Defibrilllation

DEFIBRILLATION

D. SAI KUMAR

16.10.2014

Cardiac Arrest Algorithm

D – danger

R – response

S – shout

A

B

C

–

–

–

airway

breathing

circulation

D – defibrillation

DEFIBRILLATION

• Defibrillation is a process in which an

electronic device sends an electric shock

to the heart to stop an extremely rapid,

irregular heartbeat, and restore the normal

heart rhythm.

Importance of EarlyDefibrillation

• To giveactionscardiac

the victim the best chancemust occur within the firstarrest:

of survival, 3moments of a

1)

2)

3)

Activation of the emergency medical services

Provision of CPR

Operation of a defibrillator

AHA guidelines 2010.Section 6.Electrical therapies

Importance of EarlyDefibrillation

• Claude Beck (1894-1971) was a pioneer of heart surgery,. He also developed ways to revive heart attack victims, including the defibrillator and CPR

• In 1947, Beck successfully defibrillated his first patient, a 14-year-old boy whose heart went into fibrillation after an operation.

• The defibrillator used on this patient was made by James Rand, a friend of Beck. It had silver paddles (the size of large tablespoons) that were used in open-chest situations..

• Nine years later (1956) Paul Zoll used a more powerful unit to perform the first closed-chest defibrillation.

• In Belfast , ambulance-transported physicians first achieved pre-hospital defibrillation in 1966. Defibrillation by EMT’s (emergency medical technicians), without the presence of physicians, was first performed in Oregon , in 1969.

• The electrical shock, by depolarizing all excitable myocardium and possibly by prolonging refractoriness, interrupts reentrant circuits and establishes electrical homogeneity, which terminates reentry

• Produces electrical silence or ASYSTOLE

• This allows pacemaking cells in heart to recover

• Defibrillation is non synchronised delivery of energy during any phase of cardiac cycle

• Cardioversion is the delivery of energy synchronised with the large R waves of QRS complex

Automated ExternalDefibrillators

Manual Defibrillators

Automated Implanted CardioverterDefibrillator (AICD)

INDICATIONS

• As a rule, any tachycardia that produces hypotension, congestive heart failure, mental status changes, or angina and does not respond promptly to medical management should be terminated electrically.

• Very rapid ventricular rates in patients with atrial fibrillation and Wolff-Parkinson-White syndrome are often best treated by electrical cardioversion

ENERGY REQUIREMENTS

• Selection of appropriate current will reduce the need for multiple shocks and limit the myocardial damage per shock

• The energy set too low will leave the heart in ventricular fibrillation and a shock with the energy set too high may leave the heart in asystole or AV block

• The realtionship between bodysize and energy requirements for defibrillation has been under debate

• By the help of prospective out of hospital studies, the first shock energy for defibrillation was set at 200J in the mid 1980s

Defibrillation waveforms

• Two broad categories : monophasic and biphasic

• Biphasic waveforms deliver current that flows in positive direction for a specified duration then reverses and flows in a negative direction for the remaining milliseconds of the electrical discharge

• Biphasic waveforms are more superior than monophasic …. Still under investigation and debate

MONOPHASIC

* First-shock efficacy

360J54% - 63%*

360J77% - 91%*

BIPHASIC

Up to 85% *

* First-shock efficacy

120-200J150-200J86%—98%*

• Research has shown that repititive lower energy biphasic waveforms shocks (<200J) have equivalent or higher success for immediate termination of VF compared with monphasic waveform shocks that escalate the energy (200,300,400J) with successive shocks

Pads ,Paddles, and Positions

• Often neglected topic

• Should be placed in a position which maximises current flow through myocardium

• Even with proper placement of paddles only 4% to 25% of deliverd current actually passes through heart

• Recommended placement is termed either sternal- apex or anterior apex

• The sternal or anterior electrode is placed to the right of the upper part of the sternum below the clavicle

• The apex electrode is placed to the left of the nipple with the center of the electrode in the midaxillary line

• Alteranative method is to place one paddle anteriorly over the left apex and the other posteriorly behind the heart in left infrascapular location

• Avoid placement directly over any implanted pacemaker or defibrillator

Syncronised cardioversion

• Synchronisation prevents the unwanted induction of VF because it ensures that a shock hits during the absolute refractory period of the cardiac cycle

• Recommended in hemodynamically stable, widecomplex tachycardia requiring cardioversion, supraventricular tachycardia, atrial fibrillation and atrial flutter

Synchronised Cardioversion

•

•

Not effective in junctional tachycardiamultifocal atrial tachycardia

or

Problems with synchronization • Time delay

• Some times shock not delivered

IMPORTANT POINTS DURINGDEFIBRILLATION

Important Points DuringDefibrillation

•

•

•

•

Hairy chest

Wet chest

Breasts

PatchesWrenn, K. The hazards of defibrillation through nitroglycerin

patches. Ann Emerg Med 1990; 19(11): 1327-8

AICD / pacemaker•

Important Points DuringDefibrillation

Coupling agent•

– NO ARCING!!R. S. Hummel 3rd, J. P. Ornato, S. M. Weinberg and A. M. Clarke.Spark-generating properties of electrode gels used during defibrillation.A potential fire hazard. JAMA November 25, 1988; 260: 20

√

Defibrillator Burn

• Correct use of coupling agent or defibrillatorpads will prevent burns

Important Points DuringDefibrillation

• Paddle force

– 8kg in adult, 5kg in 1-8 year old using adult paddles

children when

• Paddle size– Minimum 150cm2, diameter 8-12cm

Important Points DuringDefibrillation

• Paddle position

1.

2.

3.

4.

Sternal - apical

Biaxillary

Right or left upper back – apical

Antero-posterior especially in atrialarrhythmias

4 positions are equally effective in shock• Allsuccess

Deakin CD, Sado DM, Petley GW, Clewlow F. Is the orientationof the apical defibrillation paddle of importance during manualexternal defibrillation? Resuscitation 2003;56:15—8

Important Points DuringDefibrillation

ALS Subcommittee 2010

Important Points DuringDefibrillation

• Fire

May be ignited by sparks from poorly applieddefibrillator paddles in the presence of anoxygen-enriched atmosphere

Miller, P. H. Potential fire hazard in defibrillation. JAMA 1972;221(2): 192. Early report of fire hazardduring defibrillation

Fires from Defibrillation during Oxygen Administration. Hazard. Health Devices Jul1994;23(7):307-8

Robertshaw, H. and G. McAnulty. Ambient oxygen concentrations during simulated cardiopulmonaryresuscitation. Anaesthesia

1998;53(7): 634-7

Theodorou et al. Fire Attributable to a Defibrillation Attempt in a Neonate. Pediatrics 2003;112:677-679

Important Points DuringDefibrillation

• One I clear, Two you clear, Threeclear

everybody

• Look back at monitor before shocking

• Paddles MUST be horizontal at all times!

How to defibrillate ?stop look go

1.

2.

3.

4.

5.

6.

7.

8.

9.

Attach electrodes to patient’s chest

Turn defibrillator on – select leads

Analyse the rhythm ?shockable

Apply coupling agent or

Select energy level

Apply paddles to chest

Charge the paddles

The “Clear” chant

Check monitor again

pads to patient’s chest

10.Discharge shock and return paddles to machine

If Flatline…

• Always double check that it IS a flatline

–

–

–

Check other leads

Check attachment of leads

Increase the size of rhythm to rule out fineventricular fibrillation

ALS Subcommittee 2010

What is wrong with this picture?

ALS Subcommittee 2010

References

1. American Heart Association CPR2010

Guidelines Nov

2. European Resuscitation Council Guidelines forResuscitation 2010

3. Braunwald’s textbook of cardiology 9th

edition