Adult Resuscitation

Background and Importance

Cardiopulmonary arrest is defined by the triad of unconsciousness, apnea, and pulselessness. It is estimated that more than 340,000 out-of-hospital cardiac arrests (OHCAs) occur annually in the United States, an estimated annual incidence of 140/100,000. Of these, approximately 180,000 are treated by emergency medical services (EMS). Most EMS-treated, OHCAs occur at home (70%) and are unwitnessed (50%). The proportion of EMS-treated cardiac arrest patients with an initial shockable rhythm of ventricular fibrillation (VF) or pulseless ventricular tachycardia (pVT) has declined over time to approximately 18%. Furthermore, the number of patients receiving bystander cardiopulmonary resuscitation (CPR) remains low, averaging 40%. Automated external defibrillators (AEDs) are applied prior to EMS arrival in a minority of cases.

Recent epidemiologic data from cardiac arrest registries indicate the survival rate to hospital discharge for EMS-treated, OHCA is about 10%. Comparatively, survival to hospital discharge following in-hospital cardiac arrest (IHCA) is about 26%. Of patients surviving to hospital discharge, independent of neurologic status on presentation, 79% have good neurologic function (cerebral performance category of 1 or 2). For comatose post-cardiac arrest patients who underwent hypothermic targeted temperature management (HTTM), the reported survival rate with good neurologic function has ranged from 20% to 50%. Regional and inter-institutional variability in survival exists after EMS-treated cardiac arrest. The entire system of care affects patient outcomes, and differences in outcomes across the country may reflect local practice variability and differences in delivery of the chain of survival.

Anatomy, Physiology, and Pathophysiology

Awareness of underlying causes of cardiac arrest helps direct therapy and diagnostic testing both during resuscitation and in the immediate post-cardiac arrest period ( Table 5.1 ).

Cardiac arrest with presenting rhythm of VF or pVT often has a primary cardiac origin. Coronary artery disease is a common pathologic condition found in patients who experience OHCA, and multiple observational studies have demonstrated disease rates comparable to those of patients undergoing clinically indicated coronary angiography. ^, Other primary cardiac etiologies of cardiac arrest include syndromes associated with sudden cardiac death due to ventricular dysrhythmias, including hypertrophic cardiomyopathy, Brugada syndrome, long QT syndrome, short QT syndrome, catecholaminergic polymorphic ventricular tachycardia, and arrhythmogenic right ventricular cardiomyopathy.

Cardiac arrest can result from non-cardiac origins, and common etiologies include circulatory causes, metabolic disturbances, and drug toxicities. Circulatory etiologies of cardiac arrest include tension pneumothorax, pericardial tamponade, pulmonary embolus, and hypovolemia/hemorrhage. These conditions must be recognized early to manage the underlying problem and maximize the chance of a successful resuscitation. The most common electrolyte disturbance leading to cardiac arrest is hyperkalemia, which results in progressive widening of the QRS complex that can deteriorate to pVT, VF, asystole, or pulseless electrical activity (PEA). Cardiac arrest from drug toxicity has specific characteristics, depending on the offending agent and presenting toxidrome. Specific therapy directed at drug toxicity (e.g., naloxone for opiate overdose) is essential, but may not be immediately effective depending on the agent involved. Prolonged resuscitation efforts that provide adequate perfusion may be needed (e.g., veno-arterial extracorporeal membrane oxygenation [VA-ECMO] for refractory cardiac arrest due to local anesthetic systemic toxicity).

Environmental etiologies including electrocution, hypothermia, and drowning can also result in cardiac arrest. Electrocution causes cardiac arrest through primary dysrhythmias or apnea. Alternating current in the range of 100 mA to 1 A (household and light industry) generally causes VF, whereas currents greater than 10 A (heavy industry or electrical transmission infrastructure) can cause ventricular asystole. Lightning produces a massive direct current electrocution that can result in asystole and prolonged apnea (see Chapter 130). Hypothermia-induced cardiac arrest can manifest with any electrocardiographic rhythm, and successful resuscitation depends on rapid rewarming, which often requires invasive measures (e.g., intravascular rewarming, peritoneal or thoracic lavage, or VA-ECMO; see Chapter 128). Once circulation is restored, patients should be warmed to a target of 32°C to 36°C (89.6° to 96.8°F) for 24 hours. Drowning is a form of asphyxia usually resulting in bradyasystolic arrest. Patients experiencing cardiac arrest secondary to hypothermia or drowning may benefit from prolonged resuscitation efforts.

Decision Making

Resuscitation

Management of cardiac arrest occurs in an orchestrated effort by a health care team led by a clinician who can monitor the efficacy and response to therapeutic interventions. Interventions should be performed rapidly and efficiently to maximize the chances of a good neurologic outcome. Restoration of adequate cardiac function is the defining factor of return of spontaneous circulation (ROSC), but restoration of good neurologic function is the defining metric of a successful resuscitation. The likelihood of achieving both of these goals decreases with every minute that the patient remains in cardiac arrest. Fig. 5.1 depicts an algorithm for the management of cardiac arrest.

The goal of CPR is to maintain vital organ perfusion until ROSC is achieved. The quality of CPR is perhaps the most underappreciated component of the resuscitation effort. Important quality performance measures include compression rate (100 to 120 compressions/min), compression depth (5 to 6 cm), chest compression fraction at least 80% (i.e., CPR performed 80 out of every 100 seconds of the pulseless interval), full chest recoil between compressions (no residual leaning between compressions), and ventilation rate (10 ventilations/min).

While chest compression–only CPR (hands-only-CPR) is recommended for lay-providers in the out-of-hospital setting, trained providers who are willing and able to provide ventilations should do so. A 30:2 compression-to-ventilation ratio is currently recommended for health care professionals in all adult resuscitation scenarios until an advanced airway has been established. While either bag-mask ventilation or an advanced airway strategy may be considered in any setting for adult cardiac arrest, the strategy employed should minimize CPR interruptions. If an advanced airway strategy is pursued, a supraglottic airway may be used and can be placed without interruptions to CPR. Endotracheal intubation may also be pursued in settings with high intubation success rates. Once an advanced airway is secured, CPR should be performed continuously, without pausing for ventilation, while providing one ventilation every 6 seconds (10 ventilations/min). Hyperventilation during CPR should be avoided, as it is associated with reduced cardiac output during CPR.