PRINCIPLES OF CARDIOPULMONARY RESUSCITATION



Cardiopulmonary resuscitation consists of basic and advanced life support. Upon evaluating a patient with suspected cardiac arrest, one should first quickly establish that the patient is truly unresponsive and not breathing. If a pulse is not present, a precordial thump to the mid-sternum may be tried. Subsequently, the “ABC’s” of basic life support should be observed: Airway, Breathing, and Circulation. The mouth and phar­ynx should be examined to assure that no obstruc­tion is present. The tongue should be removed from the posterior pharynx by tilting the head backward and hyperextending the neck. This ma­neuver can sometimes cause resumption of spon­taneous respiration. If no breathing is noted, mouth-to-mouth or mouth-to-nose breathing should be initiated in four quick breaths. Time is often wasted trying to intubate a patient when ad­equate ventilation could be accomplished im­mediately via mouth or mask ventilation. One should check to see that the chest rises with each ventilation. If a carotid pulse is not present after the initial ventilations, external cardiac compres­sion over the lower half of the sternum (not over the xiphoid process) should be initiated. The ster­num should be depressed 3 to 5 cm, with the pa­tient lying on a hard surface. Compressions should be approximately 60 per minute, with a ratio of 5 compressions to 1 ventilation if two res­cuers are present. A single rescuer must give 15 chest compressions alternating with two venti­lations every 15 seconds.

Advanced life support should be initiated while basic life support continues. Defibrillation should be applied if indicated as soon as possible and is the single most definitive treatment available for most cardiac arrests. Oxygen should be admin­istered and an adequate intravenous access should be established. If circulation has not been restored quickly, sodium bicarbonate 1 mEq/kg IV is given to treat metabolic acidosis and is repeated after 10 minutes; further administration of sodium bicarbonate should be guided by blood gas and pH measurements once effective circulation is re­stored. Epinephrine (5 to 10 ml of a 1:10,000 so­lution administered via an intravenous, intracar­diac, or endotracheal route every 5 minutes as needed) is useful in treating asystole and also in aiding defibrillation of fine (low-amplitude) ven­tricular fibrillation. Atropine (boluses of 0.5 mg IV at 5-minute intervals to a total dose of approx­imately 2 to 4 mg) can be administered for pro­found bradycardia. Isoproterenol given as a con­stant infusion (2 to 20 |i,g/min) and titrated according to response may be used to treat brady-arrhythmias if atropine is ineffective. Emergency cardiac pacing may be attempted for bradyar-rhythmias if atropine and isoproterenol are un­successful.

Lidocaine, procainamide, or bretylium tosylate can be administered to help terminate ventricular tachyarrhythmias and prevent their recurrence. Intravenous furosemide and/or morphine may be used to relieve pulmonary edema. Calcium chlo­ride (2.5 to 5 ml of a 10 per cent solution repeated if necessary in 10 minutes) is given to increase myocardial contractility, especially if electrome­chanical dissociation is present. Calcium should be used with caution in a patient with known dig­italis excess. Calcium chloride will precipitate if given in the same intravenous line with sodium bicarbonate.

Electromechanical dissociation refers to the presence of cardiac electrical activity without ap­propriate mechanical activity. It may be caused by decreased filling of the heart (e.g., hypovole­mia, cardiac tamponade, pulmonary embolus) or severe myocardial pump depression that may re­spond to calcium. Emergency pericardiocentesis may be attempted if cardiac tamponade is sus­pected.

The widespread application of cardiopulmon­ary resuscitation via education of the public and extensive emergency care systems in many cities has increased both the number of cardiac arrest victims who reach the hospital and the number who survive to be discharged. Survival critically depends on the time from arrest to the initiation of resuscitation and is best if basic life support can be initiated within 3 to 4 minutes and more definitive therapy (i.e., defibrillation) shortly thereafter.