Introduction

Over 85% of sudden cardiac death patients are in Ventricular Fibrillation(VF) when they collapse.

The ability to reverse ventricular fibrillation fades from 80% to 0% rapidly. From the start of cardiac arrest the majority of patients will be asystolic within 14 minutes.

The provision of Basic Life Support (BLS) extends the period of VF. However, the only definitive way of reversing this rhythm and successfully resuscitating the patient is by immediate defibrillation.

When a crew of two attend, BLS must be commenced as the defibrillator is prepared, as some early evidence may be emerging that suggests that a minute's BLS prior to the first shock may improve outcome.

In the case of a single operator, once cardiac arrest has been diagnosed, the defibrillator should be attached to the patient, the rhythm assessed and shocks administered immediately, where required. BLS should be commenced in accordance with the appropriate resuscitation guideline.

Description

Defibrillation is the administration of a controlled electric shock. The defibrillator administers the shock through hand held, or hands free adhesive electrodes, which are placed on the chest wall, over the base and apex of the heart.

Uses

In cases of cardiac arrest, where patients are found to be in VF, pulseless Ventricular Tachycardia (VT) or in asystole where VF cannot be excluded, defibrillation must be performed immediately.

Method

Stepwise Automated External Defibrillation (AED):

• Confirm that the patient is not breathing and has no pulse.

• Expose the chest and ensure that it is as dry as possible.

• Follow usual safety procedures including removal of GTN patches and metal jewellery.

• Apply electrode pads to the chest, connecting the leads before application. One pad should be applied to the right of the sternum below the clavicle, the other over the cardiac apex.

• Switch on the defibrillator and ANALYSE RHYTHM.

• If shock is advised, the machine will automatically charge to 200 joules. Throughout the ANALYZE and CHARGING process warn the surrounding members of the public and one's colleague that you are about to shock the patient, and they MUST STAND CLEAR.

• Ensuring you and all others are clear – press shock button.

• Check pulse.

• If there is no pulse perform Basic Life Support for one minute as instructed by the voice prompts on the AED.

• After one minute you will again be prompted to 'stand clear' and analyse. If shock is advised, the machine will automatically charge to 360 joules. Warn the surrounding members of the public and one's colleague that you are about to shock the patient, and they MUST STAND CLEAR.

• Ensuring you and all others are clear – Press shock button.

• Continue to follow Resuscitation Guidelines, as required.

Complications

• Always ensure that the defibrillator batteries are fully charged.

• Always ensure that the pads are compatible with the defibrillator and are in date.

• An automatic or semi-automatic defibrillators, do not touch the patient during the ANALYSE phase, as this will give erroneous readings.

• REMEMBER on AEDs and semi-automatic defibrillators the analysis programme can be electronically corrupted by surrounding electro-magnetic and radio signals. (Do not use a cell phone or hand portable radio within two metres of the device).

• AEDs are not suitable for use on paediatric patients.

• BLS must always be initiated immediately using high flow O² therapy.

Additional Information

It is essential, at a cardiac arrest/ suspected cardiac arrest incident, to carry a defibrillator to the scene (see Equipment to Scene Guideline). The second crew member may simultaneously provide basic life support measures for airway and breathing control, whilst the first crew member concentrates on early defibrillation.