What is the initial response to a cardiac arrest?
The initial response to a witnessed cardiac arrest is to confirm the diagnosis. Patients in arrest are unresponsive, apneic, and pulseless. Assistance should be called for immediately prior to any intervention. In the past, it was recommended to call for assistance after the initiation of cardiopulmonary resuscitation (CPR), but since 80–90% of patients with sudden cardiac arrest have ventricular fibrillation (VF), which is the most treatable dysrhythmia but which requires urgent defibrillation, the rescuer is advised to call first so that a defibrillator can be brought to the scene. The only exception is in the case of children less than 8 years of age, who usually arrest because of airway problems. In that case, an attempt at securing the airway should first be made.
Monitored patients should be treated according to the Advanced Cardiac Life Support (ACLS) protocol devised for their dysrhythmia. This includes basic life support (BLS), usually in the form of CPR, as well as adjunctive equipment for airway control, dysrhythmia detection and treatment, and post-resuscitation care. Unmonitored, unre-sponsive patients should have their airway assessed first followed by two breaths and a pulse check. In a witnessed cardiac arrest, a precordial thump may be indicated but CPR must be started immediately if the patient remains pulseless. As soon as possible, paddles or electrocardiogram (ECG) leads should be placed on the patient to determine the rhythm. If pulseless ventricular tachycardia (VT) or VF is the initial rhythm, the patient should receive up to three uniphasic countershocks of increasing power: 200 joules (J), 200-300 J, and 360 J, respectively. Biphasic equivalents are approximately half that of uniphasic doses. If VF or pulse-less VT is not the initial rhythm, or if the countershocks are unsuccessful, then chest compressions and ventilation should be continued and the patient treated accordingly (Figure 1.1).
The essential element in treating cardiac arrest is rapid identification and treatment. The goal of CPR is to provide oxygenated blood to the heart and brain until ACLS proce-dures are initiated. The best results (survival of approxi-mately 40%) are achieved in patients receiving CPR within 4 minutes and ACLS within 8 minutes of arrest, whereas survival is less than 6% when CPR and ACLS are started after 9 minutes.
The groups of patients most likely to be resuscitated include patients outside the hospital with witnessed arrests due to VF, hospitalized patients with VF secondary to ischemic heart disease, arrests not associated with coexisting life-threatening conditions, and patients who are hypother-mic or intoxicated. Patients with severe multisystem disease, metastatic cancer, or oliguria do not often survive CPR.