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| {{SI}}
| | #redirect:[[Anoxic brain injury]] |
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| {{CMG}}
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| '''Associate Editors-In-Chief:''' [[Varun Kumar]], M.B.B.S.; [[Lakshmi Gopalakrishnan]], M.B.B.S.
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| ==Predictors of Survival==
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| ===Improved Prognosis with In-Hospital versus Out-of-Hospital Cardiac Arrest===
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| Out-of-hospital cardiac arrest (OHCA) has a worse survival rate (8-22% on admission resulting in 2-8% at hospital discharge) than in-hospital cardiac arrest (15% at discharge).
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| ===Improved Prognosis with VT/VF versus PEA or Asystole===
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| A major determining factor in survival is the initially documented rhythm. Patients with [[ventricular fibrilation]] ([[VF]]) or [[ventricual tachycardia]] ([[VT]]) (aka VT/VF) have a 10-15 fold greater chance of survival than patients with [[pulseless electrical activity]] ([[PEA]]) or [[asystole]]. VT/VF are sensitive to [[defibrillation]], whereas asystole and PEA are not.
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| ===Rapid Defibrillation is Associated with Imporved Survival===
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| Rapid intervention with a [[defibrillator]] increases survival rates.<ref>{{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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| ===Role of Pre-Hospital Ambulance Care===
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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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| ==Incidence and Predictors of Entering Into a Vegetative State versus Making a Full Recovery==
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| Cardiac arrest is the third leading cause of [[coma]]. Approximately 80% of patients who suffered a cardiac arrest who survived to be admitted to the hospital will be in coma for varying lengths of time. Of these patients, approximately 40% will enter into a persistent vegetative state and 80% die within 1 year. in contrast, if a patient survives until discharge without significant neurological impairment, he/she can expect a fair to good quality of life.
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| The duration of hypoxia/ischemia determines the extent of neuronal injury i.e. in patients who suffer hypoxia for less than 5 minutes, are less likely to have permanent neurologic deficits, while with prolonged, global hypoxia, patients may develop [[myoclonus]] or a persistent [[vegetative state]].<ref name="pmid16363390">{{cite journal |author=Mellion ML |title=Neurologic consequences of cardiac arrest and preventive strategies |journal=[[Medicine and Health, Rhode Island]] |volume=88 |issue=11 |pages=382–5 |year=2005 |month=November |pmid=16363390 |doi= |url=}}</ref>
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| Thomassen A and Wernberg M conducted a study into prevalence and prognostic significance of coma after cardiac arrest outside intensive care and coronary units where 181 patients resuscitated from cardiac arrest were reviewed. In patients who suffered cardiac arrest outside hospital, 84% were comatose for more than 1hour and 56% for more than 24 hours. There was no significant neuronal damage if coma lasted less than 24hours. However, in patients who were comatose for more than 24 hours, had a bad prognosis. Of the patients reviewed, 85 remained comatose for more than 24hours and only 7 of them were discharged alive, but with severe neurological impairment with severity increasing with duration of coma. Of the patients who were in coma for more than 7days, none regained consciousness and 80 patients died in coma.<ref name="pmid442945">{{cite journal |author=Thomassen A, Wernberg M |title=Prevalence and prognostic significance of coma after cardiac arrest outside intensive care and coronary units |journal=[[Acta Anaesthesiologica Scandinavica]] |volume=23 |issue=2 |pages=143–8 |year=1979 |month=April |pmid=442945 |doi= |url=}}</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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| ==Systematic Efforts to Improve Survival Following Cardiac Arrest: The Chain of Survival==
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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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| ==References==
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| {{reflist|2}}
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| [[Category:Cardiology]]
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| [[Category:Emergency medicine]]
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| {{WH}}
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| {{WS}}
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