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Cardiac Arrest


Shira A. Schlesinger

, MD, MPH, Harbor-UCLA Medical Center

Last review/revision Sep 2021 | Modified Sep 2022
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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 oxygen, and, if left untreated, results in death. Sudden cardiac arrest is the unexpected cessation of circulation within a short period of symptom onset (often without warning). Sudden cardiac arrest occurs outside the hospital in more than 350,000 people/year in the US, including an estimated 5000 infants and children, with a 90% mortality rate.

(See also the American Heart Association [AHA] 2020 update of heart disease and stroke statistics for out-of-hospital and in-hospital cardiac arrest.)


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 Overview of Arrhythmias resulting from a channelopathy or underlying structural cardiac abnormality (1–3 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 ).

Etiology references


Cardiac arrest causes global ischemia with consequences at the cellular level that adversely affect organ function after resuscitation. 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 sodium causes 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.

Symptoms and Signs

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 a brief (< 5 seconds) seizure.


  • Clinical evaluation

  • Cardiac monitoring and electrocardiography (ECG)

  • Sometimes testing for cause (eg, echocardiography, chest imaging [x-ray, ultrasonography], electrolyte testing)

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.

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

Unfortunately, many causes are not identified during cardiopulmonary resuscitation (CPR). Clinical examination, chest ultrasonography during CPR, and chest x-ray 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 Diagnosis physiology, during 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, 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 Acute Myocardial Infarction (MI) (MI). Rapid bedside blood tests can detect abnormal levels of potassium. History given by family or rescue personnel may suggest overdose.


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

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.

Prognosis references


Rapid intervention is essential.

(See also the 2020 American Heart Association [AHA] guidelines for CPR and emergency cardiovascular care.)

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). Based on recent data, 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.

Primary causes must be promptly treated. If no treatable conditions are present but cardiac motion is detected or pulses are detected by Doppler, severe circulatory shock is identified, and IV fluid (eg, 1 L 0.9% saline, whole blood, or a combination for blood loss) is given. If response to IV fluid is inadequate, most clinicians give one or more vasopressor drugs (eg, norepinephrine, epinephrine, dopamine, vasopressin); however, there is no firm proof that ongoing vasopressor administration during cardiac arrest improves survival.

In addition to treatment of cause, postresuscitative care typically includes methods to optimize oxygen delivery, rapid coronary angiography in patients with suspected cardiac etiology, and targeted temperature management (32 to 36° C in adults) and therapeutic normothermia (36 to 37.5° C in children and infants–– 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 ).

Treatment references

More Information

The following is an English-language resource that may be useful. Please note that THE MANUAL is not responsible for the content of this resource.

  • American Heart Association 2020 Guidelines: These guidelines for cardiopulmonary resuscitation (CPR) and emergency cardiovascular care (ECC) are based on the most recent review of resuscitation science, protocols, and education.

Drugs Mentioned In This Article

Drug Name Select Trade
Adrenaclick, Adrenalin, Auvi-Q, Epifrin, EpiPen, Epipen Jr , Primatene Mist, SYMJEPI, Twinject
Pitressin, Vasostrict
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