Explanation of changes in strategy for management of VT/VF

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.

Defibrillator Energy

• 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.

Fine VF

• 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.