Cardiac Arrest

In adults, sudden cardiac arrest results primarily from cardiac disease (of all types, with more than 15% of sudden cardiac arrest attributable to acute coronary syndromes Overview of Acute Coronary Syndromes (ACS) Acute coronary syndromes result from acute obstruction of a coronary artery. Consequences depend on degree and location of obstruction and range from unstable angina to non–ST-segment elevation... read more , and a large majority associated with underlying cardiovascular disease). In a significant percentage of patients, sudden cardiac arrest is the first manifestation of heart disease. Other causes include circulatory shock due to noncardiac disorders (especially pulmonary embolism Pulmonary Embolism (PE) Pulmonary embolism (PE) is the occlusion of pulmonary arteries by thrombi that originate elsewhere, typically in the large veins of the legs or pelvis. Risk factors for pulmonary embolism are... read more , gastrointestinal hemorrhage Overview of Gastrointestinal Bleeding Gastrointestinal (GI) bleeding can originate anywhere from the mouth to the anus and can be overt or occult. The manifestations depend on the location and rate of bleeding. (See also Varices... read more , or trauma), ventilatory failure, and metabolic disturbance (including drug overdose).

In infants and children, cardiac causes of cardiac arrest are less common than in adults. The predominant cause of cardiac arrest in infants and children is respiratory failure due to various respiratory disorders (eg, airway obstruction, drowning Drowning Drowning is respiratory impairment resulting from submersion in a liquid medium. It can be nonfatal (previously called near drowning) or fatal. Drowning results in hypoxia, which can damage... read more , infection, sudden infant death syndrome [SIDS] Sudden Unexpected Infant Death (SUID) and Sudden Infant Death Syndrome (SIDS) Sudden unexpected infant death (SUID) is a term used to describe any unexpected and sudden death in a child less than 1 year of age, which often occurs during sleep or in the infant's sleep... read more , smoke inhalation Smoke Inhalation When smoke is inhaled, toxic products of combustion injure airway tissues and/or cause metabolic effects. Hot smoke usually burns only the pharynx because the incoming gas cools quickly. An... read more ). However, sudden cardiac arrest (the unexpected cessation of circulation without warning) in children and adolescents is most commonly due to arrhythmia Overview of Arrhythmias The normal heart beats in a regular, coordinated way because electrical impulses generated and spread by myocytes with unique electrical properties trigger a sequence of organized myocardial... read more resulting from a channelopathy Overview of Channelopathies Channelopathies are a group of genetic, autoimmune, or inflammatory conditions that alter cardiomyocyte ion channel function in a manner that predisposes to bradyarrhythmias or tachyarrhythmias... read more or underlying structural cardiac abnormality (1, 2, 3, 4 Etiology references Cardiac arrest is the cessation of cardiac mechanical activity resulting in the absence of circulating blood flow. Cardiac arrest stops blood from flowing to vital organs, depriving them of... read more ).

Cardiac arrest causes global ischemia with consequences at the cellular level that adversely affect organ function even after resuscitation and restoration of perfusion. The main consequences involve direct cellular damage and edema formation. Edema is particularly harmful in the brain, which has minimal room to expand, and often results in increased intracranial pressure and corresponding decreased cerebral perfusion postresuscitation. A significant proportion of successfully resuscitated patients have short-term or long-term cerebral dysfunction manifested by altered alertness (from mild confusion to coma), seizures, or both.

Decreased adenosine triphosphate (ATP) production leads to loss of membrane integrity with efflux of potassium and influx of sodium and calcium. Excess intracellular sodium is one of the initial causes of cellular edema. Excess calcium damages mitochondria (depressing ATP production), increases nitric oxide production (leading to formation of damaging free radicals), and, in certain circumstances, activates proteases that further damage cells.

Abnormal ion flux also results in depolarization of neurons, releasing neurotransmitters, some of which are damaging (eg, glutamate activates a specific calcium channel, worsening intracellular calcium overload).

Inflammatory mediators (eg, interleukin-1B, tumor necrosis factor-alpha) are elaborated; some of them may cause microvascular thrombosis and loss of vascular integrity with further edema formation. Some mediators trigger apoptosis, resulting in accelerated cell death.

In critically or terminally ill patients, cardiac arrest is often preceded by a period of clinical deterioration with rapid, shallow breathing, arterial hypotension, and a progressive decrease in mental alertness. In sudden cardiac arrest, collapse occurs without warning, occasionally accompanied by brief myoclonic jerks or other seizure-like activity.

Diagnosis of cardiac arrest is by clinical findings of apnea, pulselessness, and unconsciousness. Arterial pressure is not measurable. Pupils dilate and become unreactive to light after several minutes.

A cardiac monitor should be applied; it may indicate ventricular fibrillation Ventricular Fibrillation (VF) Ventricular fibrillation causes uncoordinated quivering of the ventricle with no useful contractions. It causes immediate syncope and death within minutes. Treatment is with cardiopulmonary... read more (VF), ventricular tachycardia Ventricular Tachycardia (VT) Ventricular tachycardia is ≥ 3 consecutive ventricular beats at a rate ≥ 120 beats/minute. Symptoms depend on duration and vary from none to palpitations to hemodynamic collapse and death. Diagnosis... read more (VT), or asystole. Sometimes a perfusing rhythm (eg, extreme bradycardia) is present; this rhythm may represent true pulseless electrical activity (previously termed electromechanical dissociation) or extreme hypotension with failure to detect a pulse.

The patient is evaluated for potentially treatable causes; a useful memory aid is "Hs and Ts":

In pediatric cardiac arrest, hypoglycemia is another potentially treatable cause.

Unfortunately, the cause of cardiac arrest often cannot be identified during cardiopulmonary resuscitation (CPR). Clinical examination, chest ultrasonography during CPR, and chest x-rays taken after return of spontaneous circulation following needle thoracostomy can detect pneumothorax, which suggests tension pneumothorax Diagnosis Tension pneumothorax is accumulation of air in the pleural space under pressure, compressing the lungs and decreasing venous return to the heart. (See also Overview of Thoracic Trauma.) Tension... read more as the cause of the arrest.

Cardiac ultrasonography can detect cardiac contractions and recognize cardiac tamponade Diagnosis Cardiac tamponade is accumulation of blood in the pericardial sac of sufficient volume and pressure to impair cardiac filling. Patients typically have hypotension, muffled heart tones, and distended... read more , extreme hypovolemia (empty heart), right ventricular overload suggesting pulmonary embolism Pulmonary Embolism (PE) Pulmonary embolism (PE) is the occlusion of pulmonary arteries by thrombi that originate elsewhere, typically in the large veins of the legs or pelvis. Risk factors for pulmonary embolism are... read more , and focal wall motion abnormalities suggesting myocardial infarction Acute Myocardial Infarction (MI) Acute myocardial infarction is myocardial necrosis resulting from acute obstruction of a coronary artery. Symptoms include chest discomfort with or without dyspnea, nausea, and/or diaphoresis... read more (MI). However, transthoracic cardiac ultrasonography should not be done if it requires significant interruption in CPR.

Rapid bedside blood tests can detect abnormal levels of potassium, helping to confirm suspicion that cardiac arrest was caused by an arrhythmia secondary to hyperkalemia.

History given by family or rescue personnel may suggest overdose.

Rapid intervention is essential.

(See also the 2020 American Heart Association [AHA] guidelines for CPR and emergency cardiovascular care and 2022 AHA Interim Guidance to Health Care Providers for Basic and Advanced Cardiac Life Support in Adults, Children, and Neonates With Suspected or Confirmed COVID-19.)

Cardiopulmonary resuscitation (CPR Cardiopulmonary Resuscitation (CPR) in Adults Cardiopulmonary resuscitation (CPR) is an organized, sequential response to cardiac arrest, including Recognition of absent breathing and circulation Basic life support with chest compressions... read more ) is an organized, sequential response to cardiac arrest; rapid initiation of uninterrupted chest compressions ("push hard and push fast") and early defibrillation of patients who are in VF or VT (more commonly adults) are the keys to success in achieving return of spontaneous circulation (ROSC). The 2020 AHA guidelines for treatment of cardiac arrest also advise rapid administration of a first dose of epinephrine for patients who have nonshockable rhythms.

In children, who most often have asphyxial causes of cardiac arrest, the presenting rhythm is typically a bradyarrhythmia followed by asystole. However, about 15 to 20% of children (particularly when cardiac arrest has not been preceded by respiratory symptoms) present with VT or VF and thus also require prompt defibrillation. The incidence of VF as the initial recorded rhythm increases in children > 12 years.

After immediate initiation of high-quality and uninterrupted chest compressions, defibrillation, and initial epinephrine, primary causes must be promptly treated. If no treatable conditions are present, treatment is determined by the cardiac rhythm. For patients in refractory ventricular fibrillation or pulseless ventricular tachycardia, defibrillation is done every 2 minutes and epinephrine is given every 3 to 5 minutes; amiodarone or lidocaine may also be given. For non-shockable rhythms, early administration of epinephrine has been associated with improved neurologically intact survival (1, 2 Treatment references Cardiac arrest is the cessation of cardiac mechanical activity resulting in the absence of circulating blood flow. Cardiac arrest stops blood from flowing to vital organs, depriving them of... read more ). IV fluid (eg, 1 L 0.9% saline, whole blood, or a combination for blood loss) should be given as needed to optimize volume status. If response to IV fluid is inadequate, clinicians may give one or more vasopressor drugs (eg, norepinephrine, epinephrine, dopamine, vasopressin). However, there is no definitive evidence that vasopressor administration during cardiac arrest improves return of spontaneous circulation or neurologically intact survival.

After return of pulses, postresuscitative care focuses on determination and treatment of cause, stabilization and prevention of rearrest, and optimization of neurologic outcome. In addition to treatment of cause, postresuscitative care may include methods to optimize oxygenation and ventilation and rapid coronary angiography in patients who have a ST-segment elevation (STEMI). The 2020 AHA guidelines suggest delayed coronary angiography should also be considered for patients without STEMI. Current recommendations are for targeted temperature management to therapeutic normothermia < 37.5° C, although AHA 2020 guidelines still recommend a lower temperature range. Research is ongoing to determine whether targeted temperature management with controlled hypothermia (32° C to 34° C) benefit select cardiac arrest survivors (3 Treatment references Cardiac arrest is the cessation of cardiac mechanical activity resulting in the absence of circulating blood flow. Cardiac arrest stops blood from flowing to vital organs, depriving them of... read more ).

Survival to hospital discharge, particularly neurologically intact survival, is a more meaningful outcome than simply return of spontaneous circulation.

Survival rates vary significantly; favorable factors include

While the American Heart Association 2020 Advanced Cardiac Life Support (ACLS) guidelines recommend cooling to a temperature range between 32° C and 36° C, more recent recommendations from the International Liaison Committee on Resuscitation Advanced Life Support (ALS) suggest actively preventing fever with a target temperature of ≤ 37.5° C rather than active cooling. It is still unclear whether certain groups of patients with cardiac arrest will have improved neurologically intact survival with targeted hypothermia management rather than with maintaining normothermia (1, 2, 3, 4, 5 Prognosis references Cardiac arrest is the cessation of cardiac mechanical activity resulting in the absence of circulating blood flow. Cardiac arrest stops blood from flowing to vital organs, depriving them of... read more ).

If many factors are favorable (eg, VF is witnessed in an intensive care unit or emergency department), 50% of adults with inpatient cardiac arrest may survive to hospital discharge. Overall, survival to hospital discharge in patients experiencing in-hospital arrest varies from 25 to 50%.

When factors are uniformly unfavorable (eg, patient in asystole after unwitnessed, out-of-hospital arrest), survival is unlikely. Overall, reported survival after out-of-hospital arrest is about 12%.

Only about 10% of all cardiac arrest survivors have good neurologic function, defined as minimal to moderate cerebral disability with ability to perform the majority of activities of daily living independently, at hospital discharge.

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