Chapter 29 Cardiac Arrest. © 2005 by Thomson Delmar Learning,a part of The Thomson Corporation. All Rights Reserved 2 Overview The History of Defibrillation

Chapter 29Cardiac Arrest

© 2005 by Thomson Delmar Learning,a part of The Thomson Corporation. All Rights Reserved

2

Overview

The History of Defibrillation Survival from Cardiac Arrest Automated External Defibrillator Heart’s Electrical Activity


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Overview

Dysrhythmia Assessment Management Postcall


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The History of Defibrillation

One of the most common causes of cardiac arrest is ventricular fibrillation (VF)

VF can only be treated by electrical countershock


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Defibrillator: machine used to deliver a shock Defibrillation: process of delivering shocks to

the heart


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Original ones were large and restricted exclusively to the operating room– Initially impractical for emergency use– Required patient’s chest to be opened and the

heart exposed


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Transition– 1956: Dr. Zoll created first external defibrillator

• External defibrillator remained in the hospital due to its large size

• EMS relied solely on CPR


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Transition– 1980: Dr. Eisenberg began a prehospital

defibrillation program• EMTs used one of the first AEDs in Seattle, Washington


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Survival from Cardiac Arrest

Reversal of cardiac arrest– Use of an AED is only one part of the formula for a

successful reversal of cardiac arrest

– Time is of the essence• Every minute of delay in calling EMS or getting a

defibrillator to the patient decreases the chance that the heart will respond to the shock

– Chain of survival


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Chain of survival– Early access– Early CPR– Early defibrillation– Early advanced cardiac life support


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If CPR is provided in less than 4 minutes and defibrillation is provided in less than 8 minutes, the patient has a 43% chance of survival


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For every minute that defibrillation is delayed to the patient, the chances of survival decrease by at least 10%

In the situation of cardiac arrest, every minute counts


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Early defibrillation saves lives.


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Components– Two large electrodes: pads placed

on patient’s chest– Cables (leads): connect patient to

the machine

Automated External Defibrillator


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Components – Battery source: generates electricity used to

perform the defibrillation– Internal computer: samples the heart’s electrical

rhythm through sensors in the electrodes


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Single largest advantage: does not require operator to learn the complex rules of electrocardiogram interpretation

Can interpret the rhythm and advise EMT to shock if appropriate



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AED equipment check – Case– Cables– Electrodes

• Should be sealed and not expired



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AED equipment check– Batteries

• Have backup batteries• Keep batteries recharged

– Supplies• 4 by 4 gauze or towel• Razor or bandage scissors

– Document



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Stop and Review

What is the definitive treatment for cardiac arrest due to VF?

What role does CPR have in the chain of survival?


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Cardiac Arrest

A common consequence of acute myocardial infarction (AMI) is cardiac arrest and death

Sudden cardiac death (SCD): the unexpected cessation of heartbeat within 2 hours of the onset of chest pain

More than 50% of SCD cases occur outside of the hospital


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Cardiac Arrest

Signs and symptoms– Chest pain– Cardiac symptoms– AMI can lead to

• Congestive heart failure• Cardiogenic shock• Sudden cardiac death


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Heart’s Electrical Activity

Every heartbeat has an electrical event that preceded the mechanical event

A normal electrical event within the heart is the propagation of electrical impulses from the SA node to the ventricles

ECG: graphical illustration of electrical activity from the heart as detected by an ECG machine


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An electrical impulse from the SA node travels to the AV node and the ventricle, causing the ventricle to contract and creating a pulse.


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Normal sinus rhythm– Complexes: grouped waves – Regularly repeating complexes are seen as a

rhythm on the ECG


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Normal sinus rhythm– SA node: natural source of a normal cardiac

complex– Normal sinus rhythm: electrical rhythm seen

when the heart’s electrical system functions properly


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Normal sinus rhythm.


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Escape pacemakers– SA node: the heart’s pacemaker – Automaticity: heart muscle’s ability to self-pace – Escape rhythm: resulting rhythm that may provide patient

with enough blood flow to stay alive until a physician inserts an artificial pacemaker


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Dysrhythmia

Any disruption of the normal sinus rhythm Heart muscle is irritable and fires chaotically


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Dysrhythmia

PVCs – Can disturb blood flow– Are felt as an irregular pulse– Can indicate ventricular irritability– Can progress to more potentially lethal

complications


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Dysrhythmia

Ventricular tachycardia (VT)– Ventricular rate of between 100 to 250 bpm– Does not allow enough time for blood to fill and

then empty – Results in little to no blood flow to the body


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Dysrhythmia

Ventricular tachycardia (VT)– Pulses are quickly lost; loss of

consciousness ensues– MUST DEFIBRILLATE!


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Ventricular Tachycardia

Watch this animation demonstrating ventricular tachycardia.


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Dysrhythmia

Ventricular fibrillation (VF)– Extensive area of damage from an AMI can

lead to VF– VF is a chaotic firing of multiple ventricular cells

that results in no organized rhythm – During VF, the heart simply quivers and does not

create any forward blood flow– MUST DEFIBRILLATE!


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Ventricular Fibrillation

Watch this animation demonstrating ventricular fibrillation.


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Dysrhythmia

Asystole– Arrhythmia with no electrical activity is left

• ECG will be flatline

• Defibrillation will have no practical value – Without a coordinated rhythmic contraction, blood

flow stops and pulses are lost– Without quick defibrillation, the myocardium will

suffer irreversible damage from lack of oxygen


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Asystole

Watch this animation demonstrating asystole.


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Dysrhythmia

Pulseless electrical activity (PEA)– Despite normal-looking electrical activity on an

ECG, a patient may still have cardiac compromise– Observe the patient, not the monitor


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Dysrhythmia

Pulseless electrical activity (PEA)– If no pulse, begin CPR despite ECG findings– PEA is not treated by defibrillation


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Assessment

Begin with scene size-up Initial assessment

– Cardiac arrest management focuses on ABCs and CPR


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Assessment

History– Try to gather a history

• It will be useful to both advanced providers and hospital personnel


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Assessment

Scene size-up– Always address scene safety – Fluids are a hazard to an EMT using an AED

• Can transmit electrical energy to EMT instead of to patient


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Assessment

Scene Size-up– Remove wet patient to a dry place

• Towel dry before defibrillating

– Never defibrillate a patient who is lying in a puddle of liquid


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Before using the AED, make sure the scene is safe.


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Assessment

General impression– Does dispatch information match what is

observed on-scene?– Get the global picture?– Is the telephone off the hook?– Open medication bottles?


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Assessment

Where is the patient? – In a chair?– Lying on the ground?– If no one witnessed the patient collapse,

consider spinal precautions


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Assessment

Initial assessment– Take spinal precautions if trauma suspected– Determine level of consciousness– Check ABCs


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Assessment

Initial Assessment– If patient is not breathing, give two breaths

and check pulse – If no pulse, prepare AED– If delay in getting AED prepared, start CPR


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Management

Attachment of AED– Attach electrodes to chest

• Attach electrode pads to the cables• Place one pad under the patient’s right clavicle and the

other on the patient’s lower left rib cage– Or place one on the anterior chest and one on the

posterior


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Management

Attachment of AED– Attach electrodes to chest

• Consult diagram on AED or on electrodes for placement• Cables are color coded

– White cable and pad go to right clavicle – Red cable and pad are attached to the lower left rib

cage


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There are two acceptable positions for the AED pads: A. anterior-anterior or B. anterior-posterior.


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Management

Preparation– Once AED has been attached, turn power on– Press Analyze

• If CPR is in progress, discontinue. • Usual command is “All clear!”• Motion from CPR can create motion artifact, causing AED

to mistakenly identify the ECG as VF


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Management

Preparation– If machine detects a shockable rhythm, it will

automatically charge– While machine charges, call “All clear!” again


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Management

Defibrillation– Shout: “I’m clear, you’re clear, we’re all clear!”– Press Shock button to defibrillate– Press Analyze again


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AED Used in the Field

Watch this video clip to see how an AED is used in the field.


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Management

Shocks– Shocks are delivered in sets of three repeated, or

stacked, shocks. – Goal: deliver three stacked shocks within 1 minute


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Management

Shocks– No need to check pulse between shocks– Check pulses at the beginning and the end of the

stacked shocks


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Management

Analysis– Once defibrillation sequence has ended, check

again for pulse and breathing – If none is present, resume CPR


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Special Situations

Artificial pacemakers– Don’t place pads over pacemaker– Move it slightly to the left and down several inches

toward the feet


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Special Situations

Automatic implantable defibrillator– Don’t place pads over the implantable defibrillator– Move it slightly to the left and down several inches

toward the feet


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Special Situations

Medication patches– Remove medication patches prior to defib

Hypothermia– Cold heart is resistant to attempts at defib– One set of stacked shocks only


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Special Situations

Pediatric considerations– Under 55 lb (25 kg) or 9 years old: defib with a

machine designed for pediatric use• Over 1 year old: Use adult AED if only machine at hand


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Cardiac Arrest

Transport– Transport quickly to closest appropriate hospital– Request ALS backup


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Cardiac Arrest

Postarrest care– Prepare to provide ventilations using a

bag-valve-mask– Adequate breathing: use high-flow

oxygen, non-rebreather mask– Unconscious but no trauma suspected:

consider placing in recovery position


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Cardiac Arrest

Ongoing assessment– Monitor patient closely during transport

in case of another arrest


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Cardiac Arrest

Field termination– Resuscitative efforts are not indicated in cases

where death is obviously irreversible– Consult local protocols for field termination

procedures– Offer support to the family and friends present– Show respect for the dead


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Postcall

Document thoroughly all actions or nonactions taken

Replenish supplies


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Postcall

Maintain competency in AED use– A semiannual refresher course in AED use is a

minimum expectation for many EMTs

Debriefing


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Stop and Review

What does the EMT need to do before pressing the Shock button on the AED?

What are two important safety considerations when shocking a patient?

Documents

Chapter 29 Cardiac Arrest. © 2005 by Thomson Delmar Learning,a part of The Thomson Corporation. All Rights Reserved 2 Overview The History of Defibrillation