Physio Control LIFEPAK 20, Manual

Page: 177 / 227

Clinical Summaries
B-6 LIFEPAK 20e Defibrillator/Monitor Operating Instructions
Guidance for Selection of Shock Energy
Biphasic waveform technology is a standard in cardiac defibrillators. The study summarized here
1
provides the best information available on which to base energy selections for cardioversion with this
waveform.
For cardioversion of atrial fibrillation , the results of this study provide specific guidance for
three possible strategies in selection of shock energy levels.
• To optimize for more rapid cardioversion and fewer shocks, select the same biphasic energy
levels used previously with monophasic defibrillators (e.g., use 200 J biphasic instead of 200 J
monophasic). This can be expected to increase the success rate yet decrease the peak
current of the first and subsequent shocks.
• To maintain shock efficacy equivalent to that previously observed with monophasic shocks,
select a biphasic energy level of about one-third the energy previously used for monophasic
shocks (e.g., use 100 J biphasic instead of 300 J monophasic).
• To optimize for low initial and cumulative energy using a step-up protocol, select 70 J for the
first shock and use small increases in energy if further shocks are needed.
Each of these strategies should provide effective cardioversion therapy while substantially
reducing the amount of peak current to which the heart is exposed.
For cardioversion of atrial arrhythmias other than atrial fibrillation , the data available to
guide the selection of energy settings is very limited. It is likely that biphasic doses below 50 J will
provide high success rates when treating atrial flutter and paroxysmal supraventricular
tachycardia. However, until more clinical data becomes available, it may be advisable to use the
same energy settings for biphasic shocks as are customarily used for monophasic shocks.
Arrhythmias may persist for a variety of reasons unrelated to the type of waveform used for
cardioversion. In persistent cases, clinicians continue to have the option to either increase shock
intensity or switch to an alternate electrode placement.
1
Koster R, Dorian P., et al. A randomized trial comparing monophasic and biphasic waveform shocks for external
cardioversion of atrial fibrillation. American Heart Journal , 2004;147(5):K1-K7.