critical care medicine
Cardiopulmonary Resuscitation (CPR) in Adults
Defibrillation
The most common rhythm in witnessed adult cardiac arrest is Ventricular Fibrillation (VF) (VF); rapid conversion to a perfusing rhythm is essential. Pulseless Prompt defibrillation is the only intervention for cardiac arrest, other than high-quality CPR, that has been shown to improve survival; however, the success of defibrillation is time dependent, with about a 10% decline in success after each minute of VF (or pulseless VT). Automated external defibrillators (AEDs) allow minimally trained rescuers to treat VT or VF. Their use by first responders (police and fire services) and their prominent availability in public locations have increased the likelihood of resuscitation. Defibrillating paddles or pads are placed with one on the anterior right chest wall below the clavicle at the mid-clavicular line and the other over the left 5th or 6th intercostal space at the apex of the heart in the anterior-axillary line. Alternatively, the 2 pads may be placed with one pad over the anterior left hemithorax and the other pad on the posterior left hemithorax. Conventional defibrillator paddles are rarely present on modern defibrillators. When present, paddles are used with conducting paste; pads have conductive gel incorporated into them. One initial shock is advised as soon as a shockable rhythm is detected, after which chest compressions are immediately resumed. Energy level for biphasic defibrillators is between 150 and 200 joules (2 joules/kg in children) for the initial shock; monophasic defibrillators are set at 360 joules for the initial shock. Postshock rhythm is not checked until after 2 minutes of chest compressions. Subsequent shocks are delivered at the same or higher energy level (maximum 360 joules in adults, or 10 joules/kg in children). Patients remaining in VF or VT receive additional shocks every 2 minutes, along with continued chest compression and ventilation and optional Drugs for ACLS . 