science behind the guidelines

Science Behind the Guidelines

John M. Field M.D. FAHA, FACC, FACEP Professor Medicine & Surgery

PSU College MedicinePenn State Heart and Vascular Institute

Senior Science Editor Emergency Cardiovascular Care Programs

AHA National Center, Dallas

ECC

The Importance of Early Defibrillation

…the perceived value of antiarrhythmics, vasopressors, advanced airway control and ventilation has declined markedly since 1992- the evidence is disappointingly weak that any of these interventions convey effective benefit to cardiac arrest patients.

CURRENTS AHA September, 2000

…the relative value of early defibrillation by reducing 1-2 minutes the interval between adult sudden cardiac arrest and a first defibrillatory shock does more to improve survival than the benefit from medications, airway interventions and newly designed defibrillation waveforms combined.

CURRENTS AHA September, 2000

The Importance of Early Defibrillation

Cobb, L. A. et al. JAMA 1999;281:1182-1188.

Survival Rates for Out-of-Hospital VF

1975 1977 1979 1981 1983 1985 1987 1989 1991 19993

40

35

30

25

20

15

10

5

0

First Response w

ith AED

%

100

75

50

0

AED

Stiell, I. G. et al. N Engl J Med 2004;351:647-656

Survival to Hospital Discharge

BLS

Variable Adjusted Odds Ration

Age < 75yrs

First Link- Early Access

Second Link- Bystander CPR

Third Link- Early Defib

Fourth Link- ACLS

1.6

4.4

3.4

3.7

1.1

1

Guidelines 2005

• Major changes

• Science Behind The Guidelines

• Major Challenges

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Guidelines 2005 SUMMARY• Major changes

• Science Behind The Guidelines

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Weighing the Evidence Grade of Evidence

Data from many large, randomized trials

Data from fewer, smaller randomized trials, careful

analyses of nonrandomized studies, observational

registries

Expert consensus

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Weighing the EvidenceData from clinical trials, significant Rx effects

Data from clinical trials, smaller Rx effects

Prospective non-randomized cohort studies

Historic or case controlled studies

Case series- no control group

Animal or model studies

Extrapolation

Common sense or common practice

ECC

LEVEL 1

LEVEL 8

Class of RecommendationsClass of Recommendations

Intervention is useful and effective

Evidence conflicts/opinions differ but leans towards efficacy

Evidence conflicts/opinions differ but leans against efficacy

Intervention is not useful/effective and may be harmful

II IIaIIa IIbIIb IIIIII

II IIaIIa IIbIIb IIIIIIClass of RecommendationsClass of Recommendations

Intervention is useful and effective

Evidence conflicts/opinions differ but leans towards efficacy

Evidence conflicts/opinions differ but leans against efficacy

Intervention is not useful/effective and may be harmful

No evidence of benefit-not harmful

II

ECC

Atropine (Asystole/PEA)

1mg IV Q 3-5 minutes (total dose-3mg)

No prospective studies support use

LOE – 3, 4, 5, 6

Class Recommendation- Indeterminate

ECCG

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• Emphasis effective chest compressions

• Ventilations delivered over one second

• Single compression-ventilation ratio

• Single shock followed by immediate CPR

Emphasis advanced airway

• Recommendation intraosseous access (IO)

Emphasis ET drug administration

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Major Recommendations

Key Emphasis

• Performance of High Quality CPR• Integration of CPR-BLS and

ACLSChest Compressions

• Early Defibrillation

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Effective chest compressions

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Major Recommendation

Coronary Perfusion Pressure (Ao diastolic - RA diastolic)Coronary Perfusion Pressure (Ao diastolic - RA diastolic)

CPR SYSTOLE(compression)

CPR DIASTOLE(relaxation)

Survival- Prolonged CPR Survival- Prolonged CPR

Berg RA et al: Circulation 2001;104:2465-70Berg RA et al: Circulation 2001;104:2465-70

00

55

1010

1515

2020

2525

3030

CP

P, m

m H

gC

PP

, mm

Hg

3535

24 hr Surv ROSC-EXP NO ROSC

Paradis

Compression Rate vs ROSC

20

40

60

80

100

QUARTILE

ROSCNRC

OM

PR

ES

SIO

N,

MIN

-1

Yu Circulation 2002;106:368Yu Circulation 2002;106:368

Push hard and push fastG

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ROSC Chest Compression RateIn-Hospital CPR

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100

95-140 87-94 72-87 40-72

NO ROSC

ROSC

Abella Circulation 2005:111

Rescue BreathsRescue BreathsWhat really happens-What really happens-

Ewy et al: Circulation 2005;111:2134-42Ewy et al: Circulation 2005;111:2134-42

12

16

00

1010

2020S

eco

nd

s fo

r 2

bre

ath

sS

eco

nd

s fo

r 2

bre

ath

s

14

Lay Med Std Medics

42% 58%

Lay persons: 2 rescue breaths interrupted CC for 16 secondsLay persons: 2 rescue breaths interrupted CC for 16 seconds

Actual CC/min=Actual CC/min=3939±11 Assar, 2000±11 Assar, 2000

16 secs

Myocardial Blood Flow and CPP Myocardial Blood Flow and CPP after 16 seconds of interrupting CPR after 16 seconds of interrupting CPR

5050

6060

7070

8080

9090

100100

1010

1212

1414

1616

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2020

2222

MB

F, m

l/100

g/m

inM

BF

, ml/1

00g

/min

CP

P, m

m H

gC

PP

, mm

Hg

Berg RA et al: Circulation 2001;104:2465-70Berg RA et al: Circulation 2001;104:2465-70 ICCM, WT, 10/04ICCM, WT, 10/04

P<0.001P<0.001 P<0.001P<0.001

15:215:2

15:215:2

ContinuousContinuous ContinuousContinuous

Probability - Successful Defibrillation Probability - Successful Defibrillation Interruption Chest CompressionInterruption Chest Compression

55101015152020252530303535404045455050

0 5 10 15 200 5 10 15 20Duration of hands-off, secondsDuration of hands-off, seconds

PPR

OS

CR

OS

C, %,

%

Eftestol T et al: Circulation 2002;105:2270-3Eftestol T et al: Circulation 2002;105:2270-3

n=156n=156

Intrathoracic PressureIntrathoracic PressureIncomplete Chest Recoil Incomplete Chest Recoil

0

5

10

15

20

25

100% 75% 100%

Coronary Perfusion Pressure

Mm

H

g

0

2

4

6

8

10

12

14

100% 75% 100%

Cerebral Perfusion Pressure

% Decompression

Yannopoulos Resuscitation 64:363

Incomplete Relaxation

Aufderheide Resuscitation 2005 64:353-62

0

10

20

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40

50

60

70

80

90

1 2 3 4 5 6 7

Compressions Linear (Compressions)

Com

pres

sion

s/

min

ute

Minute of Resuscitation

Ashton Resuscitation 2002

Rescuer Fatigue

30% - COULD NOT COMPLETE

1

Effective Chest Compressions

•Push hard and push fast

Limit Interruptions Allow full chest recoil Switch every 2 minutes

0

20

40

60

80

MIP CPP Surv

12

30

mmHg/min mmHg %

RATE/ min

Aufderheide TP Circulation 2004; 109:1960-5

Death by HyperventilationDeath by Hyperventilation

Deliver ventilations over one second

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Major Recommendations

Avoid Hyperventilation-Too fastToo much

Single Compression:Ventilation Ratio

Except- HCP 2 rescuer CPR for infants and children

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Major Recommendations

30:2