A Journal on Defibrillation strategies discussed in details

1. DEFIBRILLATION STRATEGIES
FOR REFRACTORY
VENTRICULAR FIBRILLATION
PRESENTER – DR JOYDEEP SARKAR
MODERATOR – DR INDRAJIT ABUJAM

5. Early Initiation of CPR
by Lay Rescuers
2020 (Updated): We recommend that
laypersons initiate CPR for presumed cardiac
arrest because the risk of harm to the patient is
low if the patient is not in cardiac arrest.
2010 (Old): The lay rescuer should not check
for a pulse and should assume that cardiac
arrest is present if an adult suddenly collapses
or an unresponsive victim is not breathing
normally. The healthcare provider should take
no more than 10 seconds to check for a pulse
and, if the rescuer does not definitely feel a
pulse within that time period, the rescuer should
start chest compressions.
Early
Administration of
Epinephrine
2020 (Unchanged/Reaffirmed):
With respect to timing, for cardiac
arrest with a nonshockable rhythm,
it is reasonable to administer
epinephrine as soon as feasible.
2020 (Unchanged/Reaffirmed):
With respect to timing, for cardiac
arrest with a shockable rhythm, it
may be reason- able to administer
epinephrine after initial defibrillation
attempts have failed.

6. Physiologic Monitoring of CPR
Quality
2020 (Updated): It may be reasonable
to use physiologic parameters such as
arterial blood pressure or ETCO2 when
feasible to monitor and optimize
2015 (Old): Although no clinical study
has examined whether titrating
resuscita- tive efforts to physiologic
parameters during CPR improves
outcome, it may be reasonable to use
physiologic parameters (quantitative
waveform cap- nography, arterial
relaxation diastolic pressure, arterial
pressure monitoring, and central venous
oxygen saturation)
Double Sequential
Defibrillation Not Supported
2020 (New): The usefulness of
double sequential defibrillation for
refractory shockable rhythm has not
been established.
Why: Double sequential
defibrillation
is the practice of applying near-
simultaneous shocks using 2
defibrillators. Although some case
reports have shown good
outcomes,
a 2020 ILCOR systematic review
found no evidence to support
double sequen- tial defibrillation and
recommended against its routine
use. Existing studies are subject to

8. BACKGROUND
• Despite advances in defibrillation technology, shock-refractory ventricular fibrillation remains
common during out-of-hospital cardiac arrest.
• Double sequential external defibrillation (DSED) AND
• Vector-change (VC) defibrillation
have been proposed as defibrillation strategies to improve outcomes in patients with
refractory ventricular fibrillation.

9. OHCA
• Out-of-hospital cardiac arrest (OHCA) is
defined as a cessation of cardiac
mechanical activity occurring outside of
the hospital setting, confirmed by
absence of signs of circulation
Reference NIH

10. REFRACTORY VENTRICULAR FIBRILLATION
• Defined as
• An initial presenting rhythm of ventricular
fibrillation or pulseless ventricular tachycardia
that was still present after three consecutive
rhythm analyses and standard defibrillations
separated by 2-minute intervals of
cardiopulmonary resuscitation (CPR).
Reference :NIH

11. STANDARD
DEFIBRILLATION
VS
VC DEFIBRILLATION
VS
DSED

12. METHODS
• Trial design
• Patient Recruitment and Randomization
• Trial protocol and Intervention
• Trial Outcomes
• Statistical Analysis

13. TRIAL DESIGN
• Three group Cluster Randomized Control Trial
• Crossover among 6 Canadian well trained paramedic services (around 4000 paramedics in
total)
• Place of Study - Ontario, Canada
• Duration of Study – March 2018 to May 2022

14. PATIENT RECRUITMENT
• Inclusion Criteria –
• All patients Aged > 18 years who had an OHCA and developed Refractory Ventricular Fibrillation of
presumed cardiac causes were eligible for the trial
• Exclusion Criteria –
• Patients with traumatic cardiac arrest
• Patients with DO NOT RESUSCITATE medical directives
• Patients with cardiac arrest due to drowning, hypothermia, hanging, or suspected drug overdose

15. RANDOMIZATION
• Randomization was performed at the level of paramedic service
• Random treatment sequences were computer generated by the coordinating center before
start of each trial
• Each cluster of paramedics crossed over every 6 months between 3 groups i.e. Standard
defibrillation, VC defibrillation and DSED at least once

16. TRIAL PROTOCOL AND INTERVENTION
• Standard protocol consistent with American Heart Association (AHA) guidelines for
treatment of VF
• Continuous Chest compressions were performed before application of defibrillator pads
• Each rhythm analysis was conducted at standard 2 minute intervals.
• VF was determined by manual defibrillator rhythm analysis performed by paramedics

17. CONTINUED…
• First 3 defibrillation attempts occurred with the defibrillation pads placed in ANTERO-
LATERAL position (Standard Defibrillation)
• Subsequent shocks were given one of the three types of defibrillation based on random
assignment for the cluster
• In this trial both intervention strategies (DSED and VC defibrillation) shared a common control
for comparison (Standard Defibrillation)

18. PRIMARY HYPOTHESIS
• Each of these strategies would be better than usual care at a P value of less than 0.05
• Baseline survival of 12% was assumed and hypothesized that survival to hospital discharge in
the DSED and VC groups would be a minimum of 9 percentage points higher than that in the
standard group

19. TRIAL OUTCOMES
• Primary Outcome-
• Survival to Hospital Discharge (30 day survival as a primary survival outcome after OHCA)
• Secondary Outcomes-
• Termination of Ventricular Fibrillation (absence of VF on subsequent rhythm analysis after
defibrillation and a 2 min interval of CPR)
• Return of Spontaneous Circulation (any change in rhythm to an organized rhythm with a
corresponding palpable pulse or BP documented by paramedics)
• A good neurologic outcome at hospital discharge (modified Rankin Scale Score of 2 or lower)

21. STATISTICAL ANALYSIS
28.7
12.4
4.9
30 day survival
1 to 3 shocks 4 to 10 shocks > 10 shocks
Estimation of 30 day survival
of Out of Hospital Cardiac
Arrest depending on the
number of shocks

22. CHARACTERISTICS OF THE PATIENTS

23. RESULTS

24. PRIMARY AND SECONDARY OUTCOMES

25. DISCUSSIONS
• Survival to hospital discharge was more common in the DSED group
• Termination of VF, ROSC, and a good neurologic outcome at hospital discharge more common
with DSED strategy
• The logistics of having a second defibrillator available may be a challenge
• Use of VC Defibrillation with single defibrillator may be an alternative therapeutic strategy

26. CONTINUED…
• Results suggest that although changing the vector of defibrillation (which changes
the distribution of voltage gradients during the shock) may have a role in terminating
ventricular fibrillation when previous standard defibrillation has been unsuccessful, it
is possible that increasing defibrillation energy with the use of DSED also plays a role.

27. LIMITATIONS
• The covid 19 pandemic caused substantial challenges in enrolling patients
• The trial did not achieve the planned sample size
• Stopped in the middle by Data and Safety monitoring board
• The treatment effect may have been overestimated, given the small number of events for the
primary outcome
• Trial protocol did not specify a fixed follow up time

28. LIMITATIONS CONTINUED….
• The length of hospital stay distributions in hospitals were not known
• Majority of patients were enrolled in the urban settings where a second set of defibrillator
was available
• General medication history, patient race, ethnicity, etc was not not known as study was
completed in prehospital environment
• Finally, trial was conducted with high degree of medical oversight and paramedic feedback,
which may noy be possible In all paramedic sevices