Basic life support (BLS) must commence immediately (Fig. 10-1):

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 4-5 cm) 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 rescue breathing (pocket mask is preferable to mouth-to-mouth respiration 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 performed as simultaneously as possible, defibrillation (150-200 J biphasic, or 360 J monophasic) takes highest priority (Fig. 10-2), followed by placement of IV access and intubation (if pt is less than fully conscious). One hundred percent O₂ should be administered by endotracheal tube or, if rapid intubation cannot be accomplished, by bag-valve-mask device. Once an advanced airway is placed, ventilate at rate of 1 breath every 6-8 s without interrupting chest compressions. Use quantitative capnography to confirm and monitor appropriate endotracheal tube placement.
6. Initial IV access should be through the antecubital vein, but if drug administration is ineffective, an intraosseous or 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 thought 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. 10-3.
8. Therapeutic hypothermia (cooling to 32-34°C [89.6-93.2°F] for 12-24 h) should be considered for unconscious survivors of cardiac arrest.