2. Definition
™Defibrillator is a device that deliver a
therapeutic dose of electrical energy (electric
shock) to the affected heart (fibrillated heart or
other shockable rhythm) to force the heart to
produce more normal cardiac rhythm.
3. First demonstrated on dogs in 1899 by Jean-Louis Prévost & Frederic
Batelli, two physiologists from University of Geneva, Switzerland.
The first use on a human was in 1947 by Claude Beck,
professor of surgery at Case Western Reserve University.
Transthoracic defibrillation was first used in humans using
alternating current (AC)
Bernard Lown and his coworkers introduced direct current
(DC) defibrillators into clinical practice.
History
4. Defibrillator
Does not re-start the heart.
Stops all electrical activity.
If heart is still viable its natural pace maker will take over.
It is an emergency life saving procedure.
Probability decreases with time.
Mechanism
Current depolarizes the myocardium.
Induces asystole temporarily.
Allows SA node to take over coz it‟s the first to repolarize.
7. Loss of synchronization in heart is called as
fibrillation.
Types of fibrillation
Atrial fibrillation
Ventricular fibrillation
Defibrillator……
8. ™Defibrillation is the definitive treatment for the life threatening
cardiac arrhythmias ventricular fibrillation and pulseless
ventricular tachycardia
™
Ventricular fibrillation results from:
-Coronary occlusion
-Electrical shock
-Abnormalities of body chemistry
™
This irregular contraction of the muscle fibers causes non
effectively blood pumping and that results in a steep fall of cardiac
output.
Need for a Defibrillator
9. ™Ventricular fibrillation can be converted into a more efficient rhythm
by applying high energy shock to the heart.
™
This causes all muscle fibers to contract simultaneously, which may
then respond to normal physiological pacemaking pulses
Restoration of normal rhythm in fibrillating heart as achieved by direct current shock (arrow)
across the chest wall. The horizontal line after the shock shows that the cardiograph was blocked
or disconnected for its protection during the period of shock4
Ventricular fibrillation
10. This recommendation regarding CPR prior
to attempted defibrillation is supported by
2 clinical studies
JAMA. 2003;289:1389 –1395
JAMA. 1999;281:1182–1188
11. Applying a brief(.25 to 1 sec) burst of 60 HZ ac at an
intensity of around 6 A.
This application of an electrical shock to resynchronize
the heart is sometimes called counter shock.
If the patient does not respond, the burst is repeated
until defibrillation occurs. this method is known as ac
defibrillation.
AC DEFIBRILLATION
12. • It is cannot be successfully used to correct atrial
fibrillation.
• Successive attempts to correct ventricular fibrillation are
often required.
• Attempts to correct atrial fibrillation by this method often
result more serious ventricular fibrillation.
Disadvantage of using ac Defibrillator
13. In this method a capacitor is charged to a high dc voltage and
then rapidly discharged.
The amount of energy discharged by the capacitor may range
between 2 to 400joules with peak value of current 20A.
A corrective shock of 750-800 volts is applied within a tenth of a
second .
DC Defibrillation
15. • Energy storage capacitor is charged at relatively slow
rate from AC line.
• Energy stored in capacitor is then delivered at a
relatively rapid rate to chest of the patient.
• Simple arrangement involve the discharge of capacitor
energy through the patient’s own resistance.
PRINCIPLE OF DEFIBRILLATOR
16. Cont…..
The discharge resistance which the patient represents is
roughly a ohmic resistance of 50 – 100 ohms for a typical
electrode size of 80cm2.
The particular wave form is called “Lown” wave form.
The pulse width of this waveform is 10ms.
18. Manual external defibrillator
Electrodes placed directly around the heart area of chest.
Higher Voltage required than internal defibrillator.
Classified as -
Monophasic
Biphasic
19. Monophasic waveform Defibrillators
• Deliver current of one polarity.
• Current travels in one direction through the patients heart from one
paddle to another.
2 types :-
• The monophasic damped sinusoidal waveform (MDS) returns to
zero gradually
• Monophasic truncated exponential waveform (MTE) current is
abruptly returned to baseline (truncated) to zero current flow
21. Biphasic waveform Defibrillators
Current travels towards the +ve paddle & then reverses back.
Reversing of polarity, depolarizes all cells – called “burping”
response.
Classified into –
Biphasic truncated exponential waveform (BTE)
Rectilinear biphasic waveform (RLB)
RLB is better than BTE.
23. Advantages of Biphasic over Monophasic
Less power – Less trauma – Less battery.
Defibrillation more effective at low energy.
Fewer burns.
Less myocardial damage.
1st shock success rate in cardiac arrest due to shockable
rhythm –
Monophasic 60%
Biphasic increases to 90%
24. Manual internal defibrillator
Just like normal defilbrillator.
Electric charge is usually pumped in by internal
paddles in close or direct contact with the heart.
These devices are mainly used in operating theatres,
where the chest can be opened or being treated by a
surgeon
25. Semi-Automated External Defibrillator
Carries features of both full-manuated as well as
automated units of defibrillator.
Has an ECG display and manual override in it.
Generally used by paramedics and emergency medicine
technicians.
28. • AED is a portable type of external defibrillator that
automatically diagnoses the ventricular fibrillation in a patient.
• Automatic refers to the ability to autonomously analyze the patient's
condition.
• AED is provided with self-adhesive electrodes instead of hand held
paddles.
AUTOMATIC EXTERNAL
DEFIBRILLATOR
29. Automated external defibrillator (AED) cont…
Use does not require special medical training.
Found in public places – offices, airport, shopping mall.
The electrodes transmit information about the person's heart rhythm to a
controller in the AED.
The controller examines the electrical output from the heart and determine if
the patient is in a shockable rhythm or not and whether shock is needed.
The AED uses voice / visual prompts to tell user when to give the shock,
and the electrodes deliver it.
30. Paddle placement
4 Positions ----
Anterior-lateral > most convenient
Anterior-posterior
Anterior-left infrascapular
Anterior-right infrascapular
Anterior-lateral position ----
one – right of sternum below clavicle (2nd & 3rd ICS)
other – left 4th or 5th ICS mid axillary line
Reversing paddle markings “sternum & apex” does not affect defibrillation
Paddles placed along axis of heart.
AP- placement used in children with adult paddles.
31. Position of electrodes in pregnant patients :-
-One on right of sternum below the right clivcle
-Other left mid-axillary line avoiding breast
Paddle Size
- Adult – large paddles
10-13 cm diameter
- Pediatric – small paddles <1yr
Infant <10kgs – 4.5cm
Children >10kgs – 8cm
32. Steps of Defibrillation
Give 2min CPR before analysis.
Power on ADE
Attach electrode pad.
Check rhythm.
CLEAR.
Give shock(120-200J)
Resume CPR for 2mins before analysis cardiac rhythm again.
Consider giving – vasopressors / anti-arrhythmic‟s during subsequent
shock.
33. Defibrillation Success
Termination of VF into an organized rhythm or
asystole for atleast 5secs after shock.
Regardless of haemodynamic response
Start with –
150-200J Bisphasic truncated waveform
120J Rectilinear biphasic waveform
34. Monitoring
Monitor that patient stay in converted rhythm.
Keep patient well oxygenated.(SPO2 >98%)
Check serum K+ & Mg+ levels.
Maintain acid base balance.
Get 12 lead ECG after procedure.
Check for chest pain & access.
Get CPK & Troponin done.
Access patients skin.
35. Efficacy of Defibrillation
Trans – thoracic resistance is the major factor :
Which depends upon
Chest width & configuration
Ventilatory phase
Electrode skin interface
Electrode position
Electrode size
Force of electrode application
Energy level
Time between & no. of shocks
36. Factors to consider during defibrillation
1) Duration of VF
- the longer VF lasts, the harder it is to cure
- the quicker the batter
- shock early, shock often
- likelihood of resuscitation decrease by 7-10% with every
passing minute (Ann Emerg Med. 1993;22:1652–1658 )
37. 2) Myocardial environment / condition
Hypoxia, acidosis, hypothermia, electrolyte imbalance,
drug toxicity – impede conversion.
DO NOT DELAY SHOCK trying to correct these problems.
38. 3) Heart size / Body type
Pediatric requirement lower than adult
2J /kg initial shock
4J /kg repeat shock
Higher dose (upto 10J/kg)
Or adult maximum dose
Direct size / energy relationship in adults unknown
39. 4) Use largest size paddles
- completely contact chest without paddles touching each
other
- In pediatric minimum of 3cm distance between pads.
NOTE :-
- Small paddles : concentrate current, burn heart.
- Large paddles : reduces current density
40. 5) Previous counter shock
- repeated shocks lower resistance
- give one shock at a time & then continue CPR
- subesquent shock either equal or higher energy
6) Paddle size
( as discussed before)
41. 7) Paddle placement
- In pacemaker / ICD
atleast 12cm from generator
90 degree to AICD electrode
avoid placing pads directly over
no delay in defibrillation
- for other as described before…….
42. 8) Paddles – Skin interface
- only gel should be used (ECG gelly)
- cream, paste, saline pads etc.- not recommended
- gel decreases resistance to the flow of current
- never use alcohol
9) Paddle contact pressure
- firm pressure of 25 pounds
- in child <10kgs --- 3kg pressure
- in large children >10kgs --- 5kg pressure
- deflate lung, shortens the path of current
- do not lean on paddles : they slip
43. CARDIOVERSION
Cardioversion is the delivery of energy that is
synchronized to the large R waves or QRS complex.
It uses energy less than that used for defibrillation in
shockable SCA
Avoids delivering shock during repolarization period (T
wave on ECG)
44. Indications
- Atrial flutter
- Atrial fibrillation
- Re entry SVT
- Mono morphic VT
- Poly morphic VT
- Wide complex tachycardia of uncertain type
45. Contraindications
- Digitalis induced dysrythmias
- refractory to cardioversion
- may precipitate to more serious ventricular dysarythmias
- Junctional tachycardia or ectopics / multifocal atrial
tachycardia
- automatic foci not reverted by cardioversion
48. Elective Cardioversion
> Pre procedure conciderations
- History & physical examination (neurological)
- Concurrent illness
- Current medication including anticoagulation
- Fasting 6hrs
- Correct electrolyte imbalance
- Obtain 12 lead ECG
- Shaving at site if nessacery
- Digoxin to be withheld for 48hrs
- Continue other medications
- Transthoracic Echo or TEE
49. Cardioversion Anaesthetic Technique
Cardioversion is almost always performed under induction or sedation
(short-acting agent such as midazolam)
exceptions : if patient is hemodynamically unstable or if
cardiovascular collapse is imminent
- Amnesia / Sedation / GA – may be required
- Premedication – Midazolam 1 to 2 mg
- Pre oxygenation
- Airway maintained & supported
50. Cardioversion Anaesthetic Drugs
-- IV sedation – Propofol, Etomidate, Thiopentone,
Benzodiazepines
-- Etomidate
haemodynamically more stable
myoclonus 40%- interferes with ECG interpretation
-- Propofol
hypotension (boluses)
slow induction can attenuate this drop
51. Steps
- Check environment at procedure site
- Turn on defibrillator
- Anaesthetic technique as required
- Apply electrodes
- Press SYNC control
- Select applicationenergy level
- „3 clear‟ shout & look
- Deliver shock
52. Post Procedure Monitoring
- Record delivery energy & result
- Continuous ECG monitoring
- 12 lead ECG
- If successful response
check for peripheral pulses, BP, Airway patency & LOC
- Inspect skin under the padds
- If not successful, check & reassess
53. Complications of Cardioversion
- Systemic embolization
- Post shock cardiac arythmias
asystole
heart block
atrial / ventricular ectopics
ventricular tachyarrythmias
- Trasient ST & T wave changes
54. Cardioversion Defibrillation
Elective planned procedure Emergency life saving procedure
Synchronized shock Un-synchronized shock
Low energy shock High energy shock
There can be some delay No delay, immediate
Anti-coagulation needed No anti-coagulation needed
Less damage to myocardium More damage to myocardium
Used in most of the arrhythmias
except VT /VF
Used in VT / VF
