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 (sometimes without warning). Sudden cardiac arrest occurs outside the hospital in more than 350,000 people/year in the US, with a 90% mortality.
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 read more .)
(See also the American Heart Association's 2018 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, but especially coronary artery disease Overview of Coronary Artery Disease Coronary artery disease (CAD) involves impairment of blood flow through the coronary arteries, most commonly by atheromas. Clinical presentations include silent ischemia, angina pectoris, acute... read more ). 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 sudden cardiac arrest are less common than in adults. The predominant cause of sudden cardiac arrest in infants and children is respiratory failure due to various respiratory disorders (eg, airway obstruction, smoke inhalation, 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 ). Other causes of sudden cardiac arrest include trauma and poisoning.
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.
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.
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 (PEA, or 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, hypoglycemia
T:Tablet or toxin ingestion, cardiac tamponade, tension pneumothorax, thrombosis (pulmonary embolus 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 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 ), trauma
Unfortunately, many causes are not identified during cardiopulmonary resuscitation (CPR). Clinical examination, chest ultrasonography, and chest x-ray can detect 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 . 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 (MI) 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 . Rapid bedside blood tests can detect abnormal levels of potassium or glucose. 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 VF or VT
Early defibrillation (of VT or VF after initial chest compression)
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 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 , 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 ICU or emergency department), about 50% of adults survive to hospital discharge. Overall, in-hospital arrest (VT/VF and asystole/PEA) survival is about 25%.
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 10%.
Only about 10% of all cardiac arrest survivors have good central nervous system function 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 intervention is essential.
(See also the American Heart Association's 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 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 sudden 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 they improve 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 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 , 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
Drugs Mentioned In This Article
|Drug Name||Select Trade|
|No US brand name|