Defibrillation

DEFINITION

Defibrillation involves delivering a

high intensity electrical charge inorder

to depolarize the entire myocardium at

one time so that the fastest normal

pacemaker can regain control of the

pacing function of the heart.

INDICATION

•Ventricular fibrillation

•Asystole

DIFFERENCES BETWEEN MONOPHASIC AND BIPHASIC

SYSTEMS

•In monophasic systems, the current travels only in one direction -

from one paddle to the other.

•In biphasic systems, the current travels towards the positive

paddle and then reverse and go back; this occurs several times.

•Biphasic shocks deliver one cycle every 10 milliseconds.

•They are associated with fewer burns and less myocardial

damage.

•With monophasic shocks, the rate of first shock success in

cardiac arrests due to a shockable rhythm is only 60%, whereas

with biphasic shocks, this increases to 90%.

However, this efficacy of biphasic defibrillators over monophasic

defibrillators has not been consistently reported.

TYPES OF

DEFIBRILLATORS

Automated external defibrillators (AEDs):•These are useful, as their use does not require

special medical training.

•They are found in public places - e.g., offices,

airports, train stations, shopping centers.

•They analyze the heart rhythm and then charge

and deliver a shock if appropriate.

•However, they cannot be overridden manually

and can take 10-20 seconds to determine

arrhythmias.

Semi-automated AEDs:•These are similar to AEDs but can be overridden

and usually have an ECG display.

•They tend to be used by paramedics.

•They also have the ability to pace.

Standard defibrillators with monitor- may be

monophasic or biphasic.

Transvenous or implanted.

•An implantable cardioverter-defibrillator (ICD) is a device

combining a cardioverter and a defibrillator into one

implantable unit.

•It is thus a small battery-powered electrical impulse

generator that is implanted in patients who are at risk of

sudden cardiac death due to ventricular fibrillation and

ventricular tachycardia.

•The device is programmed to detect cardiac arrhythmia and

correct it by delivering a brief electrical impulse to the heart.

•In current variants, the ability to revert ventricular fibrillation

has been extended to include both atrial and ventricular

arrhythmias.

•There also exists the ability to perform biventricular pacing

in patients with congestive heart failure or bradycardia.

•The process of implantation of an ICD is similar to

implantation of a pacemaker.

PADDLES VERSUS ADHESIVE PATCHES

•Paddles were originally used but their use is being

superseded by adhesive patches.

•Adhesive patches are placed most commonly anterio-

apically - the anterior patch goes under the right clavicle

and the apical patch is placed at the apex.

•Adhesive electrodes are better, as they stick to the

chest wall, so there is no mess with gels.

•Paddles require at least 25 lbs of pressure, which is not

needed with adhesive electrodes.

•Adhesive electrodes also allow good ECG trace without

interference.

•They are also safer, as no operator required - although,

before discharging a shock, it is important to ensure

everyone is clear of the patient.

ENERGY LEVELS FOR DEFIBRILLATION

Monophasic - the cardiopulmonary resuscitation (CPR)

algorithm recommends single shocks started at and

repeated at 360 J.

Biphasic - the CPR algorithm recommends shocks

initially of 150-200 J and subsequent shocks of 150-360

J.

The Biphasic Trial in 2007 compared lower fixed (150,

150, 150 J) and gradually increasing energy (200, 300,

360 J) shocks for out-of-hospital cardiac arrests.

Escalating energy shocks were associated with more

frequent conversion and termination of VF as opposed

to low-level fixed shocks. This applied to patients who

remained in VF after the first shock.

PARTS OF DEFIBRILLATOR

•Machine

•Paddles- adult &pediatric

•ECG printout

•Alarm knobe for selecting energy

•Synchronizer

PROCEDURE

•It is an emergency procedure. The main principle is to

ACT QUICKLY. The steps of procedure involves

•Bring defibrillator to bedside

•Confirm diagnosis by palpating carotid pulse, or

analyzing the ECG

•Turn on the defibrillator

•Squeeze generous amount of jelly on to defibrillator

paddles, coat entire surface of the paddles with jelly by

rubbing paddles together, remove the excess jelly if it

spreads to the sides.

PROCEDURE

•Select the correct electrical charge on the defibrillator.

The average charge for an adult is 200 to 300 joules or

watt per second.

•Press the charge button to charge the capacitor. When

the intensity meter displays the required energy level. Place the paddles on the patient’s chest. Put one paddle

to the right of the sternum between the second and third

intercostal space and the other at the fifth intercostal

space on the left side of the chest near the apex of the

heart.•Make sure the paddles touch flat against the patient’s

body. If not it may cause burns in the patient

•Before delivering shock, tell everyone to stand clear off

the patient and his bed. If the patient is getting oxygen, it

should be turned off.

PROCEDURE

•Operator should not stand on wet floornor leaning

against the bed of the patient.

•Discharge the energy by pressing the discharge buttons

on the paddles simultaneously.

•Examine the ECG strip to see whether defibrillation has

altered arrhythmia and restored normal rhythm.

•Ask co-worker to start CPR. If desired rhythm not

restored, defibrillation is repeated with a higher energy

level.

•If the defibrillation is unnecessary, discharge the

machine by turning it off.Once the machine is

discharged, clean the paddles with soap and water,

making sure to remove all conductive jelly. Any jelly that

remains on the paddles will corrode the metal paddles.

CAUSES OF FAILURE OF DEFIBRILLATION

•Poor patient condition

Valvular diseases

Massive myocardial infarction

Cardiomegaly

Myocardial rupture and cardiac tamponade

Pulmonary embolism or infarction

Respiratory disease or trauma

•Prolonged cardiac arrest

•Inadequate cardio-respiratory resuscitative measures

Hypoxia in the patient

Acidosis

Alkalosis

Electrolyte imbalance

•Drug toxicity

•Inadequate sympathetic tone

•Inadequate electrical current delivered to the heart

Defective equipment

Poor paddle position

Excessive conductive jelly between paddles

Barrel shaped chest of the victim

•Inexperienced operator

COMPLICATIONS

•Damage to myocardium due to repeated

high energy electrical shocks

•Chest burns due to repeated high-energy

discharges and poor contract between the

paddles and the skin

•Electrocution of the by-standers

•Formation of short circuits between

paddles due to excessive amount of

conduction jelly applied on the paddles. This

causes loss of electrical energy.

NURSING IMPLICATIONS

•As defibrillation is an emergency procedure, the

equipment should be ready at all times.

•It should be kept functioning all the time, and

should be checked before each shift.

•Each staff should be aware of its functioning

•The defibrillator should be tested daily for its

proper functioning. To test the defibrillator, follow

the steps as described below

•Set the defibrillator at 300 joules

•Depress the charge button on the defibrillator

until the display number matches the joules

setting

•Leave the paddles in their resting place on the

defibrillator and simultaneously press the

discharge buttons on both paddles

•When someone is getting ready for defibrillation,

the co-worker should begin with basic life

support.

•Patient should be continuously monitored after

defibrillation. He should never be left alone for the

first 24hr. vital signs are to be recorded very

frequently until they are stabilized. Oxygen should

be continuously given to the patient. Drugs

should be administered as ordered. Intake and

output chart to be maintained.

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