Topic: Cardiac arrest,contents, Controls

Cardiac arrest is a sudden loss of blood flow resulting from the failure of the heart to effectively pump.[9] Symptoms include loss of consciousness and abnormal or absent breathing.[1][2] Some individuals may experience chest pain, shortness of breath, or nausea before cardiac arrest.[2] If not treated within minutes, it usually leads to death.[9]

The most common cause of cardiac arrest is coronary artery disease.[4] Less common causes include major blood loss, lack of oxygen, very low potassium, heart failure, and intense physical exercise.[4] A number of inherited disorders may also increase the risk including long QT syndrome.[4] The initial heart rhythm is most often ventricular fibrillation.[4] The diagnosis is confirmed by finding no pulse.[1] While a cardiac arrest may be caused by heart attack or heart failure, these are not the same.[9]

Prevention includes not smoking, physical activity, and maintaining a healthy weight.[5] Treatment for cardiac arrest include immediate cardiopulmonary resuscitation (CPR) and, if a shockable rhythm is present, defibrillation.[6] Among those who survive, targeted temperature management may improve outcomes.[10] An implantable cardiac defibrillator may be placed to reduce the chance of death from recurrence.[5]

In the United States, cardiac arrest outside hospital occurs in about 13 per 10,000 people per year (326,000 cases).[8] In hospital cardiac arrest occurs in an additional 209,000.[8] Cardiac arrest becomes more common with age.[3] It affects males more often than females.[3] The percentage of people who survive with treatment is about 8%.[7] Many who survive have significant disability.[7] Many U.S. television shows, however, have portrayed unrealistically high survival rates of 67%.[7]

Contents
1 Signs and symptoms
2 Causes
2.1 Coronary artery disease
2.2 Structural heart disease not related to CAD
2.3 Arrhythmias
2.4 Non-cardiac causes
2.5 Mnemonic for reversible causes
2.6 Risk factors
3 Mechanism
4 Diagnosis
4.1 Classifications
5 Prevention
5.1 Code teams
5.2 Implantable cardioverter defibrillator
5.3 Diet
6 Management
6.1 Cardiopulmonary resuscitation
6.2 Defibrillation
6.3 Medications
6.4 Targeted temperature management
6.5 Do not resuscitate
6.6 Chain of survival
6.7 Other
7 Prognosis
8 Epidemiology
9 Society and culture
9.1 Names
9.2 Show code
10 References
11 External links
Signs and symptoms
Cardiac arrest is preceded by no warning symptoms in approximately 50% of people.[11] For those who do, they have non specific symptoms, such as new or worsening chest pain, fatigue, blackouts, dizziness, shortness of breath, weakness, and vomiting.[12]

When the arrest occurs, the most obvious sign of its occurrence will be the lack of a palpable pulse in the person experiencing it (since the heart has ceased to contract, the usual indications of its contraction such as a pulse will no longer be detectable). Certain types of prompt intervention can often reverse a cardiac arrest, but without such intervention the event will almost always lead to death.[13] In certain cases, it is an expected outcome of a serious illness where death is expected.[14]

Also, as a result of inadequate blood flow to the brain (cerebral perfusion), the person will quickly become unconscious and will have stopped breathing. The main diagnostic criterion to diagnose a cardiac arrest (as opposed to respiratory arrest which shares many of the same features) is lack of circulation; however, there are a number of ways of determining this. Near-death experiences are reported by 10–20% of people who survived cardiac arrest.[15]

Causes:
Sudden cardiac arrest (SCA) and sudden cardiac death (SCD) occur when the heart abruptly begins to beat in an abnormal or irregular rhythm (arrhythmia). Without organized electrical activity in the heart muscle, there is no consistent contraction of the ventricles, which results in the heart's inability to generate an adequate cardiac output (forward pumping of blood from heart to rest of the body).[16] There are many different types of arrhythmias, but the ones most frequently recorded in SCA and SCD are ventricular tachycardia (VT) or ventricular fibrillation (VF).[17]

Sudden cardiac arrest can result from cardiac and non-cardiac causes including the following:

Coronary artery disease
Coronary artery disease (CAD), also known as ischemic heart disease, is responsible for 62 to 70 percent of all SCDs.[18][19] CAD is a much less frequent cause of SCD in people under the age of 40.[18]

Cases have shown that the most common finding at postmortem examination of sudden cardiac death (SCD) is chronic high-grade stenosis of at least one segment of a major coronary artery,[20] the arteries that supply the heart muscle with its blood supply.

Structural heart disease not related to CAD
Structural heart disease not related to CAD (i.e. hypertrophic cardiomyopathy, congenital coronary artery anomalies, myocarditis) account for 10% of all SCDs.[19][16] Examples of these include: cardiomyopathy, cardiac rhythm disturbances, myocarditis, hypertensive heart disease,[21] and congestive heart failure.[22]

Left ventricular hypertrophy is thought to be a leading cause of SCD in the adult population.[23] This is most commonly the result of longstanding high blood pressure which has caused secondary damage to the wall of the main pumping chamber of the heart, the left ventricle.[24]

A 1999 review of SCDs in the United States found that this accounted for over 30% of SCDs for those under 30 years. A study of military recruits age 18-35 found that this accounted for over 40% of SCDs.[18][19]

Congestive heart failure increases the risk of SCD fivefold.[22]

Arrhythmias
Arrhythmias not due to structural heart disease account for 5 to 10% of SCDs.[25][26][27]

Examples of arrhythmic syndromes associated with SCD include: Long QT syndrome, Wolff-Parkinson-White Syndrome, Brugada Syndrome, Catecholaminergic polymorphic ventricular tachycardia.[16]

Long QT syndrome, a condition often mentioned in young people's deaths, occurs in one of every 5000 to 7000 newborns and is estimated to be responsible for 3000 deaths each year compared to the approximately 300,000[28] cardiac arrests seen by emergency services. These conditions are a fraction of the overall deaths related to cardiac arrest, but represent conditions which may be detected prior to arrest and may be treatable.

Non-cardiac causes
SCA due to non-cardiac causes accounts for the remaining 15 to 25%.[27][29]

The most common non-cardiac causes are trauma, bleeding (such as gastrointestinal bleeding, aortic rupture, or intracranial hemorrhage), overdose, drowning and pulmonary embolism.[30] Cardiac arrest can also be caused by poisoning (for example, by the stings of certain jellyfish).

Mnemonic for reversible causes
Main article: Hs and Ts
"Hs and Ts" is the name for a mnemonic used to aid in remembering the possible treatable or reversible causes of cardiac arrest.[31][32]

Hs
Hypovolemia – A lack of blood volume
Hypoxia – A lack of oxygen
Hydrogen ions (Acidosis) – An abnormal pH in the body
Hyperkalemia or Hypokalemia – Both excess and inadequate potassium can be life-threatening.
Hypothermia – A low core body temperature
Hypoglycemia or Hyperglycemia – Low or high blood glucose
Ts
Tablets or Toxins
Cardiac Tamponade – Fluid building around the heart
Tension pneumothorax – A collapsed lung
Thrombosis (Myocardial infarction) – Heart attack
Thromboembolism (Pulmonary embolism) – A blood clot in the lung
Traumatic cardiac arrest
Risk factors
The risk factors for SCD are similar to those of coronary artery disease and include age, cigarette smoking, high blood pressure, high cholesterol, lack of physical exercise, obesity, diabetes, and family history.[33] A prior episode of sudden cardiac arrest also increases the risk of future episodes.[34]

Current cigarette smokers with coronary artery disease were found to have a two to threefold increase in the risk of sudden death between ages 30 and 59. Furthermore, it was found that former smokers risk was closer to that of those who had never smoked.[11][35]

Mechanism

Ventricular fibrillation
The mechanism of death in the majority of people dying of sudden cardiac death is ventricular fibrillation.[4] Structural changes in the diseased heart as a result of inherited factors (mutations in ion-channel coding genes for example) cannot explain the suddenness of SCD.[36] Also, sudden cardiac death could be the consequence of electric-mechanical disjunction and bradyarrhythmias.[37][38]

Diagnosis
Cardiac arrest is synonymous with clinical death. A cardiac arrest is usually diagnosed clinically by the absence of a pulse. In many cases lack of carotid pulse is the gold standard for diagnosing cardiac arrest, as lack of a pulse (particularly in the peripheral pulses) may result from other conditions (e.g. shock), or simply an error on the part of the rescuer. Nonetheless, studies have shown that rescuers often make a mistake when checking the carotid pulse in an emergency, whether they are healthcare professionals[39] or lay persons.[40]

Owing to the inaccuracy in this method of diagnosis, some bodies such as the European Resuscitation Council (ERC) have de-emphasised its importance. The Resuscitation Council (UK), in line with the ERC's recommendations and those of the American Heart Association,[41] have suggested that the technique should be used only by healthcare professionals with specific training and expertise, and even then that it should be viewed in conjunction with other indicators such as agonal respiration.[42]

Various other methods for detecting circulation have been proposed. Guidelines following the 2000 International Liaison Committee on Resuscitation (ILCOR) recommendations were for rescuers to look for "signs of circulation", but not specifically the pulse.[41] These signs included coughing, gasping, colour, twitching and movement.[43] However, in face of evidence that these guidelines were ineffective, the current recommendation of ILCOR is that cardiac arrest should be diagnosed in all casualties who are unconscious and not breathing normally.[41] Another method is to use molecular autopsy or postmortem molecular testing which uses a set of molecular techniques to find the ion channels that are cardiac defective.[citation needed]

Classifications
Clinicians classify cardiac arrest into "shockable" versus "non–shockable", as determined by the ECG rhythm. This refers to whether a particular class of cardiac dysrhythmia is treatable using defibrillation.[42] The two "shockable" rhythms are ventricular fibrillation and pulseless ventricular tachycardia while the two "non–shockable" rhythms are asystole and pulseless electrical activity.[44]

Prevention
With positive outcomes following cardiac arrest unlikely, an effort has been spent in finding effective strategies to prevent cardiac arrest. With the prime causes of cardiac arrest being ischemic heart disease, efforts to promote a healthy diet, exercise, and smoking cessation are important. For people at risk of heart disease, measures such as blood pressure control, cholesterol lowering, and other medico-therapeutic interventions are used.[1] A Cochrane review published in 2016 found moderate-quality evidence to show that blood pressure-lowering drugs do not appear to reduce sudden cardiac death.[45]

Code teams
In medical parlance, cardiac arrest is referred to as a "code" or a "crash". This typically refers to "code blue" on the hospital emergency codes. A dramatic drop in vital sign measurements is referred to as "coding" or "crashing", though coding is usually used when it results in cardiac arrest, while crashing might not. Treatment for cardiac arrest is sometimes referred to as "calling a code".

People in general wards often deteriorate for several hours or even days before a cardiac arrest occurs.[42][46] This has been attributed to a lack of knowledge and skill amongst ward-based staff, in particular a failure to carry out measurement of the respiratory rate, which is often the major predictor of a deterioration[42] and can often change up to 48 hours prior to a cardiac arrest. In response to this, many hospitals now have increased training for ward-based staff. A number of "early warning" systems also exist which aim to quantify the person's risk of deterioration based on their vital signs and thus provide a guide to staff. In addition, specialist staff are being used more effectively in order to augment the work already being done at ward level. These include:

Crash teams (or code teams) – These are designated staff members with particular expertise in resuscitation who are called to the scene of all arrests within the hospital. This usually involves a specialized cart of equipment (including defibrillator) and drugs called a "crash cart" or "crash trolley".
Medical emergency teams – These teams respond to all emergencies, with the aim of treating the people in the acute phase of their illness in order to prevent a cardiac arrest. These teams have been found to decrease the rates of in hospital cardiac arrest and improve survival.[8]
Critical care outreach – As well as providing the services of the other two types of team, these teams are also responsible for educating non-specialist staff. In addition, they help to facilitate transfers between intensive care/high dependency units and the general hospital wards. This is particularly important, as many studies have shown that a significant percentage of patients discharged from critical care environments quickly deteriorate and are re-admitted; the outreach team offers support to ward staff to prevent this from happening.[citation needed]
Implantable cardioverter defibrillator

Illustration of implantable cardioverter defibrillator (ICD)
An implantable cardioverter defibrillator (ICD) is a battery powered device that monitors electrical activity in the heart and when an arrhythmia or asystole is detected is able to deliver an electrical shock to terminate the abnormal rhythm. ICDs are used to prevent sudden cardiac death (SCD) in those that have survived a prior episode of sudden cardiac arrest (SCA) due to ventricular fibrillation or ventricular tachycardia (secondary prevention).[47] ICDs are also used prophylactically to prevent sudden cardiac death in certain high risk patient populations (primary prevention).[48]

Numerous studies have been conducted on the use of ICDs for the secondary prevention of SCD. These studies have shown improved survival with ICDs compared to the use of anti-arrhythmic drugs.[47] ICD therapy is associated with a 50% relative risk reduction in death caused by an arrhythmia and a 25% relative risk reduction in all cause mortality.[49]

Primary prevention of SCD with ICD therapy for high risk patient populations has similarly shown improved survival rates in a number of large studies. The high risk patient populations in these studies were defined as those with severe ischemic cardiomyopathy (determined by a reduced left ventricular ejection fraction (LVEF)). The LVEF criteria used in these trials ranged from less than or equal to 30% in MADIT-II to less than or equal to 40% in MUSTT.[47][48]

Diet
Marine-derived omega-3 polyunsaturated fatty acids (PUFAs) has been promoted for the prevention of sudden cardiac death due to its postulated ability to lower triglyceride levels, prevent arrhythmias, decrease platelet aggregation, and lower blood pressure.[50] However, according to a recent systematic review, omega-3 PUFA supplementation are not being associated with a lower risk of sudden cardiac death.[51]

Management
Sudden cardiac arrest may be treated via attempts at resuscitation. This is usually carried out based upon basic life support (BLS)/advanced cardiac life support (ACLS),[41] pediatric advanced life support (PALS)[52] or neonatal resuscitation program (NRP) guidelines.

Cardiopulmonary resuscitation
Cardiopulmonary resuscitation (CPR) is a key part of the management of cardiac arrest. It is recommended that it be started as soon as possible and interrupted as little as possible. The component of CPR that seems to make the greatest difference in most cases is the chest compressions. Correctly performed bystander CPR has been shown to increase survival; however, it is performed in less than 30% of out of hospital arrests as of 2007.[53] If high-quality CPR has not resulted in return of spontaneous circulation and the person's heart rhythm is in asystole, discontinuing CPR and pronouncing the person's death is reasonable after 20 minutes.[54] Exceptions to this include those with hypothermia or who have drowned.[54] Longer durations of CPR may be reasonable in those who have cardiac arrest while in hospital.[55] Bystander CPR, by the lay public, before the arrival of EMS also improves outcomes.[8]

Either a bag valve mask or an advanced airway may be used to help with breathing.[56] High levels of oxygen are generally given during CPR.[56] Tracheal intubation has not been found to improve survival rates in cardiac arrest[53] and in the prehospital environment may worsen it.[57] When done by EMS 30 compressions followed by two breaths appear better than continuous chest compressions and breaths being given while compressions are ongoing.[58]

For bystanders, CPR which involves only chest compressions results in better outcomes as compared to standard CPR for those who have gone into cardiac arrest due to heart issues.[58] Mechanical chest compressions (as performed by a machine) are no better than chest compressions performed by hand.[56] It is unclear if a few minutes of CPR before defibrillation results in different outcomes than immediate defibrillation.[59] If cardiac arrest occurs after 20 weeks of pregnancy someone should pull or push the uterus to the left during CPR.[60] If a pulse has not returned by four minutes emergency Cesarean section is recommended.[60]

By: Bluemoon

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