explanation of changes in strategy for management of VT/VF

Last reviewed 01/2018

explanation of Changes in strategy in management of VT/VF

Single shock vs three-shock strategy

In the 2005 guidelines a single shock was recommended as three-shock therapy would interrupt CPR and studies have shown significant survival benefits of single shock therapy.  However, all studies except one were before-after studies and all introduced multiple changes in the protocol, making it difficult to attribute a possible survival benefit to one of the changes.

Latest recommendations advises that if VF/VT occurs during cardiac catheterisation or in the early post-operative period following cardiac surgery (when chest compressions could disrupt vascular sutures), consider delivering up to three-stacked shocks before starting chest compressions. Although there are no data supporting a three-shock strategy in any of these circumstances, it is unlikely that chest compressions will improve the already very high chance of ROSC when defibrillation occurs immediately after onset of VF.

• initial biphasic shock should be at least 150 J
• initial monophasic shock should be 360 J (due to lower efficacy)
• for subsequent shocks both escalating and fixed strategies are recommended

Note: Although escalating shock energy resulted in reduction in the number of shocks to restore spontaneous circulation, rates of ROSC or survival to hospital discharge rates were unchanged.

• often difficult to distinguish from asystole
• often difficult to shock into perfusing rhythm
• better to continue good quality CPR may improve the amplitude and frequency of VF leading to more successful defibrillation.

Reference:

• (1) Resuscitation Council (UK). Resuscitation Guidelines 2010.