Defibrillating the patient

• Three shocks - give up to three shocks initially with energies of 200 J, 200 J, 360 J (or their biphasic equivalent). These shocks should be delivered one after the other without a delay. If all three shocks are necessary, try to give them in less than one minute.

• Between shocks - when more than one shock is required, the electrodes (AED) or paddles (manual defibrillator) should be left on the patient's chest while the defibrillator is recharging.

Be aware of the possibility of spurious asystole, a short delay after delivering a shock before the monitor recovers the display of the heart rhythm. Always reassess the rhythm just before delivering the shock (Bradbury et al. 2000). See also Chapter 9.

• Electrical and myocardial stunning - after defibrillation there is often a brief delay before the ECG settles and the rhythm can be interpreted. Successful defibrillation may be followed by a few seconds of asystole, referred to as electrical stunning (Resuscitation Council UK 2000b). Also, even if the rhythm is one that is normally compatible with a pulse, there may be a few seconds of impaired myocardial contractility. This is called myocardial stunning and results in a pulse that is weak and difficult to palpate. It is essential not to make a diagnosis of PEA or asystole too soon as defibrillation may have been successful. The algorithm indicates doing one minute of CPR before reassessing the rhythm and rechecking the pulse. It is important not to give any drugs during this minute. They could be harmful if a perfusing rhythm is present (AHA & ILCOR 2000).

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