CARDIOVASCULAR COLLAPSE AND SUDDEN DEATH.
Truc Phan, 5/9/2015
Unexpected cardiovascular collapse and death more often result from ventricular fibrillation in pts with acute or chronic atherosclerotic coronary artery disease. Other common etiologies are listed in Table 1. Arrhythmic causes maybe provoked by electrolyte disorders (primarily hypokalemia), hypoxemia, acidosis, or massive sympathetic discharge, as may occur in CNS injury. Immediate institution of cardiopulmonary resuscitation (CPR) followed by advance life support measures is mandatory. Ventricular fibrillation, or asystole, without institution of CPR with 4-6 min is usually fatal.
TABLE 1 CARDIAC ARREST AND SUDDEN CARDIAC DEATH Structural Associatons and Causes I. Coronary heart disease (Chronic, or acute coronary syndromes) II. Myocardial hypertrophy (e.g., hypetrophic cardiomyopathy) III. Dilated cardiomyopathy IV. Inflammatory (e.g, myocarditis) and infiltrative disorders V. Valvular heart diseases VI. Electrophysiologic abnormalities (e.g, Wolff-Parkinson-White syndrome) VII. Inherited disorder associated with electrophysiological abnormalities (e.g, congenital long QT syndromes, right ventricular dysplasia, Brugada syndrome, catecholaminergic polymorphic ventricular tachycardia) Functional Contributing Factors I. Transient ischemia II. Low cardiac output states (heart failure, shock) III. Systemic metabolic abnormalities A. Electrolyte inbalance (e.g, hypokalemia) B. Hypoxemia, acidosis IV. Neurologic disturbances (e.g, CNS injury) V. Toxic responses A. Proarrhythmic drug effects B. Cardiac toxins (e.g, cocaine, digitalis intoxication)
§ MANAGEMENT OF CARDIAC ARREST
Basic life support (BLS) must commence immediately (Fig. 11-1):
1. Phone emergency line (e.g., 911); retrieve automated external defibrillator (AED) if quickly available.
2. If respiratory stridor is present, assess for aspiration of a foreign body and perform Heimlich maneuver.
3. Perform chest compressions (depressing sternum 4-5cm) at rate of 100 per min without interruption. A second rescuer should attach and utilize AED if available.
4. If second trained rescuer available, tilt pt’s head backward, lift chin, and begin mouth-to-mouth respiration (pocket mask is preferable to prevent transmission of infection), while chest compressions continue. The lungs should be inflated twice in rapid succession for every 30 chest compressions. For untrained lay rescuers, chest compression only, without ventilation, is recommended until advanced life support capability arrives.
5. As soon as resuscitation equipment is available, begin advanced life support with continued chest compressions and ventilation. Although perfomed as simultaneously as possible, defibrillation ([IMG]file:///C:/Users/Admin/AppData/Local/Temp/msohtmlclip1/01/clip_image004.gif[/IMG]300J monophasic, or 120-150J biphasic) takes highest priority (Fig.11-2), followed by placement of IV access and intubation. 100% O2 should be administered by endotracheal tube or, if rapid intubation cannot be accomplished, by bag-valve-mask device; respirations should not be interrupted for more than 30s while attempting to inbate.
6. Initial IV access should be through the antecubital vein, but if drug administration is ineffective, a central line (internal jugular or subclavian) should be placed. IV NaHCO3 should be administered only if there is persistent severe acidosis (pH<7.15) despite adequate ventilation. Calcium is not routinely administered but should be given to pts with known hypocalcemia, those who have received toxic doses of calcium channel antagonists, or if acute hyperkalemia is though to be the triggering event for resistant ventricular fibrillation.
7. The approach to cardiovascular collapse caused by bradyarrhythmias, asystole, or pulseless electrical activity is shown in Fig. 11-3
8. Therapeutic hypothermia (cooling to 32-34oC for 12-24h) should be considered for unconscious survivors of cardiac arrest.
§ FOLLOW – UP
If cardiac arrest resulted from ventricular fibrillation in initial hours of MI, follow-up is standard post-MI carre. For other survivors of a ventricular fibrillation arrest, further assessment including evaluation of coronary anatomy, and left ventricular function, is typically recommended. In absence of a transient or reversible cause, palcement of an implantable cardioverter defibrillatior is usually indicated.