markarian GZ, Lee JH, Stein DJ, Hong SC. Mild hypothermia:therapeutic window after experimental cerebral ischemia.Neurosurgery 1996;38:542—51.

7. Holzer M, Mullner M, Sterz, et al. Efficacy and safety ofendovascular cooling after cardiac arrest: cohort study andbayesian approach stroke 2006;37:1792—7.

8. Al-Senani FM, Graffagnino C, Grotta JC, et al. A prospective,multicenter pilot study to evaluate the feasibility and safetyof using the coolgard system and icy catheter following car-diac arrest. Resuscitation 2004;62:143—50.

9. Bernard S, Buist M, Monteiro O, Smith K. Induced hypother-mia using large volume, ice-cold intravenous fluid incomatose survivors of out-of-hospital cardiac arrest: a pre-liminary report. Resuscitation 2003;56:9—13.

0. Virkkunen I, Yli-Hankala A, Silfvast T. Induction of therapeu-tic hypothermia after cardiac arrest in prehospital patientsusing ice-cold Ringer’s solution: a pilot study. Resuscitation2004;62:299—302.

1. Kliegel A, Losert H, Sterz F, et al. Cold simple intravenousinfusions preceding special endovascular cooling for fasterinduction of mild hypothermia after cardiac arrest-a feasi-bility study. Resuscitation 2005;64:347—51.

2. Polderman K, Rijnsburger E, Peerdeman S, Girbes A. Induc-tion of hypothermia in patients with various types ofneurologic injury with use of large volumes of ice-cold intra-venous fluid. Crit Care Med 2005;33:2744—51.

3. Kim F, Olsufka M, Carlbom D, et al. Pilot study of rapidinfusion of 2 L of 4 ◦C normal saline for induction of mild

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hypothermia in hospitalized, comatose survivors of out-of-hospital cardiac arrest. Circulation 2005;112:715—9.

4. Jacobs I, Nadkarni V, The ILCOR Task Force on CardiacArrest and Cardiopulmonary Resuscitation Outcomes. Car-diac arrest and cardiopulmonary resuscitation outcome

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reports update and simplification of the Utstein templatesfor resuscitation registries. A statement for healthcare pro-fessionals from a task force of the International Liaison

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Committee on Resuscitation. Resuscitation 2004;63:233—49.5. de Latorre F, Nolan J, Robertson C, Chamberlain D, Baskett

P. European Resuscitation Council Guidelines 2000 for AdultAdvanced Life Support—–a statement from the Advanced LifeSupport Working Group 1 and approved by the Executive

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Committee of the European Resuscitation Council. Resusci-tation 2001;48:211—21.

6. Recommended guidelines for uniform reporting of data from

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out-of-hospital cardiac arrest: the ‘Utstein style’. Preparedby a Task Force of Representatives from the European Resus-citation Council, American Heart Association, Heart andStroke Foundation of Canada, Australian Resuscitation Coun-cil. Resuscitation 1991; 22:1—26.