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| ==Prognosis==
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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 (2-8% survival at discharge) than in-hospital cardiac arrest (15% survival 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 electrocardiographic 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 and VF are responsive to [[defibrillation]], whereas asystole and PEA are not.
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| ====Rapid Defibrillation is Associated with Improved 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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| ===Incidence and Predictors of Entering Into a Vegetative State versus Making a Full Neurologic 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, those rare patients who survive until discharge without significant neurological impairment 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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| The duration of coma is an important predictor of the recovery of neurologic function. In a 1979 study of 181 cardiac arrest patients who survived to hospital admission, 84% were comatose for more than 1 hour and 56% were comatose for more than 24 hours<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>. There was minimal neurologic deficit if coma lasted less than 24 hours. However, among the 85 patients who were comatose for more than 24 hours, only 7 of them were discharged alive. The severity of neurological impairment increased with increased duration of coma. Of the patients who were in coma for more than 7 days, none regained consciousness. It should be noted that 80 patients died in a coma.
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| A [http://jama.ama-assn.org/content/253/10/1420.full.pdf+html JAMA article] in 1985 attempted to identify the multivariate predictors neurologic prognosis in 210 patients with coma due to cerebral hypoxia. A total of 13% of patients regained neurologic function and independent function at some time during the first year.
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| '''Initial Neurologic Findings:'''
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| * Patients who had the initial absence of pupillary light reflexes did not recover independent functioning (52 patients, 25% of patients)<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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| * In contrast, patients who had the initial presence of pupillary light reflexes, the development of spontaneous eye movements that were roving conjugate or better, and the presence of either extensor, flexor, or withdrawal responses to pain had a 41% chance of regaining independent function (of the 27 patients in this group, 11 (41%) regained independence).<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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| * In a study by Snyder et al, the absence of corneal or pupillary light reflexes at 3 hours after [[cardiac arrest]] was associated with death in all patients <ref>Snyder BD, Loewenson RB, Gumnit RJ, et al: Neurologic prognosis after cardiopulmonary arrest: II. Level of consciousness. Neurology 1980;30:52-58.</ref><ref>Snyder BD, Gumnit RJ, Leppik IE, et al: Neurologic prognosis after cardiopulmonary arrest: IV. Brainstem refl exes. Neurology 1981;31: 1092-1097</ref>. By 6 hours, all the patients who survived had the presence of three brainstem reflexes: [[pupillary light response]], [[corneal reflex]], and reflex eye movements.
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| *The absence of spontaneous limb movements and the absence of withdrawal to pain in the early hours is a poor prognostic sign.
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| *The presence of either decorticate or decerebrate posturing is a poor prognostic sign.
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| *Frequent [[myoclonic jerking]] is associated with a poor prognosis.
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| *The presence of seizures in the initial 24 hours is modestly associated with outcomes: 53% of patients who seize survive compared to 70% of those who do not seize during the first day<ref>Roine RO: Neurological Outcome of Out-of-Hospital Cardiac Arrest [dissertation]. University of Helsinki, 1993.</ref>.
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| '''24 Hour Neurologic Findings:'''
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| * Most patients who survive become alert by 24-48 hours. In one series, of those patients who were in a coma through day 2, only 2 of the 27 (7%) survived.<ref>Snyder BD, Loewenson RB, Gumnit RJ, et al: Neurologic prognosis after cardiopulmonary arrest: II. Level of consciousness. Neurology 1980;30:52-58.</ref> In a second series, no patient who remained in a coma by the third day sirvived.<ref>Bell JA, Hodgson HJF: Coma after cardiac arrest. Brain 1974;97:361-372.</ref>
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| * Absent motor responses, the presence of posturing (extensor / flexor motor responses) and the lack of spontaneous eye movements that were either orienting or roving conjugate was associated with a lack of independent recovery in 92 of 93 patients. <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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| * In contrast, of the 30 patients who showed improvement in their eye-opening responses, obeyed commands or had withdraw to pain, 19 (63%) regained independent function.<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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| *Seizures that occur after the initial 24 hours are associated with a poorer outcomes. In one study only 3 of 15 patients who seized recovered consciousness, and only one patient lived a year<ref>Roine RO: Neurological Outcome of Out-of-Hospital Cardiac Arrest [dissertation]. University of Helsinki, 1993.</ref>. The presence of [[status epilepticus]] at any time following cardiac arrest is associated with a very poor prognosis as all nine patients with status epilepticus died in one series.<ref>Roine RO: Neurological Outcome of Out-of-Hospital Cardiac Arrest [dissertation]. University of Helsinki, 1993.</ref>
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| *The absence of spontaneous eye opening and intermittent visual fixation by the end of the first day is associated with a poor prognosis. Although eye opening is necessary for a good outcomes, it alone is not sufficient, as many patients who have spontaneous eye opening still go on to have a poor prognosis. Roving eye movements in the absence of visual fixation is often indicative of extensive bilateral cerebral hemispheral damage and portends a poor prognosis. If the gaze is sustained in an upeard direction, this carries a poor prognosis as well.<ref>Keane JR: Sustained upgaze in coma. Annals of Neurolology 1981;9:409-412.</ref>
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| ==References== | | ==References== |