services personnel; no AED used or manual shock applied in out-of-hospital setting; and no ROSC in out-of-hospital setting [83]. The advanced life support (ALS) rule includes the BLS criteria as well as two additional criteria: arrest not witnessed by bystander and no bystander- administered CPR [84]. Validation of the predictive value of the BLS and ALS termination rules was performed with data from a retrospective cohort study that included 5505 adults with out-of-hospital SCA [85]. The overall rate of survival to hospital discharge was 7 percent. Of 2592 patients (47 percent) who met BLS criteria for termination of resuscitation efforts, only 5 survived to hospital discharge. Of 1192 patients (22 percent) who met ALS criteria, none survived to hospital discharge. However, the validity of these termination rules may be reduced with improvements in EMS and postresuscitation care. One potential target for understanding and ameliorating current limitations to postarrest care is the observed marked regional variation in prognosis following SCA. (See 'Prognosis following sudden cardiac arrest' above.) Adequacy of CPR The adequacy of CPR delivered to a victim of cardiac arrest and outcomes related to resuscitation efforts may depend on a variety of factors (eg, rate and depth of chest compressions, amount of time without performing chest compressions while performing other tasks such as defibrillation, etc). The American Heart Association (AHA) 2010 Guidelines for Cardiopulmonary Resuscitation (CPR) and Emergency Cardiovascular Care emphasized early defibrillation (when available) and high-quality chest compressions (rate at least 100 per minute, depth of two inches or more) with minimal interruptions [52]. The effect of CPR quality has been evaluated in several studies [86-88]: In a 2013 systematic review and meta-analysis which included 10 studies (4722 patients total, 4516 of whom experienced out-of-hospital cardiac arrest), persons surviving cardiac arrest were significantly more likely than nonsurvivors to have received deeper chest compressions and have had compression rates between 85 and 100 compressions per minute (compared with shallower and slower compression rates) [86]. https://www.uptodate.com/contents/prognosis-and-outcomes-following-sudden-cardiac-arrest-in-adults/print 12/34 7/6/23, 1:42 PM Prognosis and outcomes following sudden cardiac arrest in adults - UpToDate In a study of 3098 patients with out-of-hospital cardiac arrest, ROSC was highest at a rate of 125 compressions per minute [87]. However, higher chest compression rates were not significantly associated with survival to hospital discharge, which is consistent with the finding in the systematic review and meta-analysis above. (See "Adult basic life support (BLS) for health care providers", section on 'Performance of excellent chest compressions'.) End-tidal carbon dioxide levels have an excellent correlation with very low cardiac outputs when measured after at least 10 minutes of CPR and may provide prognostic information, suggesting that the cardiac output maintained during CPR is a determinant of outcome. This concept is discussed in greater detail elsewhere. (See "Carbon dioxide monitoring (capnography)", section on 'Effectiveness of CPR'.) Body temperature An increase in body temperature is associated with unfavorable functional neurologic recovery after successful CPR. The increase in temperature may be neurally-mediated and can exacerbate the degree of neural injury associated with brain ischemia. For the highest temperature within 48 hours, each degree Celsius higher than 37 C increases the risk of an unfavorable neurologic recovery (OR of 2.26 in one report) [89]. On the other hand, the induction of mild to moderate hypothermia (target temperature 32 to 34 C for 24 hours) may be beneficial in patients successfully resuscitated after a cardiac arrest, although studies have shown variable outcomes. This issue is discussed in greater detail elsewhere. (See "Initial assessment and management of the adult post-cardiac arrest patient", section on 'Temperature management'.) Prehospital ACLS The incremental benefit of deploying EMS personnel trained in ACLS interventions (intubation, insertion of intravenous lines, and intravenous medication administration) on survival after cardiac arrest probably depends upon the quality of other prehospital services. In the OPALS study, ACLS interventions were added to an optimized emergency medical services program of rapid defibrillation [57]. No improvement in the rate of survival for out- of-hospital cardiac arrest was observed with addition of an ACLS program. In a retrospective report from Queensland with an emergency services program not optimized for early defibrillation, the presence of ACLS-skilled EMS personnel was associated with improved survival for out-of-hospital cardiac arrest [90]. Effect of older age The risk of SCA increases with age, and older age has been associated with a poorer survival in some, but not all studies of out-of-hospital cardiac arrests [1,91-95]: https://www.uptodate.com/contents/prognosis-and-outcomes-following-sudden-cardiac-arrest-in-adults/print 13/34 7/6/23, 1:42 PM Prognosis and outcomes following sudden cardiac arrest in adults - UpToDate In one study of 5882 patients who experienced an out-of-hospital cardiac arrest, 22 percent were >80 years of age [96]. Compared with patients <80 years of age, octogenarians and nonagenarians had a lower rate of hospital discharge (9.4 and 4.4 versus 19 percent for those <80). The discharge rate was higher in those with VF or pulseless ventricular tachycardia (VT) as the initial rhythm. Very old patients still had a poorer survival (24 and 17 versus 36 percent), but age was a weaker predictor than the initial rhythm. In the Seattle series of over 12,000 EMS-treated patients, every one-year increase in age was associated with a lower likelihood of survival to hospital discharge for all patients (OR 0.97 per year) and for those with witnessed VF (OR 0.98 per year) [1]. In a study of 36,605 patients ages 70 years or older enrolled in a Swedish registry between 1990 and 2013 following SCA, 30-day survival was significantly higher in patients ages 70 to 79 years (6.7 percent) compared with patients ages 80 to 89 years (4.4 percent) and those over 90 years of age (2.4 percent) [95]. Effect of sex The incidence of SCA is greater in males than females [1,97]. The effect of sex on outcome has been examined in multiple cohorts, with the following findings [97-99]: Males are more likely than females to have VF or VT as an initial rhythm. Males are more likely than females to have a witnessed arrest. Males have a higher one-month survival than females following SCA, due to the higher likelihood of VF/VT as their presenting rhythm. However, when considering only patients with VF/VT as the initial rhythm, females have a greater survival with favorable neurologic outcome. Effect of comorbidities The impact of preexisting chronic conditions on the outcome of out- of-hospital SCA was evaluated in a series of 1043 SCA victims in King County, Washington, in the United States [100]. There was a statistically significant reduction in the probability of survival to hospital discharge with increasing numbers of chronic conditions, such as congestive heart failure, prior MI, hypertension, and diabetes (OR 0.84 for each additional chronic condition). The impact of comorbidities was more prominent with longer EMS response intervals. Association of depression and anxiety with long-term outcomes In a study of 2373 patients from South Korea with out-of-hospital cardiac arrest followed for a median of 5.1 years for the outcome of mortality, 16.7 percent were diagnosed with depression or anxiety [101]. Patients with depression or anxiety had a higher rate of long-term mortality versus those without these conditions (35.5 versus 27 percent; adjusted hazard ratio 1.41; 95% CI 1.17-1.70). https://www.uptodate.com/contents/prognosis-and-outcomes-following-sudden-cardiac-arrest-in-adults/print 14/34 7/6/23, 1:42 PM Prognosis and outcomes following sudden cardiac arrest in adults - UpToDate FACTORS AFFECTING IN-HOSPITAL SCA OUTCOME The outcome of patients who experience SCA in the hospital is poor, with reported survival to hospital discharge rates of 6 to 19 percent [102-107]. However, outcomes appear to be improving over time [106,108]. In a cohort of 64,339 patients at 435 hospitals who had in-hospital SCA between 2000 and 2008 and underwent standard resuscitation procedures, 49 percent had return of spontaneous circulation (ROSC), with 15 percent overall survival to hospital discharge [105]. In a cohort of 151,071 adults at 470 United States hospitals who had in-hospital SCA between 2000 and 2014, 62 percent had ROSC, with 19 percent overall survival to hospital discharge [106]. In this study, patients with SCA during "on hours" (Monday through Friday from 7 AM through 11 PM) had significantly greater survival compared with SCA occurring during "off hours" (Monday through Friday from 11:00 PM through 7:00 AM and all day Saturday and Sunday); this difference did not significantly change between 2000 (16 versus 11.9 percent, respectively) and 2014 (25.2 versus 21.9 percent, respectively). Specific factors Several clinical factors have been identified that predict a greater likelihood of survival to hospital discharge [102,105,106,109]: Witnessed arrest. Ventricular tachycardia (VT) or ventricular fibrillation (VF) as initial rhythm. Pulse regained during first 10 minutes of CPR. Arrest during "on hours" (Monday through Friday from 7:00 AM through 11:00 PM). Identification of early warning signs. The presence of a dedicated resuscitation team with diverse team composition, clearly defined roles and communication, and ongoing training [110]. Other factors have been identified that predict a lower likelihood of survival to hospital discharge [109,111]: Longer duration of overall resuscitation efforts. Multiple resuscitation efforts. https://www.uptodate.com/contents/prognosis-and-outcomes-following-sudden-cardiac-arrest-in-adults/print 15/34 7/6/23, 1:42 PM Prognosis and outcomes following sudden cardiac arrest in adults - UpToDate Delays in providing initial defibrillation have been associated with worse outcomes. This was illustrated in a report of 6789 patients with in-hospital SCA due to VT or VF from 369 hospitals participating in the National Registry of Cardiopulmonary Resuscitation [111]. Delayed defibrillation (more than two minutes after SCA) occurred in 30 percent of patients and was associated with a significantly lower probability of surviving to hospital discharge (22.2 versus 39.3 percent). Delayed defibrillation was more common with noncardiac admitting diagnosis, cardiac arrest at a hospital with fewer than 250 beds, an unmonitored hospital unit, and arrest during after-hours periods. A national early warning score (NEWS) was developed in the United Kingdom in 2012 and updated in 2017 in an effort to standardize early detection of patients at risk for in-hospital SCA [112]. The score incorporates seven vital signs (respiratory rate, oxygen saturation, supplemental oxygen, heart rate, systolic blood pressure, temperature, and level of consciousness), with a maximal score of 20 points (0 to 4, 5 to 6, and 7 or more considered low, medium, and high scores, respectively). In a single-center study of all in-hospital SCA in 2014 and 2015, patients had markedly high risk of dying from SCA if they had a medium (odds ratio [OR] 4.4, 95% CI 1.8- 10.8) or high (OR 9.9, 95% CI 2.8-35.3) NEWS score compared with patients with a low NEWS score [113]. Multiple resuscitations involving CPR have also been associated with worse outcomes. Among 166,519 hospitalized patients (from the Nationwide Inpatient Sample, an all-payer United States hospital database) who underwent CPR while hospitalized between 2000 and 2009, 3.4 percent survived the initial CPR and ultimately had multiple rounds of CPR during their hospitalization [109]. Patients who had multiple rounds of CPR had a significantly lower likelihood of survival to discharge (OR 0.41, 95% CI 0.37-0.44), and those who survived multiple rounds of CPR had high hospitalization costs and were more likely to be discharged to hospice care. Survival following in-hospital SCA treated with an automated external defibrillator (AED) has also been evaluated using data derived from the National Registry of Cardiopulmonary Resuscitation [114]. When compared with usual resuscitative care, the use of an AED did not improve survival among patients with a shockable rhythm and was associated with a lower survival to hospital discharge among patients with a nonshockable rhythm. (See "Automated external defibrillators", section on 'In-hospital AED allocation'.) In 2013 the American Heart Association issued consensus recommendations regarding strategies for improving outcomes following in-hospital SCA [115]. While the consensus recommendations focused on many of the same factors as out-of-hospital cardiac arrest (ie, early identification of SCA, provision of high-quality CPR, early defibrillation [when indicated]), the authors commented on a lack of evidence specifically focused on in-hospital SCA, with many https://www.uptodate.com/contents/prognosis-and-outcomes-following-sudden-cardiac-arrest-in-adults/print 16/34 7/6/23, 1:42 PM Prognosis and outcomes following sudden cardiac arrest in adults - UpToDate of the current guideline recommendations based on extrapolations of data from out-of-hospital SCA. Further data specifically focusing on in-hospital SCA are required prior to making any additional recommendations. GO-FAR score to predict neurologically intact survival The ability to predict neurologically favorable survival following in-hospital SCA has not been well-defined, with most estimates based on clinical judgment of the treating clinician(s). However, it seems most likely that no single factor can effectively predict outcomes but rather a combination of factors. Using data obtained from 366 United States hospitals participating in the Get With The Guidelines-Resuscitation registry, 51,240 patients were identified who experienced in-hospital SCA during the period from 2007 to 2009 [116]. The data were used to derive (44.4 percent), test (22.2 percent) and validate (33.4 percent) the GO-FAR score predicting the likelihood of survival with good neurologic function following SCA based on 13 clinical variables. Patients were divided into the following groups based on likelihood of survival to discharge: Very low likelihood of survival (<1 percent chance) Score of 24 or greater Low likelihood of survival (1 to 3 percent chance) Score 14 to 23 Average likelihood of survival (>3 to 15 percent chance) Score -5 to 13 Higher than average likelihood of survival (>15 percent chance) Score -15 to -6 In general, younger patients with normal baseline neurologic function and fewer medical comorbidities had a greater likelihood of survival following in-hospital SCA [117]. A subsequent prospective registry study of 62,131 patients with in-hospital SCA between 2010 and 2016 validated the ability of the GO-FAR score to predict the chance of survival; survival rates were slightly higher, likely related to ongoing improvements in postresuscitation care [118]. The GO- FAR score appears to be an effective aid for patients and/or caregivers to better understand the likely goals and outcomes of care. (See "Communication in the ICU: Holding a meeting with families and caregivers", section on 'Sharing clinical information'.) IMPACT OF ARTERIAL OXYGEN LEVEL Oxygenation goals should be individualized and hyperoxia should be avoided. Arterial hyperoxia early after SCA may have deleterious effects, perhaps due to oxidative injury. The 2008 International Liaison Committee on Resuscitation cited preclinical evidence of harm from hyperoxia and suggested a goal arterial oxygenation of 94 to 96 percent post SCA [119]. A more detailed discussion of oxygenation with mechanical ventilation is presented separately. (See "Overview of initiating invasive mechanical ventilation in adults in the intensive care unit", section on 'Fraction of inspired oxygen'.) https://www.uptodate.com/contents/prognosis-and-outcomes-following-sudden-cardiac-arrest-in-adults/print 17/34 7/6/23, 1:42 PM Prognosis and outcomes following sudden cardiac arrest in adults - UpToDate A study to examine this issue was performed using a multicenter database including 6326 patients with arterial blood gas analysis within 24 hours after ICU arrival following cardiac arrest [120]. The study included patients with in-hospital and out-of-hospital SCA (57 percent were hospital inpatients and 43 percent were from the emergency department). Oxygenation status was categorized according to the first ICU arterial blood gas value, with hyperoxia defined as PaO2 300 mmHg, hypoxia as PaO2 <60 mmHg, and the remaining as normoxia. The majority of patients had hypoxia (63 percent) with similar numbers having hyperoxia (18 percent) and normoxia (19 percent). The hyperoxia group had higher in-hospital mortality compared with the normoxia and the hypoxia groups (63 percent versus 45 percent and 57 percent). In a multivariable model, hyperoxia was an independent risk factor for death (odds ratio [OR] 1.8, 95% CI 1.5-2.2). Hypoxia was also an independent risk factor (OR 1.3, 95% CI 1.1-1.5). Further data are needed to determine the impact of oxygen titration during and after resuscitation. In a subsequent, smaller, prospective cohort study of 280 patients with cardiac arrest, among whom 105 patients (38 percent) were exposed to hyperoxia (defined as PaO2 >300 mmHg) during the first six hours of care after return of spontaneous circulation, death or poor neurologic function at discharge (defined as modified Rankin score >3) was significantly more likely in patients exposed to hyperoxia (77 versus 65 percent) [121]. LONG-TERM OUTCOME The reported long-term survival of resuscitated SCD is variable and may depend upon multiple factors: In patients with out-of-hospital ventricular fibrillation, was early defibrillation achieved? Do the data come from randomized trials, in which many, often sicker, patients are excluded, or from community-based observations? Was the patient treated with early revascularization, antiarrhythmic drugs, or an implantable cardioverter-defibrillator (ICD)? Does the patient have other risk factors, particularly a reduced left ventricular ejection fraction? Do patients with seemingly transient or reversible causes of SCA have a better prognosis? Did the episode of SCA begin as ventricular fibrillation (VF) or ventricular tachycardia (VT)? The potential effect of successful early defibrillation on long-term outcome following out-of- hospital cardiac arrest due to VF was assessed in a population-based study of 200 patients [122]. https://www.uptodate.com/contents/prognosis-and-outcomes-following-sudden-cardiac-arrest-in-adults/print 18/34 7/6/23, 1:42 PM Prognosis and outcomes following sudden cardiac arrest in adults - UpToDate Over 70 percent of these patients survived until hospital admission, and 40 percent of these patients were discharged with mild or absent neurologic impairment. Among these 79 patients, 43 underwent coronary revascularization and 35 received an ICD, 13 of whom had subsequent shocks for VT or VF. The expected five-year survival of the study population (79 percent) was the same as that of age-, sex-, and disease-matched controls who did not have out-of-hospital cardiac arrest, but significantly lower than age- and sex-matched controls in the general population. INFORMATION FOR PATIENTS UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." th th The Basics patient education pieces are written in plain language, at the 5 to 6 grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more th th sophisticated, and more detailed. These articles are written at the 10 to 12 grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon. Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.) Basics topics (see "Patient education: Sudden cardiac arrest (The Basics)") SUMMARY AND RECOMMENDATIONS Prognosis following cardiac arrest Despite advances in the treatment of heart disease, the outcome of patients experiencing sudden cardiac arrest (SCA) remains poor. The reasons for the continued poor outcomes are likely multifactorial (eg, delayed bystander cardiopulmonary resuscitation [CPR], delayed defibrillation, advanced age, decreased proportion presenting with ventricular fibrillation [VF]). (See 'Prognosis following sudden cardiac arrest' above.) Outcome When SCA is due to a ventricular tachyarrhythmia, the outcome of resuscitation is better compared with those with asystole or pulseless electrical activity. (See 'Outcome according to etiology' above.) https://www.uptodate.com/contents/prognosis-and-outcomes-following-sudden-cardiac-arrest-in-adults/print 19/34 7/6/23, 1:42 PM Prognosis and outcomes following sudden cardiac arrest in adults - UpToDate Factors affecting outcome Among the many factors that appear to have an influence on the outcome of SCA, the elapsed time prior to effective resuscitation (ie, establishment of an effective pulse) appears to be the most critical element. There are several ways to decrease the time to the onset of resuscitative efforts: Rapid emergency medical services (EMS) response Optimizing the EMS system within a community to reduce the response interval to eight minutes or less has been proposed as a way to improve the outcomes of SCA. However, due to a variety of factors, EMS response time of eight minutes or less cannot always be achieved. (See 'Time to resuscitation' above.) Bystander CPR The administration of CPR by a layperson bystander (bystander CPR) is an important factor in determining patient outcome after out-of-hospital SCA, as early restoration or improvement in circulation has been shown to result in greater survival and better neurologic function among survivors. Bystander CPR, however, is not always performed, primarily due to the bystander s lack of CPR training and/or concerns about possible transmission of disease while performing rescue breathing. (See 'Bystander CPR' above.) Early defibrillation The standard of care for resuscitation of SCA has been defibrillation as soon as possible when indicated. Shorter defibrillation response intervals correlate with greater survival to hospital discharge. (See 'Timing of defibrillation' above and "Advanced cardiac life support (ACLS) in adults".) Automated external defibrillators The use of automated external defibrillators (AEDs) by early responders is another approach to more rapid resuscitation. In most, but not all studies, AEDs have been found to improve survival after out-of-hospital cardiac arrest. (See "Automated external defibrillators".) Cardiopulmonary resuscitation Several observational studies evaluating compression- only CPR versus standard CPR including rescue breathing reported no significant differences in survival or long-term neurologic function between the two groups, suggesting that compression-only CPR could be safely delivered (as long as the arrest is not a respiratory arrest). Three randomized trials of compression-only CPR versus standard CPR have all shown a trend toward improved outcomes in the compression-only CPR group, and a 2010 meta-analysis of the three randomized trials reported an increased survival to hospital discharge among patients who received compression-only CPR. As such, if a sole bystander is present or multiple bystanders are reluctant to perform mouth- to-mouth ventilation, we encourage the performance of CPR using chest compressions https://www.uptodate.com/contents/prognosis-and-outcomes-following-sudden-cardiac-arrest-in-adults/print 20/34 7/6/23, 1:42 PM Prognosis and outcomes following sudden cardiac arrest in adults - UpToDate only. (See 'Bystander CPR' above and "Adult basic life support (BLS) for health care providers", section on 'Chest compressions'.) Temperature management The induction of mild to moderate hypothermia (target temperature 32 to 34 C for 24 hours) may be beneficial in patients successfully resuscitated after a cardiac arrest. Improved neurologic outcome and reduced mortality has been demonstrated in series of patients with VF arrest in whom spontaneous circulation was restored, even when the patient remains comatose after resuscitation. (See "Initial assessment and management of the adult post-cardiac arrest patient", section on 'Temperature management'.) ACKNOWLEDGMENT The UpToDate editorial staff acknowledges Jie Cheng, MD, who contributed to an earlier version of this topic review. Use of UpToDate is subject to the Terms of Use. REFERENCES 1. Rea TD, Eisenberg MS, Becker LJ, et al. Temporal trends in sudden cardiac arrest: a 25-year emergency medical services perspective. Circulation 2003; 107:2780. 2. Rea TD, Crouthamel M, Eisenberg MS, et al. Temporal patterns in long-term survival after resuscitation from out-of-hospital cardiac arrest. Circulation 2003; 108:1196. 3. Kitamura T, Iwami T, Kawamura T, et al. Nationwide improvements in survival from out-of- hospital cardiac arrest in Japan. Circulation 2012; 126:2834. 4. Chan PS, McNally B, Tang F, et al. Recent trends in survival from out-of-hospital cardiac arrest in the United States. Circulation 2014; 130:1876. 5. Wong MK, Morrison LJ, Qiu F, et al. 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