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CHAPTER
29
Cardiac Arrest
KEY TERMS
OBJ ECTIVES
all clear
artificial pacemaker
asystole
automated external
defibrillator (AED)
automatic implantable
cardioverter/defibrillator
(AICD)
automaticity
cardiac standstill
chain of survival
defibrillation
defibrillator
dysrhythmia
electrocardiogram (ECG)
escape rhythm
hypothermia
motion artifact
normal sinus rhythm (NSR)
premature ventricular
complex (PVC)
public access defibrillation
(PAD)
pulseless electrical activity
(PEA)
rhythm
ventricular fibrillation
ventricular tachycardia
Upon completion of this chapter, the reader should be able to:
1. Describe the assessment of the patient in cardiac arrest.
2. Describe the importance of early defibrillation.
3. Describe the importance of CPR to cardiac arrest survival.
4. List the indications for AED.
5. List the contraindications for AED.
6. Differentiate between a semiautomated and a fully automated
defibrillator.
7. Describe the fundamentals of AED operation.
8. Describe the safety considerations for AED use.
9. Describe the importance of advanced life support to patient
survival.
10. Discuss postresuscitative care of the arrested patient.
11. Discuss the function of the physician and AED use.
12. Discuss the importance of quality improvement for AED
programs.
OVERVIEW
One of the most challenging emergency medical services (EMS) calls
is for “man down, possible cardiac arrest.” Adrenaline surges through
the emergency medical technician’s (EMT’s) body, while preparing
for the mental and physical challenges of providing EMS in a life or
death situation.
In the not too distant past, a cardiac arrest was a death sentence.
The introduction of cardiopulmonary resuscitation, or CPR, in the late
1960s, improved survival somewhat. CPR, a combination of mouthto-mouth ventilation and chest compression, gave some hope to an
otherwise grim prognosis. Even with CPR, the changes of restoring a
heartbeat and ‘reversing’ a cardiac arrest were bleak.
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CPR in Progress
“Unit 24, man down, CPR in progress, Eagle Hills Office, Tower Lobby,
time out 16:45.” As he put the ambulance in gear and turned on the
lights and siren, Tony thought, “The timing couldn’t be worse, five
o’clock traffic is a mess and we are at least 15 minutes from the scene.”
As Tony passed by stopped cars on the road, he thought of the minutes
that were flying by for the patient.
As he pulled up to the curb in front of the tower building, Tony looked
in the window. Clearly CPR was in progress. One security officer was
using a pocket mask to ventilate while another was doing compressions.
Then he saw it—an AED was attached to the patient. “Maybe the patient
has a chance after all,” he thought. Tony quickly grabbed the quick
response kit and ran in the front door.
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What factors are working against this man’s survival?
What factors are working for this man’s survival?
Why is time important to this patient’s survival?
What can an EMT do to reverse the cardiac arrest?
Advances in medicine and new technology have made prehospital
cardiac arrest reversal more likely. EMTs, carrying special devices
called defibrillators, are able to provide definitive care to the cardiac
arrest victim. This chapter focuses on defibrillation, which is a procedure that can enable an EMT to save a life.
THE HISTORY OF DEFIBRILLATION
One of the most common causes of cardiac arrest is ventricular fibrillation, a chaotic, unorganized electrical malfunction of the heart that
results in no useful heartbeat. This chaotic electrical activity can be
stopped only by applying an electrical countershock. Once the ventricular fibrillation is halted, the heart can then begin normal organized beating.
During open chest surgery, surgeons have successfully been
“shocking” fibrillating hearts back to life for many years. The
machines that are used to deliver this shock are called defibrillators,
and the process of delivering a shock to the heart is called defibrillation. The difficulty was that early machines were large and were
restricted exclusively to the operating room. Furthermore, defibrillation required that the patient’s chest be opened and the heart exposed.
These facts made it impractical for emergency use.
In 1956, Dr. Zoll created the first external defibrillator. Although
somewhat cumbersome, it allowed defibrillation outside of the operating room. At about the same time, 1960, Dr. Kouwenhoven published a paper on closed chest compressions interposed with manual
ventilations, now known as CPR.
CPR quickly became popular among emergency services personnel,
but the defibrillator remained in the hospital. The advent of transistors
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and microprocessors brought with them the development of a smaller
defibrillator capable of being used in the prehospital environment.
In 1980, Dr. Eisenberg of Seattle, Washington, started a prehospital
defibrillation program using these new smaller defibrillators. His
hypothesis was that properly trained EMTs using defibrillators could
save many lives.
These EMTs used a defibrillator that could “read” the electrocardiogram (ECG), using a logic algorithm stored in a microprocessor, advise
the EMT to “shock,” or defibrillate the patient, then deliver the shock.
These were among the first automated external defibrillators (AEDs).
Chain of Survival
FIGURE 29-1 Early notification using
911, the first link in the chain of survival.
Using an AED on the patient in cardiac arrest is only part of the formula for a successful cardiac arrest reversal. Because ventricular fibrillation quickly degenerates from active, yet chaotic, electrical activity
to minimal electrical activity and then no activity at all, time is of the
essence when treating the cardiac arrest victim. Every minute of delay
calling EMS or getting a defibrillator to the patient decreases the
chance that the heart will respond to the shock.
The American Heart Association realized the importance of speed
and started to advance the concept of the chain of survival. Simply,
the chain of survival links all the elements of a cardiac arrest reversal
together. The chain of survival depicts the important steps that must
be taken to improve cardiac arrest survival.
Early Access
Quick notification of EMS is key to getting EMTs trained in the use of
an AED to the patient. Typically, EMS is accessed by calling 9-1-1.
Unfortunately, 911 service is still not universally available in the
United States.
One of the attractions of 911 is that it can provide the communications specialist the location of the call (Figure 29-1). Underlying this
ability to locate a call is the assumption that the call is being placed
from a stationary landline.
Although cellular telephones have made it easier for callers to
make calls from the scene of an incident, location identification has
been lost. Future cellular telephones will have this capacity.
FIGURE 29-2 Early CPR buys time for
the arrival of the AED.
Early CPR
CPR saves lives. There are some documented cases in which CPR alone
reversed a cardiac arrest, although CPR alone is often not sufficient.
Once EMS has been called, CPR helps preserve the brain until the EMT
and AED are at the patient’s side. Therefore, citizen CPR is still very
important to patient survival in a prehospital cardiac arrest (Figure 29-2).
Early Defibrillation
The definitive treatment for cardiac arrest due to ventricular fibrillation is defibrillation. The AED is an easy tool to use and allows rapid
application of defibrillation to the cardiac arrest victim. EMTs have
been targeted to learn AED use because they are the largest group of
prehospital care providers (Figure 29-3).
FIGURE 29-3
lives.
Early defibrillation saves
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Do not be surprised if an AED
has already been used before
EMS is on the scene. AEDs have
so improved in simplicity and
dependability that certain segments of the public are being
trained in the use of an AED.
Airlines now routinely train flight
attendants in the use of the AED.
Public access defibrillation (PAD), the availability of a
defibrillator to the lay public, is
rapidly becoming commonplace
in the shopping mall, on the factory floor, and in the business
office. CPR courses now routinely include AED training for
rescuers.
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Large public gatherings, such as
county fairs or sporting events,
are often scenes of cardiac
arrests. EMTs assigned to stand
by at these events should have
an AED readily available. The
AED left in the ambulance is of
no value to the patient who is in
the middle of the bleachers in
cardiac arrest.
Early Advanced Cardiac Life Support
Although an AED can reverse the fibrillation that led to the cardiac
arrest, it does not address the cause of the fibrillation, and recurrence
of the fibrillation is likely. Advanced life support (ALS) providers
trained in advanced cardiac life support (ACLS) have the skills and
knowledge to help protect the patient from further episodes of cardiac
arrest. These ALS providers can help to stabilize the patient before
and during transportation to the hospital.
Survival from Cardiac Arrest
Any chain is only as strong as its weakest link. If CPR is provided in
less than 4 minutes and defibrillation is provided in less than 8 minutes, the patient potentially has a 43% chance of survival. For every
minute that defibrillation is delayed to the victim of ventricular fibrillation, the chances of survival decrease by at least 10%. In the situation of cardiac arrest, every minute counts.
THE AUTOMATED EXTERNAL
DEFIBRILLATOR
The AED consists of two large electrodes (pads that are placed on
the patient’s chest) and cables (leads) that connect the patient to the
machine. A battery power source is also necessary to generate the
electricity that is used to perform the defibrillation. Figure 29-4 shows
the components of the AED.
The AED has an internal computer that samples the heart’s electrical rhythm through sensors in the electrodes. The computer measures
the waves in the heart’s electrical activity against a logic formula. If
the computer analysis indicates that the rhythm is ventricular fibrillation, or any other rhythm that will potentially respond to defibrillation (which will be discussed later in the chapter), then an audible or
visual warning advises the operator (EMT).
The single largest advantage of an AED is that it does not require
the EMT or operator to learn the complex rules of ECG interpretation.
The ECG is the record of the heart’s electrical activity. There are many
different patterns of electrical activity the heart can exhibit, each of
which requires a different management strategy. Some of these different patterns are discussed briefly later in this chapter, although the
EMT is not expected to interpret the rhythms after reading this chapter. Much more training is required to learn the technique of ECG
interpretation. The EMT can allow the AED to interpret the rhythm
and advise him to shock if appropriate.
Use of the AED
FIGURE 29-4 The automated external
defibrillator, or AED.
At the beginning of every shift, the EMT must ensure that the AED is
properly prepared for use. An overall inspection should be performed. The case should be intact. Cases may be broken when an
AED is accidentally dropped. A broken case is a potential electrical
hazard, and the AED should be taken out of service. Next, check the
Chapter 29 Cardiac Arrest
cables. Like the case, the cables should be intact. Frayed cables and
bare wires are dangerous and should be replaced. Finally, check the
electrodes. All electrodes should be sealed within a protective wrapper. Check the expiration date on the electrode package. Old electrodes become dried out and useless.
Batteries
The AED uses a battery for its power source. Batteries have a tendency to stop working when they are needed most. Every AED
should be equipped with a backup battery. The EMT should always
ensure that the primary battery and backup battery are adequately
charged.
Some types of batteries require regular recharging; others have a
charge that lasts for years without a need for a recharge (Figure 29-5).
The EMT should familiarize himself with the type of battery his
agency uses in its AED.
Supplies
In every routine equipment check, the EMT should ensure that the
proper accessory supplies are with the AED. Most AEDs used by
EMTs are equipped with a case that has several pockets used to hold
additional supplies that may be needed.
It is always advisable to have a spare set of electrode pads as well
as a spare battery on hand. Because an AED is used in life or death situations, it is important to have redundancy in critical supplies.
Families of patients have successfully sued EMS providers that
responded with an AED that had dead batteries.
The electrode pads must tightly adhere to the chest wall for optimal
delivery of the electrical energy. Moisture prevents proper adhesion.
A gauze 4-by-4 pad or a towel should be immediately available to
wipe down the chest before applying the electrodes.
Excessive chest hair can also interfere with adhesion of electrodes.
A pair of bandage scissors may be used to quickly shear hair. A razor
may also be used to shave hair from the chest for ideal electrode adhesion; however, it is often not necessary and may waste precious time.
A safety razor should, however, be available so that if it is necessary
to shave a portion of the patient’s chest, it can be done quickly.
After completing an AED equipment check, always document the
inspection and testing of the AED (Figure 29-6). Failure to document
an inspection leaves the EMT vulnerable should a lawsuit occur
owing to equipment failure. Be sure to report malfunctions and take
the faulty AED out of service until it can be serviced by a qualified
biomedical engineer.
CARDIAC ARREST
A common consequence of acute myocardial infarction (AMI) is cardiac arrest and clinical death. This event, defined as the unexpected
cessation of heartbeat within 2 hours of the onset of chest pain, is
called sudden cardiac death (SCD).
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EMTs who interact with ALS
providers frequently purchase
an AED that has an ECG display
screen and a paper ECG printout. These enable the ALS
provider to interpret the ECG.
Then the ALS providers can
override and manually operate
the AED. Usually a key or a
code is required to override the
AED control.
An EMT should not override
the AED. Without proper training,
the EMT may jeopardize the
patient’s life and risk his own ability to practice. For most EMTs,
the more commonly used AED
without a printout is satisfactory.
FIGURE 29-5 The rechargeable battery is the power source for the AED.
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Profuse sweating often occurs
during an AMI just before cardiac arrest. To improve electrode
adhesion, many EMTs will wipe
the chest down with a towel,
then spray the chest with an
antiperspirant. Be sure to use a
dry spray that says antiperspirant and not a deodorant.
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FIGURE 29-6 A precall AED checklist. (Reproduced with permission, © 2004, American Heart Association,
www.americanheart.org)
More than 50% of the cases of sudden cardiac death occur outside
of the hospital. Therefore, it is imperative for the EMT to understand
why cardiac arrest occurs and how to respond to it.
Signs and Symptoms
When a patient experiences chest pain or any of the other cardiacrelated symptoms described in Chapter 28, she may be experiencing
an AMI. Without prompt treatment, the AMI can lead to complications such as congestive heart failure (Chapter 27), cardiogenic shock
(Chapter 9), or SCD. Why does SCD occur? To understand the cause
of SCD, the EMT must first understand the heart’s normal electrical
activity.
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Normal Sinus Rhythm
To review, the heart is a pump. Pumps essentially have two interrelated components; an electrical system triggers the mechanical portion to do its job. The human heart is such a pump. It has an electrical
system that triggers the ventricles, the mechanical portion, to pump
blood.
The electrical impulse begins at the sinoatrial node (SA node), a group
of specialized cells located high in the right atrium. The impulse then
proceeds through the atria to the atrioventricular node (AV node),
another specialized group of cells that is situated between the atria
and the ventricles. From the AV node, the spark travels through a
defined bundle of muscle fibers, called the bundle of His. This bundle
of conductive fibers then splits into several branches known as bundle
branches. These bundle branches carry the electrical impulse to the
ventricular muscle. Within the ventricular muscle are additional specialized conductive fibers called Purkinje fibers, which will then stimulate the remainder of the ventricular muscle. For a review of these
structures, see Chapter 5.
As the electrical impulse is carried in this organized fashion
through the heart, the muscle is stimulated to contract in a coordinated fashion. Because the atria are stimulated by the electrical
impulse first, they will contract first, moving blood into the ventricles.
The ventricles will contract after they have been stimulated by the
electrical impulses received by the bundle branches and Purkinje
fibers. When the ventricles contract in an organized fashion, the effect
is for blood to be ejected out through the aorta. Figure 29-7 depicts the
path of the heart’s electrical stimulation.
Every heartbeat has an electrical event that precedes the mechanical
event. The normal electrical event within the heart is the propagation of
electrical impulses from the SA node to the ventricles as outlined. This
FIGURE 29-7 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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FIGURE 29-8
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Normally when a patient’s blood
pressure drops, for whatever
reason, the heart races to compensate for the loss. This reflexive tachycardia is a hallmark of
shock.
When an EMT determines
that the patient has a low blood
pressure, he naturally assumes
that the heart will be tachycardiac. This is not always the
case. If the electrical system of
the heart is damaged by an AMI,
then an escape pacemaker will
take over and the result will be a
bradycardiac escape rhythm.
When an EMT sees both
hypotension and bradycardia in
a medical patient, he should be
thinking about a possible AMI.
Normal sinus rhythm.
electrical activity from the heart can be detected by an electrocardiogram
(ECG) machine and graphically displayed on an oscilloscope or printed
on paper. This display is called an electrocardiogram.
An ECG normally displays a pattern of grouped waves, called complexes. These regularly repeating complexes are seen as a rhythm (a
regularly reccurring or repeating pattern) on the ECG. The natural
source of a normal cardiac complex is the SA node. Therefore, the
electrical rhythm that is seen when the heart’s electrical system is
functioning properly is called a normal sinus rhythm (NSR). An NSR
is the predominant natural rhythm of the heart.
Although it is not important for an EMT to be able to interpret an
ECG, the concept is helpful in understanding the physiology of cardiac arrest. Figure 29-8 shows an example of an NSR.
Escape Pacemakers
The normal source of a heartbeat is the SA node. The SA node is therefore referred to as the heart’s pacemaker because it establishes the rate
of stimulation and, therefore, contraction.
Heart muscle, or myocardium, has a unique ability to be its own
pacemaker. If for some reason the SA node or AV node fails to function properly, the ventricles have the ability to pace themselves,
although not as efficiently as the normal conduction system. This ability of the myocardium to self-pace is called automaticity.
The special ability of the myocardium to function independently is
valuable when the electrical system fails. The resulting rhythm, called
an escape rhythm, may provide the patient with enough blood flow to
stay alive until a physician can insert an artificial pacemaker (a manmade electronic device that will create an electrical impulse signaling
the heart to beat). An escape rhythm is slower and less efficient than an
NSR. Pacemakers are discussed later in the chapter.
Dysrhythmia
When the heart’s muscle is injured during an AMI, the muscle
becomes irritable, firing chaotically. This irritability can lead to
disruptions in the NSR. Any disruption of the NSR is called a
dysrhythmia.
Occasionally, a small group of irritated cells in the ventricles will
start to fire earlier than expected. This unnatural pacemaker creates a
premature ventricular complex (PVC) (Figure 29-9). A PVC inter-
Chapter 29 Cardiac Arrest
rupts the regular sinus rhythm and is therefore a dysrhythmia. PVCs
can disturb blood flow and are felt as an irregular pulse. PVCs can be
an indication of ventricular irritability.
If the signal from this small group of cells in the ventricles is fast
enough and strong enough, it can take over the heart’s own inherent
pacemaker. The ventricles often race at rates from 100 to 250 beats per
minute. The resulting ECG rhythm is called ventricular tachycardia.
Ventricular tachycardia creates a distinctive ECG, similar to a sine
wave pattern (Figure 29-10).
PVC
PVC
FIGURE 29-9
Unnatural pacemakers, created by an AMI, interrupt the NSR.
Infarct
FIGURE 29-10
Ventricular tachycardia robs the heart’s coronary arteries of life-giving blood.
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Chaotic ventricular
depolarization
FIGURE 29-11
Lethal ventricular fibrillation has no discernible rhythm.
Racing ventricles with a heart rate over 150 bpm do not have
enough time to fill with blood and then empty. The result is little or no
blood flow to the body, particularly to the coronary arteries. Pulses are
quickly lost, and the patient loses consciousness. If a normal heartbeat
does not resume quickly, the patient eventually dies. Defibrillation
can help to halt this rapid firing of irritable ventricular cells.
If the area of damage from an AMI is extensive, a large group of
cells in the ventricle becomes irritable. These irritable cells misfire and
can lead to sudden cardiac death. This process can be compared to a
nuclear explosion. A pound of uranium is dangerous and potentially
lethal. Several pounds of uranium are enough to create a spontaneous
nuclear reaction and even a nuclear explosion. Similarly, if enough
irritable ventricular myocardial cells fire prematurely, they can result
in ventricular fibrillation, a chaotic firing of multiple ventricular cells
resulting in no organized rhythm. During ventricular fibrillation, the
heart simply quivers and does not create any forward blood flow. The
ECG looks like a chaotic collection of waves that have no discernible
rhythm (Figure 29-11).
Without a coordinated rhythmic contraction, blood flow stops and
pulses are lost. The patient is in cardiac arrest. Without any blood
pressure, the coronary arteries are not filled and the heart muscle goes
without oxygen. Defibrillation can halt this chaotic firing of cells.
Eventually, the damage is so extensive, and the cells so damaged,
that all cardiac activity stops. The heart, in cardiac standstill, will lie
flaccid and unable to respond to any stimulus. The inert heart is in asystole. Because there is no electrical activity, it would not help to defibrillate the patient in asystole. CPR and rapid transport are indicated.
Asystole is a true arrhythmia (meaning “without rhythm”). Without
any electrical activity in the ventricles, the patient’s ECG will be flatline, or asystolic (Figure 29-12).
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Cardiac standstill
FIGURE 29-12
Doctors, nurses, paramedics, and
EMTs use the terms arrhythmia
and dysrhythmia interchangeably.
Although not strictly correct, it is
accepted practice.
Asystole, a true arrhythmia, occurs in cardiac standstill.
Pulseless Electrical Activity
There are certain conditions, such as severe blood loss, that will result
in no forward blood flow from the heart despite adequate electrical
activity. This is called pulseless electrical activity (PEA). It is important
for the EMT to realize that despite normal-appearing electrical activity
on an ECG, the patient may have cardiac compromise. The best bet is to
pay close attention to the patient and not to the monitor. If the patient
has no pulse, CPR should be begun, despite the ECG findings.
PEA is not treated with a shock, because there is nothing wrong
with the electrical activity. The proper course of action is CPR, 100%
oxygen, and rapid transport to the closest appropriate hospital where
the cause can be determined and treated.
Assessment
The assessment of the cardiac arrest victim is done similarly to the
assessment of any other unresponsive medical patient. Beginning
with a scene size-up, the EMT moves through the initial assessment
quickly, providing airway, breathing, and circulatory (ABC) support,
in that order. Because cardiac arrest requires significant work before
the completion of even the initial assessment, the EMT may never get
to a focused history and physical exam. It is, however, important that
the EMT gather any known history from the patient’s family while
care is being provided to the patient. Such historical information will
be useful to both advanced providers and hospital personnel.
Scene Size-Up
As discussed in Chapter 12, scene safety must always be addressed.
Fluids present a hazard to the EMT using an AED. Fluids can transmit
the electrical energy to the EMT instead of to the patient, resulting in
Safety Tip
Ventricular fibrillation is an interpretation of the ECG. For the
AED to make an accurate interpretation of the ECG, the AED
must be properly functioning.
Examples of problems include
failure to firmly connect the ECG
cables to the machine, dried
electrode gel on the pads (very
common), and cold skin.
Always check the patient
first. If the patient is awake, how
can she be in v-fib? Then check
the machine to see whether it is
functioning properly. Start at the
chest wall. Check the electrodes, then check the cable
connections, and finally check
the AED. The patient who is
awake does not have ventricular
fibrillation and should not be
shocked by an AED.
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injury to the EMT. Examples of fluids that can potentially transmit
electricity include snow, vomit, rain, urine, and pooled water. If the
patient is wet, she should be immediately moved to a dry place. Then
the patient should be toweled dry before proceeding. Never defibrillate a patient who is still lying in a puddle of liquid.
The patient’s body should also not be in contact with any metal
objects. Again, the metal can transmit the energy to the EMT instead
of to the patient. Examples of metal objects include sidewalk grates,
catwalks, and aluminum flooring. The patient should be moved
immediately, in an emergency carry, to a safe location before an AED
is used (Figure 29-13).
FIGURE 29-13 Before using the AED,
make sure the scene is safe.
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The AED should be a part of the
standard first-in gear for all medical calls. It is of no use in the
ambulance when it is needed
immediately on scene. The few
minutes lost retrieving the AED
from the ambulance might cost
the patient her life.
General Impression
The initial dispatch information may have been for a cardiac arrest.
CPR may already be in progress when the EMT arrives. In those cases,
the EMT enters the scene prepared.
In some cases, the dispatch information does not match the
patient’s situation. The call may have been received for a “person
passed out” or, commonly, for a “person seizing.” The EMT walks
into those calls unaware of the situation.
Stop and look around the scene first. Get the global picture. Tables
or lamps that are knocked over indicate a sudden collapse. If the telephone is off the hook, the patient may have been calling for help.
Medications, both over-the-counter and prescription, left out may
give a clue to the patient’s condition.
Gather a quick impression from the patient’s overall appearance.
Whether the patient is on the ground, sitting in a chair, or lying in a
bed, she will be unconscious if in cardiac arrest. Without blood circulating, the patient will be grossly cyanotic.
Try to obtain a chief complaint from any available family member
or bystanders. Ask whether anybody witnessed the patient’s collapse.
If the patient fell, ask whether the head struck anything on the way
down. If no one is available, or the answers are questionable, assume
spinal trauma.
Position the patient for further assessment. If the patient is unconscious, and CPR is likely to be needed, then the patient needs to be on
a firm surface. Move the patient out of the bed or chair and onto the
floor. If the room is small, such as a bathroom or a cramped bedroom,
consider quickly moving the patient to a larger room, such as the hallway or living room (Figure 29-14).
If the patient is unconscious, or is in cardiac arrest, the assistance of
ALS personnel is required. If ALS is available, then request assistance
to the scene right away.
Initial Assessment
FIGURE 29-14 Quickly move the
patient to a large enough area for CPR.
After completing the scene size-up, the EMT should immediately
determine the patient’s level of consciousness. If trauma is suspected,
an EMT should take manual stabilization of the head and spine first.
If the patient is unconscious and unresponsive to pain, the EMT
should immediately open the airway. After the airway has been
opened, the EMT should assess for the presence of breathing. If the
patient is not breathing, the EMT should deliver two rescue breaths
Chapter 29 Cardiac Arrest
using an appropriate ventilation device. After these breaths have been
given, the EMT should check for a carotid pulse, taking no more than
10 seconds for the pulse check.
If the patient is pulseless, the AED must be immediately prepared.
If sufficient personnel are available, or if there is a delay in getting the
AED to the patient’s side, CPR should be begun. Think of the assessment priorities as changing from ABC to ABCD: airway, breathing,
circulation, and defibrillation.
A detailed description of CPR can be reviewed in Appendix B.
Management
If an AED is immediately available, the EMT should quickly attach
the electrodes on the patient’s chest. First, attach the electrode pads to
the cables. Then place one pad under the patient’s right clavicle and
the other pad on the patient’s lower left rib cage. Alternatively, one
pad may be placed on the anterior chest and one on the posterior
chest as indicated in Figure 29-15.
A diagram for electrode pad placement is often found either on the
electrodes or on the AED. The cables are also color coded. The white
cable and pad are attached under the clavicle on the right. The red
cable and pad are attached to the lower left rib cage (see Figure 29-15).
Once the AED has been attached to the patient, the power should
be turned on. Usually the “power on” switch is prominently displayed. Every EMT should take a moment before the call to review the
operational features of the AED before using it.
Once the AED is operational, press the analyze button to activate
the AED. Often a voice prompt will advise the EMT or operator that
the AED is analyzing.
If CPR is in progress, the EMT or operator should instruct everyone
to stop. The usual command to the rest of the team is “all clear.” All
clear means that nothing, not even the bag-valve-mask, should touch
the patient. Motion from CPR can create motion artifact (a false ECG
reading created by vibration), causing the AED to mistakenly identify
the ECG as ventricular fibrillation (Figure 29-16).
FIGURE 29-15 There are two acceptable positions for the AED pads:
A. anterior-anterior or B. anterior-posterior.
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The definition of the term dead
weight is never clearer than
when an EMT has to move a
patient to the floor. If a backboard is available, consider sliding the seated patient onto the
backboard. Place the backboard
under the patient’s feet and then
slide the patient down the ramp.
Once the patient is on the backboard, move the backboard to
the floor. If the patient is in bed,
consider logrolling the patient
onto the backboard and then lifting the board onto the floor.
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A useful way to remember where
the colored electrodes are placed
is to say “white-right, red-ribs.”
The rhyme and letter coordination may make placement easier
to recall.
In some cases it may not be
practical or possible to place the
self-adhesive defibrillation pads
in the anterior-anterior position;
for example, if the person being
resuscitated has a very small
frame. The anterior-posterior
position is an acceptable alternative in those cases.
Similarly, it may be difficult to
place the apical pad or the defibrillator paddle in place on large
breasted patients. In those cases it
is acceptable to place the
left/apical self-adhesive defibrillation pad or paddle just lateral to the
breast or underneath the breast.
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Section 7 Emergency Medical Care
Safety Tip
Older defibrillators had manual
defibrillation paddles. These
paddles consisted of handles
and large metal electrodes. A
conductive medium, or defibrillation gel, had to be applied to the
paddles before use.
Paddles had many safety
issues. For one, the gel would
get all over the chest wall, and
sometimes all over the EMT.
The result was that the charge
was ineffective at best or could
shock the EMT.
It also took 20 pounds (8kg)
of pressure on the paddles to
get acceptable contact on the
chest wall. While applying this
pressure, many EMTs would slip
off the chest wall.
Newer
electrode
pads
permit hands-off defibrillation.
The distance of several feet
increases the margin of safety
for the EMT as well as improves
AED efficiency.
These newer self-adhesive
defibrillation pads are a safe and
often preferrable alternative to
standard defibrillation paddles
for the reasons stated earlier.
Street
Smart
There is little time during a cardiac arrest to stop and read the
electrode packaging for instructions. Many EMTs have learned
this simple mnemonic: Smoke
over Fire. The white cable,
smoke, is placed higher on the
body than the red cable, fire.
If the patient is already aboard the ambulance when she arrests,
and the ambulance is moving, instruct the driver to stop the vehicle.
Road vibrations can also create motion artifact that the AED could
misinterpret as ventricular fibrillation.
The AED may take a few seconds, after the analyze button has been
pressed, to determine whether the ECG is a shockable rhythm, a rhythm
that will respond to defibrillation. If a shockable rhythm is identified,
the AED will start to automatically charge. Most machines create an
audible warning or a verbal prompt or both. The audible warning
indicates that the AED is energizing. The verbal prompt typically
states “shock advised” or a similar statement.
While the AED is charging, call all clear again. Be sure that nothing
is touching the patient. The danger of an accidental shock, and the
safety of the team, cannot be overstressed. An EMT accidentally
shocked could potentially go into ventricular fibrillation, making a
bad situation worse by creating a second patient.
For the third and final time, the EMT or operator should call all
clear. Some EMTs use the mantra “I’m clear, you’re clear, we’re all
clear” while making a visual sweep of the patient before actually
defibrillating the patient.
Always perform a head-to-toe visual sweep with every defibrillation. Make a habit of looking at the patient’s nose, then looking at her
toes, and looking again at her nose, before pressing the button to activate the defibrillator. Defibrillation should never become so routine
that the EMT becomes complacent about safety.
Once all team members are physically clear of the patient, the EMT
or operator then presses the shock button. The shock button will
deliver the defibrillation from the AED to the patient.
The EMT or operator should immediately press the analyze button,
again stating all clear. The AED will analyze the ECG to see whether
the defibrillation was effective. If the shock was not effective, then the
process is repeated.
The goal of the EMT or operator is to deliver the shock in less than
one minute from arrival on-scene. It is not necessary to check for a
pulse between shocks.
Some EMTs may be taught to use a manual defibrillator. In
those cases, the first shock should be at maximum joules, usually
360 joules or the biphasic equivalent energy setting. Always follow the manufacturer ’s recommendations regarding the use of a
manual defibrillator.
Once the defibrillation sequence has ended, the EMT should
again check for pulse and breathing. If none is present, CPR should
be resumed. The AED can be used again after five cycles of CPR, or
approximately two minutes, to analyze the heart’s rhythm to see
whether a shockable rhythm is present. Remember that there are
several rhythms that will result in cardiac arrest yet are not
amenable to defibrillation; therefore, the machine will say “no
shock advised.” If the patient does not have a pulse, however, CPR
must be done and the patient should be transported quickly to the
closest appropriate hospital. Skill 29-1 describes the operation of
an AED.
Chapter 29 Cardiac Arrest
649
Defibrillation Energy
Original defibrillators delivered the electrical charge in what is called
a monophasic waveform; more specifically the monophasic truncated
exponential or MTE waveform.
Subsequent research and development created the more effective
biphasic waveforms. These energy waveforms require less energy to
effectively perform the same defibrillation, as does the monophasic
waveform.
Most newer models of defibrillators take advantage of this new
technology, using either the biphasic truncated exponential (BTE)
waveform at 150 joules to 200 joules or the rectilinear biphasic
waveform at 120 joules.
As most AED are self-calibrating and programmed to deliver the
optimal energy, the EMT does not have worry about which energy
setting to choose.
If the EMT is still using the older model monophasic defibrillator,
the program should be adjusted to deliver the maximum joules (usually 360) with each defibrillation.
The obvious problem in a cardiac arrest is that no blood flows from
the heart to the body. Although CPR provides some blood flow, CPR
cannot sustain the body for a long period. The best CPR provides only
about 30% of the normal cardiac output. The preferred option would
be to have the heart beat naturally.
If an electrical current is passed through the fibrillating heart muscle, the electrical current will stun, or shock, the heart. All uncoordinated contractions of the heart will immediately stop simultaneously.
Then natural sinus pacemakers can assume dominance over the heart
and an NSR can begin again.
For defibrillation to work, there must be some muscular activity in
the heart. Ventricular tachycardia and ventricular fibrillation are two
examples of shockable rhythms.
Asystole is an example of a nonshockable rhythm. Without any muscular activity, the heart will not respond to the defibrillation. In those
cases, CPR should be continued until ventricular fibrillation appears.
FIGURE 29-16 Motion, from road
vibrations or CPR, creates ECG motion
artifact.
Street
Smart
During an emotionally intense
event such as a cardiac arrest,
some new team members may
become so focused on what they
are doing that they mentally
block out extraneous noise,
including the command all clear.
Some EMTs or operators
will physically sweep above the
body with one hand, in a circular
motion. This action will break
another team member’s concentration and redirect his attention
to the EMT or operator. This
technique is very useful in noisy
environments as well.
Prolonged Down Time
In some cases the EMT may come across the patient with a prolonged
downtime, i.e. someone who has been in cardiac arrest for over four
to five minutes. In those cases it may be reasonable to start with a
round of CPR first; a round of CPR being five cycles of compressions
to ventilations at a ratio of 30:2.
Special Situations
There will be several situations that may require slight deviation from
the usual protocol in assessing and managing the patient in cardiac
arrest. The EMT should be familiar with these few situations.
Artificial Pacemakers
When the electrical system of the heart fails, causing bradycardia, a
cardiologist will place an artificial pacemaker into the patient. The
Safety Tip
If the patient is on the gurney, be
sure that no one’s foot is touching the metal undercarriage. It is
common for an EMT to rest his
feet on the lower bar of the gurney, out of sight of the EMT or
operator handling the AED.
Because the hard rubber wheels
of the gurney electrically isolate
the gurney, the EMT’s foot creates a new electrical pathway,
and the EMT will get shocked.
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Section 7 Emergency Medical Care
SKILL 29-1 Operation of an Automated
External Defibrillator
PURPOSE: To perform an external defibrillation,
嘼 Automated external
when indicated, on a patient in cardiac arrest.
defibrillator
嘼 Personal protective
STANDARD PRECAUTIONS:
clothing
1
The EMT must confirm that the patient is in cardiac arrest.
2
The EMT applies the electrode pads to the anterior chest wall, one to the apex of the heart at the
lower left rib cage and the other to the right sternal
border below the clavicle.
3
The EMT then turns the power on the AED while
calling “all clear.” The EMT must ensure that no one is
touching the patient.
(continues)
Chapter 29 Cardiac Arrest
651
SKILL 29-1 (continued)
4
The EMT then presses the analyze button and
presses the shock button, as advised. Again, the EMT
must ensure that no one is touching the patient.
5
After the shock has been performed, the EMT
must perform CPR for five duty cycles of ventilation
and compression (30:2). Then the EMT should check
for the presence or absence of a pulse. If the pulse is
absent, then another shock may be advised. If the
patient’s pulse returns, then the EMT checks for
breathing.
artificial pacemaker will create the impulse that signals the heart to
beat, ensuring a heart rate that will support a normal blood pressure.
An artificial pacemaker has a pulse generator and a set of wires that
lead to the heart. The pulse generator is usually placed in a pocket under
the skin, usually below the right clavicle, and the pocket is sewn shut.
The AED electrode pad is placed in about the same location as the
pacemaker. If a pacemaker is located under the skin, as indicated by a
bulge about the size of a silver dollar, then the AED pads should be
moved slightly to the left and down several inches toward the feet so
that the electrode is not over the pacemaker.
If the AED electrode is placed immediately over the pacemaker, the
AED may sense the pacer’s impulse, seen as a spike on the ECG, and
think the heart is beating regularly. Even more important, if the AED
functions correctly, detects the ventricular fibrillation, and a defibrillation is delivered, the pacer will absorb some of the defibrillation
energy and may not work properly afterward.
Automatic Implantable Cardioverter/Defibrillator
Using state-of-the-art microelectronics and more powerful microprocessors, physicians and biomedical engineers have created an
AED that can be placed within the body. The automatic implantable
cardioverter/defibrillator (AICD) is used for patients who are at risk
for developing recurrent ventricular tachycardia or fibrillation.
Often the patient’s family will tell the EMT that the patient has
an AICD. Many patients also carry an instruction card in their wallet or purse.
Similar to a pacemaker, the AICD has a generator/defibrillator and
a set of wires that leads to the heart. When the AICD senses an event,
Street
Smart
Many defibrillators use a technology called “biphasic defibrillation,” which allows use of a
lower overall energy setting
while still providing effective
energy to the heart muscle. The
EMT should be familiar with the
machine and technology used
by his agency.
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Section 7 Emergency Medical Care
Street
Smart
There have been several reported
cases of sparks produced by the
defibrillator leading to fire. In
those cases poorly attached selfadhesive defibrillator pads or
loose defibrillation paddles, along
with an oxygen enriched environment, lead to the fires. Care
should be taken to firmly apply
the defibrillator pads or paddles
and to remove oxygen sources
(i.e. oxygen masks or mask-bag
devices) from close proximity of
the patient during defibrillation.
such as ventricular fibrillation, it signals the defibrillator, which in
turn shocks the heart.
Because the AICD is internal and the wires are attached directly to
the heart, it takes very little energy to defibrillate the heart, 5–15
joules. The energy is so low, and the shock so small, that if the AICD
should function, or fire, while the EMT is doing CPR, he may feel a
mild tingling in the arms. This is not dangerous to the EMT yet can be
diminished by use of gloves, which act as an insulator.
The most common type of AICD looks very similar to an artificial pacemaker and is typically located in the same location under the right clavicle (Figure 29-17). When an AICD is detected, the AED electrode pads
should be moved slightly to the left of normal and several inches toward
the feet, in the same placement as used for a patient with a pacemaker.
Medication Patches
The use of transdermal patches has become increasingly popular. These
self-adhesive patches contain medication that is slowly absorbed through
the skin of the patient. Patches are an easy and convenient way of administering a medication that must have a steady level in the bloodstream.
Alternatively, the patient would have to take a pill several times a day.
Examples of transdermal patches include nitroglycerin patches,
used for cardiac patients; nicotine patches, used for cigarette cessation
programs; and hormone replacement patches, used in cancer prevention or treatment.
These transdermal patches often have an aluminum backing or the
drug’s paste medium is reactive to the defibrillation. Consequently,
when the patient is shocked, the patch either ignites, making a popping sound, or heats up, burning the patient.
Patches are generally worn on the upper chest, on the upper back,
or on the shoulders. Before operating the AED, the EMT must completely expose the patient’s chest wall and look for patches.
Gloves should always be worn when removing a patch. Lift the corner
of the patch by the tab and pull. The patch should come off easily. If medication is still visible on the patient’s skin, use a 4-by-4 pad and wipe it off.
Hypothermia
Hypothermia is a condition in which the body temperature drops
below 95°F (normal body temperature is 98.6°F). When the body temperature drops even further, to 90°F, the heart becomes quite irritable
and the patient is at risk for ventricular fibrillation.
Examples of patients who could suffer hypothermia include winter
hikers, persons immersed in cold water for a long time, and homeless
persons. Whenever a patient has been outdoors for a prolonged
period, consider the possibility of hypothermia.
The cold heart is resistant to attempts at defibrillation. Most medical
protocols and the American Heart Association’s Advanced Cardiac Life
Support (ACLS) course advocate delivering one shock only. If the heart
does not respond to these initial attempts, continue CPR and immediately transport the patient to the most appropriate emergency facility.
FIGURE 29-17 An automatic
implantable cardioverter/defibrillator is an
internal AED.
Transport
The patient in cardiac arrest, or having been reversed from cardiac
arrest, is a critically ill patient. Transport should be accomplished
Chapter 29 Cardiac Arrest
quickly, and the patient should be brought to the closest appropriate
hospital. Local protocols often govern the destination of particular
patients on the basis of hospital capability.
ALS should always be requested early in the resuscitation of a cardiac arrest victim. ALS providers can offer additional medications
and other procedures to the patient. If no ALS provider has arrived on
the scene by the time the patient is packaged and ready to go, an intercept should be attempted while en route to a hospital.
Postarrest Care
After the first shock, CPR should be resumed immediately. Pulse
checks, taking no longer than 10 seconds should proceed the next
shock. During a pulse check the EMT should perform a reverse CPR
check. Start by checking the carotid pulse. If a pulse is detected, then
the EMT should proceed to checking for breathing.
It is common that for several minutes after a successful defibrillation, and cardiac arrest reversal, the patient will need manual ventilation, using a bag-mask-device.
If the patient is breathing adequately, then place the patient on a
high-concentration oxygen mask and proceed to check the patient’s
level of consciousness.
If the patient remains unconscious and has no evidence of trauma,
turn the patient over onto her side in the recovery position. The recovery
position facilitates drainage of secretions from the mouth and decreases
the risk of aspiration. The electrodes should be left in place so that defibrillation may be quickly performed if cardiac arrest should recur.
Ongoing Assessment
During transport, the patient should be closely monitored. The ongoing assessment should involve continuous monitoring of the breathing and pulse. Recurrence of cardiac arrest is not uncommon. The
sooner it is discovered, the more likely the EMT will be successful in
reversing it again.
Should pulse and breathing be lost, the patient should again be
placed on her back; everyone should be clear of the patient; and the
AED should be allowed to analyze the rhythm.
Field Termination
There are some circumstances in which resuscitative efforts will not
be indicated. Circumstances in which death is obviously irreversible
are discussed in Chapter 3 and should be reviewed.
In some areas, ALS personnel may have a protocol to terminate
resuscitative efforts once they have become futile. Termination is
often done with direct contact with a physician.
Despite the death of the patient, it is important for the EMT to
offer support to the family or friends who are present. Family on
scene will need support when the decision is made that the patient
is dead.
After death has been declared, the EMT must remember to show
respect for the deceased. Speak to the family, calling the patient by his
or her common name. Use direct language, including the word dead.
Do not use terms such as “gone to a better place,” as these leave room
for misinterpretation.
653
Pediatric
Considerations
It is recommended that patients
who weigh less than 25 kilograms
(kg) or are under 9 years of age
be defibrillated with a machine
that is specifically designed for
use on children. Typically, a
smaller amount of electricity is
used and the machine might be
programmed to respond to electrical patterns more commonly
seen in pediatric patients.
While these pediatric-capable
defibrillators are intuitively preferred, recommendations based
upon the available literature conclude that an adult AED may be
used on children older than 1 year
of age if that is the only machine at
hand. Nonetheless, services that
respond to a large number of pediatric patients might consider maintaining an AED that is specifically
recommended for this age group.
The AED may be used on children, starting at age 1 to adult.
Pediatric defibrillation pads are preferred, but adult pads may be used
if those are all that are available.
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Section 7 Emergency Medical Care
Street
Smart
It is often useful to the family to
have one person on the crew
explain everything that is going
on with their loved one from the
very beginning of the resuscitation. It is not difficult for an EMT
to tell the family that their loved
one’s heart is not beating and
that she is not breathing, but
what they need to hear is that
you are trying to get the heart
restarted and are providing
breaths for the patient.
These explanations may
help the family come to terms
with the fact that everything is
being done, and may also help
them accept the death, if that is
the outcome.
This is not the time for morbid humor but a time for reverence.
Though humorous situations do sometimes occur at death, leave the
laughter until later.
Be prepared for the family’s reactions to death. Any reaction is possible, from denial to anger and rage to bargaining. These normal
behaviors represent either some way of fleeing the message or fighting the messenger. Do not take any behaviors personally.
Senior EMTs or clergy, or both, should be on hand, if possible, to
deal with grieving family members. Any death notification is a time
for high emotions and can lead to surprising reactions.
POSTCALL
After a cardiac arrest call, the EMT needs to document all actions accurately on the Patient Care Report (PCR). If CPR was not initiated, the
rationale for no CPR must be explained. If CPR and the AED were used,
then all care surrounding the event must be documented. A readout of
the AED’s memory or a copy of the tape should be attached to the PCR.
This documentation is generally reviewed by the quality improvement committee. A physician is often a part of this committee when
cardiac arrest calls are reviewed (Figure 29-18). The committee will
review the call for adherence to protocols as well as for comparison
with EMS standards. Nationally, EMS strives to have CPR begin
within 4 minutes, and defibrillation within 8 minutes.
All supplies used during cardiac arrest resuscitation should be
replenished immediately. Supplies typically used include defibrillation electrode pads (with cables) and the cassette tape or module. The
batteries should be rotated out of service, for recharging, and replaced
with fresh batteries. Use of a checklist can make this process easier.
Competency Assurance
FIGURE 29-18 Medical control will
want to review the Patient Care Report
whenever an AED is used by EMTs.
Many EMTs do not have an opportunity to use an AED regularly.
However, EMTs are expected to be proficient with the use of an AED
at all times. Therefore, it is important that EMTs practice AED use regularly. A semiannual refresher course in the use of an AED is a minimum expectation for many EMTs.
Physician oversight is a very important component to any defibrillation program. The involvement of a physician in the refresher
courses as well as call reviews can help improve the medical care
given by the EMT. Physicians are also involved in protocol development regarding the use of AEDs and resuscitation situations. The
EMT should be familiar with all relevant protocols in his area.
Debriefing
A cardiac arrest can be one of the most stressful calls to which an EMT
will respond. In some cases, the EMT may know the patient or the
patient’s family. This personal involvement creates some special stress for
the EMT.
Whenever a patient dies, an EMT will reflect on the care that was
given. Concerns about errors that may have been made and questions
Chapter 29 Cardiac Arrest
about personal competency surface. It is important that the EMT
explore these questions and resolve them.
A postcall debriefing may help the EMT work through the problems and, more important, improves performance for the next call.
CONCLUSION
The advent of AED technology has improved the chances of survival from prehospital cardiac arrest. An EMT, armed with an AED, can provide definitive
care in this critical situation. Combining assessment, AED, and CPR, the
EMT can contribute to the successful resuscitation of a victim of cardiac arrest.
T E ST YO U R K N O W L E D G E
1. List, in order, the steps of assessment for a patient in cardiac
arrest.
2. Why is early defibrillation important?
3. What are the indications for the AED?
4. Which ECG rhythms are “shockable” and which are
“nonshockable”?
5. What is the difference between a fully automatic and a
semiautomatic defibrillator?
6. List several safety considerations for the AED.
7. List several special conditions when the AED may have
limited use.
8. What is the importance of ALS to the care of the cardiac arrest
patient?
9. What is the function of the physician in AED practice?
10. What is a debriefing useful for?
I NTERN ET RESOU RCES
For additional resources on cardiac arrest and defibrillation, check out
these Web sites:
•
•
•
American Heart Association, http://www.americanheart.org
Heart Center Online, http://www.heartcenteronline.com
National Center for Early Defibrillation, http://www.earlydefib.org
F U RT H E R ST U DY
The critical moment. (1997). Journal of Emergency Medical Services,
22(1), supplement.
Newman, M. (1998). The chain of survival revisited. Journal of
Emergency Medical Services, 23(5), 46–52.
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