Shockable Rhythm Arm of The ALS Algorithm

Effective CPR and early defibrillation are the two proven interventions that increase survival to hospital discharge after cardiac arrest. Pulse checks (attempted palpation of carotid or femoral arteries) should be brief and only made in response to either:

• An organised rhythm detected on the monitor after 2 minutes of CPR
• The patient showing signs of life

The image illustrates the shockable rhythm arm of the ALS algorithm. Click on the image to enlarge.

Sequence of events

The sequence of events following identification of a shockable rhythm should be:

• The designated person selects the appropriate energy on the defibrillator (150-200 J biphasic for the first shock and 150-360 J biphasic for subsequent shocks) and presses the charge button
• While the defibrillator is charging, warn all rescuers other than the individual performing chest compressions to “stand clear” and remove any oxygen delivery device as appropriate
• Once the defibrillator is charged, tell the rescuer doing the chest compressions to “stand clear”; when clear give the shock

Pulse check

A pulse check is not recommended following shock delivery for the following reasons:

• It is rare for a pulse to be immediately palpable, even if a perfusing rhythm is restored
• Chest compressions will not induce VF
• Continuity of CPR is further lost

Use of a single recommended shock by well-trained teams should effectively allow near continuous CPR.

Learning bite

Pulse checks should be avoided unless an organised rhythm is detected on the monitor after 2 minutes of CPR, or the patient shows signs of life. Chest compressions should continue until the defibrillator is charged.

A range of defibrillation energy levels have been recommended by manufacturers and previous guidelines, ranging from 120-360 J. In the absence of any clear evidence for the optimal initial and subsequent energy levels, any energy level within this range is acceptable for the initial shock, followed by a fixed or escalating strategy up to maximum output of the defibrillator.[1]