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| {{DiseaseDisorder infobox |
| | #redirect:[[Sudden cardiac death#Cardiac arrest]] |
| Name = Cardiac arrest |
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| ICD10 = {{ICD10|I|46||i|30}} |
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| ICD9 = {{ICD9|427.5}} |
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| }}
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| [[Image:Checking respiration2.jpg|thumb|160px|Checking respiration.]]
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| [[Image:Carotidian pulse.png|thumb|160px|Checking carotid pulse.]] | |
| [[Image:Insulfation2.jpg|thumb|160px|Insulfation ''mouth-to-mouth''.]]
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| {{SI}}
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| {{CMG}}
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| {{EH}}
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| ==Overview==
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| A '''cardiac arrest''', also known as '''cardiorespiratory arrest''', '''cardiopulmonary arrest''' or '''circulatory arrest''', is the abrupt cessation of normal circulation of the [[blood]] due to failure of the [[heart]] to contract effectively during [[Systole (medicine)|systole]].<ref name="Harrison"> [http://books.mcgraw-hill.com/medical/harrisons/ Harrison's Principles of Internal Medicine] 16th Edition, The McGraw-Hill Companies, ISBN 0-07-140235-7</ref>
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| "Arrested" blood circulation prevents delivery of [[oxygen]] to ''all'' parts of the body. Cerebral [[hypoxia (medical)|hypoxia]], or lack of oxygen supply to the brain, causes victims to [[unconsciousness|lose consciousness]] and to [[respiratory arrest|stop normal breathing]]. Brain injury is likely if cardiac arrest is untreated for more than 5 minutes,<ref name="pmid3536160">{{cite journal |author=Safar P |title=Cerebral resuscitation after cardiac arrest: a review |journal=Circulation |volume=74 |issue=6 Pt 2 |pages=IV138–53 |year=1986 |month=December |pmid=3536160 |doi= |url=}}</ref> To improve survival and neurological recovery immediate response is paramount.<ref name="IrwinRippe"> [http://www.lww.com/product/?0-7817-3548-3 Irwin and Rippe's Intensive Care Medicine] by Irwin and Rippe, Fifth Edition (2003), Lippincott Williams & Wilkins, ISBN 0-7817-3548-3</ref>
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| Cardiac arrest is a [[medical emergency]] that, in certain groups of [[patient]]s, is potentially reversible if treated early enough (See Reversible Causes, below). When unexpected cardiac arrest leads to death this is called '''[[sudden cardiac death]]''' (SCD)<ref name="Harrison"> [http://books.mcgraw-hill.com/medical/harrisons/ Harrison's Principles of Internal Medicine] 16th Edition, The McGraw-Hill Companies, ISBN 0-07-140235-7</ref>. The primary first-aid treatment for cardiac arrest is ''[[cardiopulmonary resuscitation]]'' (commonly known as '''CPR''') to provide circulatory support until availability of definitive medical treatment, which will vary dependant on the rhythm the heart is exhibiting, but often requires [[defibrillation]].
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| ==Characteristics & Diagnosis==
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| Cardiac Arrest is an abrupt cessation of pump function (evidenced by absence of a palpable pulse) of the heart that with prompt intervention could be reversed, but without it will lead to death.<ref name="Harrison"> [http://books.mcgraw-hill.com/medical/harrisons/ Harrison's Principles of Internal Medicine] 16th Edition, The McGraw-Hill Companies, ISBN 0-07-140235-7</ref>
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| Due to inadequate cerebral perfusion, the patient will be [[unconscious]] and will have stopped [[breath]]ing. 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.
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| In many cases, lack of [[pulse|carotid pulse]] is the [[gold standard (test)|gold standard]] for diagnosing cardiac arrest, but lack of a pulse (particularly in the peripheral pulses) may be a result of other conditions (e.g. [[shock]]), or simply an error on the part of the rescuer. Studies have shown that rescuers often make a mistake when checking the carotid pulse in an emergency, whether they are healthcare professionals<ref>Flesche CW, Breuer S, Mandel LP, Breivik H, Tarnow J. (1994) The ability of health professionals to check the carotid pulse. ''Circulation'' Vol. 90: I–288.</ref><ref name="pmid9715777">{{cite journal |author=Ochoa FJ, Ramalle-Gómara E, Carpintero JM, García A, Saralegui I |title=Competence of health professionals to check the carotid pulse |journal=Resuscitation |volume=37 |issue=3 |pages=173–5 |year=1998 |month=June |pmid=9715777 |doi= |url=http://linkinghub.elsevier.com/retrieve/pii/S0300957298000550}}</ref> or lay persons.<ref name="pmid9259056">{{cite journal |author=Bahr J, Klingler H, Panzer W, Rode H, Kettler D |title=Skills of lay people in checking the carotid pulse |journal=Resuscitation |volume=35 |issue=1 |pages=23–6 |year=1997 |month=August |pmid=9259056 |doi= |url=http://linkinghub.elsevier.com/retrieve/pii/S0300957296010921}}</ref>
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| 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,<ref name="pmid16314375">{{cite journal |author= |title=2005 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care |journal=Circulation |volume=112 |issue=24 Suppl |pages=IV1–203 |year=2005 |month=December |pmid=16314375 |doi=10.1161/CIRCULATIONAHA.105.166550 |url=}}</ref> 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]].<ref name="RCUK2005">Resuscitation Council UK (2005). ''Resuscitation Guidelines 2005'' London: Resuscitation Council UK.</ref>
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| Various other methods for detecting circulation have been proposed. Guidelines following the 2000 International Liaison Committee on Resusciation (ILCOR) recommendations were for rescuers to look for "signs of circulation", but not specifically the pulse <ref name="pmid16314375">{{cite journal |author= |title=2005 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care |journal=Circulation |volume=112 |issue=24 Suppl |pages=IV1–203 |year=2005 |month=December |pmid=16314375 |doi=10.1161/CIRCULATIONAHA.105.166550 |url=}}</ref>. These signs included coughing, gasping, colour, twitching and movement.<ref> St John Ambulance, St Andrew's Ambulance Association, British Red Cross (2002) (8th Ed.) ''First Aid Manual''. London: Dorling Kindersley </ref> 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.<ref name="pmid16314375">{{cite journal |author= |title=2005 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care |journal=Circulation |volume=112 |issue=24 Suppl |pages=IV1–203 |year=2005 |month=December |pmid=16314375 |doi=10.1161/CIRCULATIONAHA.105.166550 |url=}}</ref>
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| Following initial diagnosis of cardiac arrest, healthcare professionals further categorise the diagnosis based on the [[Electrocardiogram|ECG/EKG]] rhythm. There are 4 rhythms which result in a cardiac arrest. [[Ventricular fibrillation]] (VF/VFib) and Pulseless [[Ventricular tachycardia]] (VT) are both responsive to a [[defibrillator]] and so are colloquially referred to as "Shockable" rhythms, whereas [[Asystole]] and [[Pulseless electrical activity|Pulseless Electrical Activity]] (PEA) are non-shockable. The nature of the presenting hearth rhythm suggests different causes and treatment, and is used to guide the rescuer as to what treatment may be appropriate<ref name="RCUK2005">Resuscitation Council UK (2005). ''Resuscitation Guidelines 2005'' London: Resuscitation Council UK.</ref> (see [[Advanced Life Support]] and [[Advanced Cardiac Life Support]], as well as the causes of arrest (below))
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| ==Causes of Cardiac Arrest==
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| Cardiac arrest is synonymous with [[Clinical death]]. All disease processes leading to death have a period of (potentially) reversible cardiac arrest: the causes of arrest are, therefore, numerous. However, many of these conditions, rather than causing an arrest themselves, promote one of the "reversible causes" (see below), which then triggers the arrest (e.g. [[Choking]] leads to [[Hypoxia]] which in turn leads to an arrest). In some cases, the underlying mechanism cannot be overcome, leading to an unsuccessful resuscitation.
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| Among adults, [[ischemic heart disease]] is the predominant cause of arrest.<ref name="pmid11320390">{{cite journal |author=Eisenberg MS, Mengert TJ |title=Cardiac resuscitation |journal=N. Engl. J. Med. |volume=344 |issue=17 |pages=1304–13 |year=2001 |month=April |pmid=11320390 |doi= |url=http://content.nejm.org/cgi/pmidlookup?view=short&pmid=11320390&promo=ONFLNS19}}</ref> At [[autopsy]] 30% of victims show signs of recent [[myocardial infarction]]. Other cardiac conditions potentially leading to arrest include structural abnormalities, arrhythmias and cardiomyopathies. Non-cardiac causes include infections, overdoses, trauma and cancer, in addition to many others.
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| ===Reversible causes===
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| [[Cardiopulmonary resuscitation]] (CPR), including adjunctive measures such as defibrillation, intubation and drug administration, is the standard of care for initial treatment of cardiac arrest. However, most cardiac arrests occur for a reason, and unless that reason can be found and overcome, CPR is often ineffective, or if it does result in a return of spontaneous circulation, this is short lived. <ref name="RCUK2005">Resuscitation Council UK (2005). ''Resuscitation Guidelines 2005'' London: Resuscitation Council UK.</ref>. As highlighted above, a variety of disease processes can lead to a cardiac arrest, however they usually boil down to one or more of the "Hs and Ts" (see below).
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| ====H's====
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| * [[Hypovolemia|'''H'''ypovolemia]] - A lack of circulating [[body fluids]], principally [[blood]] volume. This is usually (though not exclusively) caused by some form of [[bleeding]], [[anaphylaxis]], or [[pregnancy]] with gravid uterus. [[Cardiac arrest#Peri-arrest period|Peri-arrest treatment]] includes giving [[Intravenous therapy|IV fluids]] and [[blood transfusions]], and controlling the source of any [[bleeding]] - by direct pressure for external bleeding, or emergency surgical techniques such as [[esophagogastroduodenoscopy]] (i.e. [[esophageal varices]]) and [[thoracotomy]] for internal bleeding.
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| * [[Hypoxia|'''H'''ypoxia]] - A lack of [[oxygen]] to the [[heart]], [[brain]] and other [[vital organ]]s. This can be identified through a careful assessment of breath sounds and tuble placement. Treatment may include providing oxygen, proper ventilation, and good [[cardiopulmonary resuscitation|CPR]] technique.
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| * [[Hydrogen|'''H'''ydrogen]] ions ([[Acidosis]]) - An abnormal pH in the body as a result of shock, [[Diabetic ketoacidosis]], [[renal failure]], or [[tricyclic antidepressant]] overdose. This can be treated with proper ventilation, good [[cardiopulmonary resuscitation|CPR]] technique, and buffers like [[sodium bicarbonate]].
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| * [[Hyperkalemia|'''H'''yperkalemia]] or [[Hypokalemia|'''H'''ypokalemia]] - The most life threatening [[electrolyte]] derangement is [[hyperkalemia]] (too much potassium). The classic presentation is the [[chronic renal failure]] patient who has missed a [[dialysis]] appointment and presents with [[weakness]], [[nausea]], and broad [[QRS complex]]es on the [[electrocardiogram]]. The most important initial therapy is the administration of [[calcium]], either with [[calcium gluconate]] or [[calcium chloride]]. Other therapies may include nebulized [[albuterol]], [[sodium bicarbonate]], [[glucose]], and [[insulin]]. The diagnosis of [[hypokalemia]] (not enough [[potassium]]) can be suspected when there is a history of [[diarrhoea]] or [[malnutrition]]. Loop [[diuretic]]s may also contribute. The [[electrocardiogram]] may show depressed T waves and prominent U waves. [[Hypokalemia]] is an important cause of acquired [[long QT syndrome]], and may predispose the patient to [[torsades de pointes]]. [[Digitalis]] use may increase the risk that [[hypokalemia]] will produce life threatening [[arrhythmia]]s.
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| * [[Hypothermia|'''H'''ypothermia]] - A low [[body temperature|core body temperature]], defined clinically as a [[temperature]] of less than 35 degrees Celsius. The patient is re-warmed either by using a [[heart-lung machine|cardiac bypass]] or by irrigation of the body cavities (such as thorax, peritoneum, bladder) with warm fluids; or warmed [[IV]] fluids. [[CPR]] only is given until the core body temperature reached 30 degrees Celsius, as [[defibrillation]] is ineffective at lower temperatures. Patients have been known to be successfully resuscitated after periods of hours in hypothermia and cardiac arrest, and this has given rise to the often-quoted medical truism, "You're not dead until you're warm and dead."
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| * [[Hypoglycemia|'''H'''ypoglycemia]] or [[Hyperglycemia|'''H'''yperglycemia]] - Low blood glucose from insulin reactions, [[diabetic ketoacidosis|DKA]], [[nonketotic hyperosmolar coma]]. This condition can be suspected when the patient is known to be a [[diabetic]]. The treatment may include fluids, [[potassium]], [[glucose]] (for hypoglycemia), and [[insulin]] (for hyperglycemia).
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| ====T's====
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| * [[Tablets|'''T'''ablets]] or [[Toxins|'''T'''oxins]] - [[Tricyclic antidepressant]]s, [[phenothiazines]], [[beta blocker]]s, [[calcium channel blocker]]s, [[cocaine]], [[digoxin]], [[aspirin]], [[acetominophen]]. This may be evidenced by items found on or around the patient, the patient's medical history (i.e. drug abuse, medication) taken from family and friends, checking the [[medical records]] to make sure no interacting drugs were prescribed, or sending [[blood]] and [[urine]] samples to the [[toxicology]] lab for report. Treatment may include specific [[antidote]]s, fluids for volume expansion, vasopressors, [[sodium bicarbonate]] (for [[tricyclic antidepressant]]s), [[glucagon]] or [[calcium]] (for [[calcium channel blocker]]s), [[benzodiazepine]]s (for [[cocaine]]), or [[cardiopulmonary bypass]].
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| * [[Cardiac tamponade|Cardiac '''T'''amponade]] - Blood or other fluids building up in the [[pericardium]] can put pressure on the heart so that it is not able to beat. This condition can be recognized by the presence of a narrowing [[pulse pressure]], muffled [[heart sounds]], distended neck veins, [[electrical alternans]] on the [[electrocardiogram]], or [[echocardiogram]]. This is treated in an emergency by inserting a needle into the [[pericardium]] to drain the fluid ([[pericardiocentesis]]), or if the fluid is too thick then an emergency [[thoracotomy]] is performed to cut the pericardium and release the fluid.
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| * [[Tension pneumothorax|'''T'''ension pneumothorax]] - The build up of air into one of the [[pleural cavity|pleural cavities]], which causes a [[mediastinum|mediastinal]] shift. When this happens, the [[great vessels]] (particularly the [[superior vena cava]]) become kinked, which limits [[blood]] return to the [[heart]]. The condition can be recognized by severe air hunger, [[hypoxia]], jugular venous distension, hyperressonance to percussion on the effected side, and a tracheal shift away from the effected side. The tracheal shift often requires a chest [[x-ray]] to appreciate. This is relieved in an emergency by a needle [[thoracotomy]] (inserting a needle catheter) into the 2nd [[intercostal space]] at the mid-[[clavicle|clavicular]] line, which relieves the pressure in the [[pleural cavity]].
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| * [[Thrombosis|'''T'''hrombosis]] ([[Myocardial infarction]]) - If the patient can be successfully resuscitated, there is a chance that the [[myocardial infarction]] can be treated, either with [[thrombolysis|thrombolytic therapy]] or [[percutaneous coronary intervention]].
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| * [[Thrombosis|'''T'''hromboembolism]] ([[Pulmonary embolism]]) - Usually diagnosed at autopsy. Patients in [[asystole]] or [[pulseless electrical activity]] have a poor prognosis. If this can be detected early, the patient may receive [[dopamine]], [[heparin]], and [[thrombolytic]]s.
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| * [[Physical trauma|'''T'''rauma]] ([[Hypovolemia]]) - Reduced blood volume from acute injury or primary damage to the [[heart]] or [[great vessels]]. Cardiac arrest secondary to [[Physical trauma|trauma]], particularly [[blunt trauma]], has a very poor [[prognosis]].
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| ==Treatment==
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| ===Out of hospital arrest===
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| Most out-of-hospital cardiac arrests occur following a [[Myocardial infarction]] (heart attack), and present initially with a heart rhythm of [[Ventricular fibrillation]]. The patient is therefore likely to be responsive to [[defibrillation]], and this has become the focus of pre-hospital interventions. Several organisations promote the idea of a "[[chain of survival]]", of which defibrillation is a key step. The links are:
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| * '''Early recognition''' - If possible, recognition of illness before the patient develops a cardiac arrest will allow the rescuer to prevent its occurrence. Early recognition that a cardiac arrest has occurred is key to survival - for every minute a patient is in cardiac arrest, their chances of survival drop by roughly 10% <ref name="RCUK2005">Resuscitation Council UK (2005). ''Resuscitation Guidelines 2005'' London: Resuscitation Council UK.</ref>
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| * '''Early [[Cardiopulmonary resuscitation|CPR]]''' - This buys time by keeping vital organs perfused with oxygen whilst waiting for equipment and trained personnel to reverse the arrest. In particular, by keeping the brain supplied with oxygenated blood, chances of neurological damage are decreased.
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| * '''Early defibrillation''' - This is the only effective for [[Ventricular fibrillation]], and also has benefit in [[Ventricular tachycardia]]<ref name = "RCUK2005"/>. If defibrillation is delayed, then the rhythm is likely to degenerate into [[Asystole]], for which outcomes are markedly worse.
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| * '''Early post-resuscitation care''' - Treatment and rehabillitation in a hospital by specialist staff helps to prevent further complications, attempts to fully reverse the underlying cause, and promotes quality of life.
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| If one or more links in the chain are missing or delayed, then the chances of survival drop significantly. In particular, bystander CPR is an important indicator of survival: if it has not been carried out, then resuscitation is associated with very poor results. Paramedics in some jurisdictions are authorised to abandon resuscitation altogether if the early stages of the chain have not been carried out in a timely fashion prior to their arrival.
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| Because of this, considerable effort has been put into educating the public on the need for CPR. In addition, there is increasing use of public access defibrillation. This involves placing [[Automated external defibrillator]]s in public places, and training key staff in these areas how to use them. This allows defibrillation to take place prior to the arrival of emergency services, and has been shown to lead to increased chances of survival. In addition, it has been shown that those who suffer arrests in remote locations have worse outcomes following cardiac arrest <ref name="pmid15333549">{{cite journal |author=Lyon RM, Cobbe SM, Bradley JM, Grubb NR |title=Surviving out of hospital cardiac arrest at home: a postcode lottery? |journal=Emerg Med J |volume=21 |issue=5 |pages=619–24 |year=2004 |month=September |pmid=15333549 |pmc=1726412 |doi=10.1136/emj.2003.010363 |url=}}</ref>: these areas often have [[First responder]] schemes, whereby members of the community receive training in resuscitation and are given a defibrillator, and called by the emergency medical services in the case of a collapse in their local area.
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| ===Hospital treatment===
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| Treatment within a hospital usually follows [[advanced life support]] protocols. Depending on the [[diagnosis]], various treatments are offered, ranging from [[defibrillation]] (for [[ventricular fibrillation]] or [[ventricular tachycardia]]) to [[surgery]] (for cardiac arrest which can be reversed by surgery - see causes of arrest, above) to [[medication]] (for [[asystole]] and [[pulseless electrical activity|PEA]]). All will include[[CPR]].
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| ===Peri-arrest period===
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| The period (either before or after) surrounding a cardiac arrest is known as the '''peri-arrest period'''. During this period the patient is in a highly unstable condition and must be constantly monitored in order to halt the progression or repeat of a full cardiac arrest. The [[preventative treatment]] used during the peri-arrest period depends on the causes of the impending arrest and the likelihood such an event occurring.
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| ==Prognosis==
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| The out-of-hospital cardiac arrest (OHCA) has a worse survival rate (2-8% at discharge and 8-22% on admission), than an in-hospital cardiac arrest (15% at discharge). The principal determining factor is the initially documented rhythm. Patients with VF/VT have 10-15 times more chance of surviving than those suffering from [[Pulseless electrical activity]] or [[Asystole]] (as they are sensitive to [[defibrillation]], whereas asystole and PEA are not).
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| Since mortality in case of OHCA is high, programs were developed to improve survival rate. A study by Bunch et al showed that, although mortality in case of ventricular fibrillation is high, rapid intervention with a [[defibrillator]] increases survival rate to that of patients that did not have a cardiac arrest.{{cite journal |author=Eisenberg MS, Mengert TJ |title=Cardiac resuscitation |journal=N. Engl. J. Med. |volume=344 |issue=17 |pages=1304–13 |year=2001 |month=April |pmid=11320390 |doi= |url=http://content.nejm.org/cgi/pmidlookup?view=short&pmid=11320390&promo=ONFLNS19}}</ref><ref name="pmid12826637">{{cite journal |author=Bunch TJ, White RD, Gersh BJ, ''et al'' |title=Long-term outcomes of out-of-hospital cardiac arrest after successful early defibrillation |journal=N. Engl. J. Med. |volume=348 |issue=26 |pages=2626–33 |year=2003 |month=June |pmid=12826637 |doi=10.1056/NEJMoa023053 |url=}}</ref>
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| Survival is mostly related to the cause of the arrest (see above). In particular, patients who have suffered [[hypothermia]] have an increased survival rate, possibly because the cold protects the vital organs from the effects of tissue hypoxia. Survival rates following an arrest induced by toxins is very much dependent on identifying the toxin and administering an appropriate antidote. A patient who has suffered a [[myocardial infarction]] due to a [[blood clot]] in the [[Left coronary artery]] has a lower chance of survival as it cuts of the blood supply to most of the left ventricle (the chamber which must pump blood to the whole of the systemic circulation).
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| Cobbe et al (1996) conducted a study into survival rates from out of hospital cardiac arrest. 14.6% of those who had received resuscitation by ambulance staff survived as far as admission to an acute hospital ward. Of these, 59.3% died during that admission, half of these within the first 24 hours. 46.1% survived to hospital discharge (this is 6.75% of those who had been resuscitated by ambulance staff), however 97.5% suffered a mild to moderate neurological disability, and 2% suffered a major neurological disability. Of those who were successfully discharged from hospital, 70% were still alive 4 years after their discharge.<ref name="pmid15333549">{{cite journal |author=Lyon RM, Cobbe SM, Bradley JM, Grubb NR |title=Surviving out of hospital cardiac arrest at home: a postcode lottery? |journal=Emerg Med J |volume=21 |issue=5 |pages=619–24 |year=2004 |month=September |pmid=15333549 |pmc=1726412 |doi=10.1136/emj.2003.010363 |url=}}</ref><ref name="pmid8664715">{{cite journal |author=Cobbe SM, Dalziel K, Ford I, Marsden AK |title=Survival of 1476 patients initially resuscitated from out of hospital cardiac arrest |journal=BMJ |volume=312 |issue=7047 |pages=1633–7 |year=1996 |month=June |pmid=8664715 |pmc=2351362 |doi= |url=http://bmj.com/cgi/pmidlookup?view=long&pmid=8664715}}</ref>
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| Ballew (1997) performed a review of 68 earlier studies into prognosis following in-hospital cardiac arrest. They found a survival to discharge rate of 14% (this roughly double the rate for out of hospital arrest found by Cobbe et al (see above)), although there was a wide range (0-28%).<ref name="pmid9167565">{{cite journal |author=Ballew KA |title=Cardiopulmonary resuscitation |journal=BMJ |volume=314 |issue=7092 |pages=1462–5 |year=1997 |month=May |pmid=9167565 |pmc=2126720 |doi= |url=http://bmj.com/cgi/pmidlookup?view=long&pmid=9167565}}</ref>
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| Several high profile organisations (such as [[St John Ambulance]] and the [[British Heart Foundation]]) have promoted the "Chain of Survival", which is made up of 4 links, as a way to maximise prognosis following arrest:
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| * Early Access - Identifying patients at risk of cardiac arrest early is the best way of improving prognosis, as it is often possible to prevent the arrest. Similarly, if the arrest is witnessed there is a much greater chance of survival, as treatment can begin straight away before tissue hypoxia sets in.
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| * Early [[CPR]] - CPR is unlikely to revive the patient, but it does buy some time by keeping a (limited) circulation going until it is possible to reverse the arrest, thereby increasing the chances of this reversal being successful, and minimising the risk of cerebral hypoxia (which can lead to neurological impairment following return of circulation).
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| * Early [[defibrillation]] - Patients who present with VF/VT can be defibrillated, and the earlier this happens the better, as VF/VT often degenerate into asystole (which is unshockable).
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| * Early [[hospital]] care - Many patients suffer further arrests within the first 24 hours of admission, so it is better that they are in hospital where their chances of survival are a little higher.
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| ==Prevention==
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| With positive outcomes following cardiac arrest so unlikely, a great deal of effort has been spent in finding effective strategies to prevent cardiac arrest.
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| As noted above, one of the prime causes of cardiac arrest outside of hospital is [[ischemic heart disease]]. Vast resources have been put into trying to reduce cardiovascular risks across much of the developed world. In particular schemes have been put in place to promote a [[healthy diet]] and [[exercise]]. For people considered to be particularly at risk of heart disease, measures such as [[blood pressure]] control, prescription of [[cholesterol]] lowering medications, and other medico-therapeutic interventions, have been widely used. A [[magnesium deficiency (medicine)|magnesium deficiency]], or lower levels of [[magnesium]], can contribute to heart disease and a [[healthy diet]] that contains adequte [[magnesium]] may help prevent heart disease.<ref name="pmid15466951">{{cite journal |author=Rosanoff A, Seelig MS |title=Comparison of mechanism and functional effects of magnesium and statin pharmaceuticals |journal=J Am Coll Nutr |volume=23 |issue=5 |pages=501S–505S |year=2004 |month=October |pmid=15466951 |doi= |url=http://www.jacn.org/cgi/pmidlookup?view=long&pmid=15466951}}</ref> [[Magnesium]] can be used to enhance long term treatment, so it may be effective in long term prevention.<p>
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| Patients in hospital are far less likely to have a cardiac arrest caused of primary cardiac origin, and hence present in Asystole or PEA, and have bleak outcomes. Extensive research has shown that patients in general wards often deteriorate for several hours or even days before a cardiac arrest occurs <ref name="pmid15325446">{{cite journal |author=Kause J, Smith G, Prytherch D, Parr M, Flabouris A, Hillman K |title=A comparison of antecedents to cardiac arrests, deaths and emergency intensive care admissions in Australia and New Zealand, and the United Kingdom--the ACADEMIA study |journal=Resuscitation |volume=62 |issue=3 |pages=275–82 |year=2004 |month=September |pmid=15325446 |doi=10.1016/j.resuscitation.2004.05.016 |url=}}</ref>. 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 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 risk which patients are at of deterioration based on their [[vital signs]] and thus provide a guide to staff. In addition, specialist staff are being utilised more effectively in order to augment the work already being done at ward level. These include:
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| * '''Crash teams''' (also known as '''Code teams''') - These are designated staff members who have particular expertise in resuscitation, who are called to the scene of all arrests within the hospital.
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| * '''Medical Emergency Teams''' - These teams respond to all emergencies, with the aim of treating the patient in the acute phase of their illness in order to prevent a cardiac arrest.
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| * '''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 unit|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.
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| ==Implantable cardioverter defibrillators==
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| A technically based intervention to prevent further cardiac arrest episodes is the use of an '''[[implantable cardioverter-defibrillator]]''' (ICD). This device is implanted in to the patient and can offer a 'pacemaker' effect to the heart as well as acting as an instant defibrillator in the event of arrhythmia. A recent study by Birnie et al at the University of Ottawa Heart Institute has demonstrated that ICDs are underused in both the United States and Canada.<ref name="pmid17606938">{{cite journal |author=Birnie DH, Sambell C, Johansen H, ''et al'' |title=Use of implantable cardioverter defibrillators in Canadian and US survivors of out-of-hospital cardiac arrest |journal=CMAJ |volume=177 |issue=1 |pages=41–6 |year=2007 |month=July |pmid=17606938 |pmc=1896034 |doi=10.1503/cmaj.060730 |url=}}</ref> An accompanying editorial by Simpson explores some of the economic, geographic, social and political reasons for this.<ref name="pmid17606939">{{cite journal |author=Simpson CS |title=Implantable cardioverter defibrillators work--so why aren't we using them? |journal=CMAJ |volume=177 |issue=1 |pages=49–51 |year=2007 |month=July |pmid=17606939 |pmc=1896028 |doi=10.1503/cmaj.070470 |url=}}</ref>
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| ==Ethical Issues==
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| [[Cardiopulmonary resuscitation]] and [[advanced cardiac life support]] are not always in a person's best interest. This is particularly true in the case of terminal illnesses when resuscitation will not alter the outcome of the disease. Properly performed CPR often fractures the [[rib]] cage, especially in older patients or those suffering from [[osteoporosis]]. [[Defibrillation]], especially repeated several times as called for by [[advanced cardiac life support|ACLS]] protocols, may also cause electrical burns.
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| Some people with a [[terminal illness]] choose to avoid such measures and die peacefully. People with views on the treatment they wish to receive in the event of a cardiac arrest should discuss these views with both their [[physician|doctor]] and with their family. A patient may ask their doctor to record a [[do not resuscitate]] (DNR) order in the medical record. Alternatively, in many jurisdictions, a person may formally state their wishes in an advance directive or [[advance health directive]].
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| ==See also==
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| * [[Asystole]]
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| * [[Clinical death]]
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| * [[Death]]
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| * [[Defibrillation]]
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| * [[Myocardial infarction]]
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| * [[Near-death experience]]
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| * [[Ventricular fibrillation]]
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| ==References==
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| {{Reflist|2}}
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| ==External links==
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| * [http://www.sca-aware.org Sudden Cardiac Arrest Foundation]
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| {{STEMI}}
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| {{Circulatory system pathology}}
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| {{SIB}}
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| [[da:Hjertestop]]
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| [[de:Kreislaufstillstand]]
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| [[es:Parada cardiorrespiratoria]]
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| [[fr:Arrêt cardio-circulatoire]]
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| [[id:Gagal jantung]]
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| [[it:Arresto cardiaco]]
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| [[he:דום לב]]
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| [[nl:Hartstilstand]]
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| [[ja:心停止]]
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| [[pt:Parada cardiorrespiratória]]
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| [[sv:Hjärtstillestånd]]
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| [[vi:Đột tử]]
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| [[pl:Asystolia]]
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| [[Category:Medical emergencies]]
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| [[Category:Causes of death]]
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| [[Category:Cardiology]]
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| [[Category:Emergency medicine]]
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| [[Category:Electrophysiology]]
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