Cardiac arrest is defined as a sudden and complete loss of cardiac function. Death is virtually inevitable unless basic life support is initiated promptly. Advanced life support should be commenced as soon as possible. The therapeutic strategies used for managing the arrest are based largely on the electrocardiogram tracing. Algorithms have been developed by the European Resuscitation Council, the American Heart Association, the Australian Resuscitation Council, the Heart and Stroke

Foundation of Canada, and the Resuscitation Council of Southern Africa (Am§r!c§n„,„H§a„rt.„,A§§.oc!ali.9D 1992; European R§§u§£iiatioD...,CoMn£il 199.2,). In 1997 the

International Liaison Committee on Resuscitation (ILCOR), composed of representatives from the above organizations, published Advisory Statements which included the Universal Advanced Life Support Algorithm shown in Fig 1 (!,ní!Ona!..L„iai.§OD..CO.mmiilt§§.On Resuscitation . . .1997).

Fig. 1 The Universal Advanced Life Support Algorithm for the management of cardiac arrest in adults: VF, ventricular fibrillation; VT, ventricular tachyarrhythmia; CPR, cardiopulmonary resuscitation. Note that each successive step is based on the assumption that the one before has been unsuccessful. (Reproduced with permission of the Advanced Life Support Working Group of the International Liaison Committee on Resuscitation.)

Cardiac arrest may be due to ventricular fibrillation, asystole, or electromechanical dissociation (pulseless electrical activity). Ventricular fibrillation

Ventricular fibrillation is the most common initial arrhythmia in cardiac arrest. It occasionally starts as pulseless ventricular tachycardia and then proceeds to ventricular fibrillation. Both rhythms can be treated identically. The most important therapeutic action for ventricular fibrillation is early defibrillation with d.c.

countershock (Fig 1). Survival after this rhythm decreases by 5 per cent per minute, even with basic life support. A precordial thump is still included in the algorithm as the first step in arrests witnessed by health-care professionals as it restores to sinus rhythm 40 per cent of patients with ventricular tachycardia and 2 per cent of patients in ventricular fibrillation. The risk of myocardial contusion and rib fracture is outweighed by the potential benefit of the rapid conversion of a pulseless arrhythmia to sinus rhythm. If the thump is unsuccessful, defibrillation should be performed immediately. One paddle should be applied below the outer half of the right clavicle, and the other just outside the position of the cardiac apex (ECG position lead V4-5). Good electrical contact must be assured by the use of electrode jelly pads and firm pressure. The energy sequence should be 200 J followed by 200 J and then 360 J. The first three shocks should be delivered within 30 to 45 s. A check of rhythm or pulse should be confirmed between each shock, but basic life support should be discontinued when automated external defibrillators are used between the first and third shock as this will only delay defibrillation. If there has been no success after the third shock, basic life support should be recommenced and, if not already done, the trachea should be intubated and intravenous access established. Basic life support should only be stopped for a maximum of 15 s to allow these procedures to be performed. Epinephrine (adrenaline) 1 mg is then given intravenously to increase the efficacy of basic life support and not as an adjuvant to defibrillation (Lindnerand K.o.s.t.e.L.19.92). A new set of countershocks at 360 J should follow as quickly as possible and should not be delayed if intubation or intravenous cannulation is difficult. Thereafter, the loop is repeated so that intravenous epinephrine 1 mg is given once every 3 min. After every three loops, other drugs may be appropriate. Sodium bicarbonate (50 ml of 8.4 per cent solution = 50 mmol) may be given if acidosis is suspected. It is better if acidosis is confirmed by arterial blood or central venous blood pH, bicarbonate, and base excess measurements. However, it must be remembered that intracellular acidosis bears little relationship to arterial or even mixed venous blood gas results. It is known that 8.4 per cent sodium bicarbonate is hyperosmolar and generates carbon dioxide that may give rise to a paradoxical intracellular acidosis as carbon dioxide can cross cell membranes very quickly. However, most clinicans will treat an arterial blood pH of less than 7.1 with 50 ml of 8.4 per cent sodium bicarbonate (note that if a mixed venous sample is taken, the pH will be approximately 0.3 units lower than that of the arterial sample).

The antiarrhythmic agents lidocaine (lignocaine), bretylium, and amiodarone may also be considered in this now desperate situation. Intravenous calcium, magnesium, and potassium may be of use in certain clinical situations when there is pre-existing or suspected electrolyte imbalance. Calcium has been implicated in ischemic tissue injury and should always be administered with caution. The number of loops used in the algorithm depends on clinical judgment; usually the resuscitation attempt should continue for 10 to 60 min and not be stopped while ventricular fibrillation exists. Persistent asystole is an indication that prospects of success are remote. Further resuscitation attempts should rarely last for more than 20 min unless hypothermia, near drowning, or drug intoxication are suspected of being associated with the arrest.

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