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.
Respiratory arrest Overview of Respiratory Arrest Respiratory arrest and cardiac arrest are distinct, but inevitably if untreated, one leads to the other. (See also Respiratory Failure, Dyspnea, and Hypoxia.) Interruption of pulmonary gas exchange... read more and cardiac arrest are distinct, but without treatment, one inevitably leads to the other. (See also respiratory failure Acute Hypoxemic Respiratory Failure (AHRF, ARDS) Acute hypoxemic respiratory failure is severe arterial hypoxemia that is refractory to supplemental oxygen. It is caused by intrapulmonary shunting of blood resulting from airspace filling or... read more , dyspnea Dyspnea Dyspnea is unpleasant or uncomfortable breathing. It is experienced and described differently by patients depending on the cause. Although dyspnea is a relatively common problem, the pathophysiology... read more , and hypoxia Oxygen Desaturation Patients without respiratory disorders who are in the intensive care unit (ICU)—and other patients—may develop hypoxia (oxygen saturation < 90%) during a hospital stay. Hypoxia in patients... read more .)
(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 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 Infant Death Syndrome (SIDS) Sudden infant death syndrome is the sudden and unexpected death of an infant or young child between 2 weeks and 1 year of age in which an examination of the death scene, thorough postmortem... 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 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 ).
1. Atkins DL, Everson-Stewart S, Sears GK, et al; Resuscitation Outcomes Consortium Investigators: Epidemiology and outcomes from out-of-hospital cardiac arrest in children: the Resuscitation Outcomes Consortium Epistry-Cardiac Arrest. Circulation 119(11):1484–1491, 2009. doi: 10.1161/CIRCULATIONAHA.108.802678
2. Scheller RL, Johnson L, Lorts A, Ryan TD: Sudden cardiac arrest in pediatrics. Pediatr Emerg Care 32(9):630–636, 2016. doi: 10.1097/PEC.0000000000000895
3. Meert KL, Telford R, Holubkov R, et al; Therapeutic Hypothermia after Pediatric Cardiac Arrest (THAPCA) Trial Investigators: Pediatric out-of-hospital cardiac arrest characteristics and their association with survival and neurobehavioral outcome. Pediatr Crit Care Med 17(12):e543–e550, 2016. doi: 10.1097/PCC.0000000000000969
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.
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.
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":
H:Hypoxia, hypovolemia, acidosis (hydrogen ion), hyperkalemia or hypokalemia, hypothermia
T:Tablet or toxin ingestion, cardiac tamponade, tension pneumothorax, thrombosis (pulmonary 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 or coronary)
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 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 diaphoresis.... read more (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
Early and effective bystander-initiated CPR
In-hospital location (particularly a monitored unit)
Initial rhythm of 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) or 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)
Early defibrillation of VF or VT
Postresuscitative care, including circulatory support and access to cardiac catheterization
In adults, targeted temperature management (body temperature of 32 to 36° C) and avoidance of hyperthermia (1, 2 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.
1. Bernard SA, Gray TW, Buist MD, et al: Treatment of comatose survivors of out-of-hospital cardiac arrest with induced hypothermia. N Engl J Med 346:557–563, 2002. doi 10.1056/NEJMoa003289
2. Nielsen N, Wetterslev J, Cronberg T, et al: Targeted temperature management at 33°C versus 36°C after cardiac arrest. N Engl J Med 369:2197–2206, 2013. doi: 10.1056/NEJMoa1310519
Rapid defibrillation for shockable rhythms (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] or 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])
Early administration of epinephrine for nonshockable rhythms
When possible, treatment of primary cause
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 ).
1. Moler FW, Silverstein FS, Holubkov R, et al: Therapeutic hypothermia after in-hospital cardiac arrest in children. N Engl J Med 376:318–332, 2017. doi: 10.1056/NEJMoa1610493
2. Moler FW, Silverstein FS, Holubkov R, et al: Therapeutic hypothermia after out-of-hospital cardiac arrest in children. N Engl J Med 372:1898–1908, 2015. doi: 10.1056/NEJMoa1411480
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.
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