Sudden cardiac arrest is a major clinical and public health problem, with high mortality rates and the potential for irreversible and profound neurological damage and functional disability. Numerous factors can affect reported incidence and outcomes of out-of-hospital cardiac arrest (OHCA) and in-hospital cardiac arrest (IHCA), primarily because of differences in the underlying sources of data, populations included, types or causes of cardiac arrest, use of different tools to assess specific outcomes, or how cardiac arrest variables are collected and reported.1–3 Survival and neurological recovery following cardiac arrest are affected by multiple interdependent variables that include individual patient characteristics, emergency medical service (EMS) or hospital system characteristics, and circumstantial factors specific to the event.4,5 As incidence, survival, and neurological outcome are influenced by a number of modifiable (e.g. provision of health care) and non-modifiable (e.g. patient characteristics or location of arrest) factors,6,7 the development of national large registries of cardiac arrest is an essential first step for surveillance and quality improvement purposes.8–10

Several countries have developed collective efforts to develop OHCA registries, such as the Pan-Asian Resuscitation Outcomes Study (PAROS) network,11 the European Registry of Cardiac Arrest (EuReCa),12,13 the Cardiac Arrest Registry to Improve Survival (CARES),14,15 the All-Japan Utstein registry,16 the Victoria Ambulance Cardiac Arrest Registry (VACAR),17 the UK National Cardiac Arrest Audit (NCAA) database,18 or the Irish Out of Hospital Cardiac Arrest Register (OHCAR).19 Registries allow for the precise measurement of the mortality and morbidity burden of cardiac arrest, can better guide the selection and implementation of public health interventions, help to determine appropriate allocation of resources, identify at-risk or vulnerable populations, and eliminate potential care disparities through targeted interventions.20 Moreover, it can allow researchers to assess the impact of current and emerging treatments and provide an evidence base for high-quality care and best practices.

In Spain, knowledge about the epidemiology of cardiac arrest is still insufficient,21,22 although results of the first year (2013–1024) of the Out-of-Hospital Spanish Cardiac Arrest Registry (OHSCAR) revealed that OHCA affects a relatively young population, more than a half at home, with bystander of basic life support being performed hardly in one out of three cases.23 In the framework of the National Plan for Cardiopulmonary Resuscitation (PNRCP), a national registry of ICU patients recovering from OHCA or IHCA was developed with the support of the Spanish Society of Intensive Care Medicine and Coronary Units (SEMICYUC).24 The main objectives of this study were identify predictors of mortality and neurological function adult patients recovering from cardiac arrest admitted to Spanish ICUs.

The present study present relevant clinical data of a representative homogeneous sample of adult patients recovering from cardiac arrest and admitted to Spanish ICUs28 over a 17-month period and followed for 12 months after the index episode. We cannot report incidence data since the total number of patients suffering from cardiac arrest attended during the study period is unknown. However, the international, prospective, multicenter EuReCa ONE study of patients who suffered an OHCA during October 2014 attended and/or treated by an EMS from 248 regions in 27 countries, covering an estimated population of 174 million, provided disaggregated data by country.12 For Spain, with a total population of 47,270 inhabitants covering all 17 autonomous communities, an incidence of cardiac arrest of 28 cases per 100,000 inhabitants per year, and an incidence of 19 cases of CPR per 100,000 cases per year was reported.12 Using these data and analyses, different countries, regions, systems, and concepts can benchmark them-selves and may learn from each other to further improve survival.

The templates Utstein-style contribute to improved public health internationally by providing a structured framework with which to compare medical services systems. Representatives of the International Liaison Committee on Resuscitation developed updated Utstein guidelines during 2012 through 2014, with recommendations for reporting OHCA.26 Data elements were grouped by system factors, dispatch/recognition, patient variables, resuscitation/post-resuscitation processes, and outcomes. This template facilitates reporting of the rhythms treated as an efficacy measure of medical services. The update of the IHCA templates is currently pending.

Epidemiological data in our study included a predominance of males, mean age in the sixth decade, bystanders providing resuscitation measures in 48.6% of cases, quite similar rates of OHAC and IHCA, cardiac cause of arrest in 57.3% of cases, shockable rhythms in 47.2%, and ROSC <20min in 62.2%. Data of other studies carried out in Spain have shown similar results.23,29–31 In 8997 patients with OHCA attended by an emergency team of the Spanish EMS over 1-year period (2013–2014),23 72% were men with a mean age of 61 years, initial rhythm was shockable in 22.1% patients, and basic life support before emergency team arrival was provided by bystander in 30% of patients.

The primary objective of the study was to assess survival in patients admitted to the ICU after recovery from cardiac arrest. Of the 595 patients included in the study, 304 (51.1%) were alive at the time of ICU discharge. Sixty-one patients died during hospitalization, with an overall survival rate of 40.8%. Predictors of ICU and in-hospital mortality included age, non-cardiac cause of arrest, ROSC >20min, and CPR time, as well as the presence of shockable rhythms and PCI as protective factors. Cardiac arrest survival rates and the likelihood of good neurologic outcomes and functional status vary substantially according to disparities of the affected patient populations and related comorbidities, the quality of local chain, proximity to trained providers and appropriate treatments, and the number of transitions that must occur between various providers, such as EMS and hospital staff.32 In a recent large, prospective population-based registry conducted over 2 years in Paris, France, the survival rates were 7.3% (279/3816) among patients in which CRP was attempted and 21% (279/1335) among those who were admitted alive to the hospital.33 In the nationwide Danish Cardiac Arrest Registry of a study population of 19,468 patients, the 30-day survival improved from 3.5% in 2001 to 10.8% in 2010, which in turn was significantly associated with a concomitant increase in bystander CPR.34 Moreover, in an analysis of the Get with the Guidelines–Resuscitation Registry of patients with IHCA in the U.S., risk-adjusted rates of survival to discharge in the overall cohort of 84,625 hospitalized patients increased from 13.7% in 2000 to 22.4% in 2009.35 A prospective analysis of the UK National Cardiac Arrest Audit (NCAA) database with data related to 22,628 patients showed an overall unadjusted survival to hospital discharge of 18.4%.36 An analysis of trends in patient characteristics and outcome following admission to UK critical care units following CPR for the period 2004–2014 showed a reduction in mortality following ICU admission (OR 0.96 per year).37 Cariou et al.38 have reported ten priorities for strengthening the local chain of survival in OHCA, including high bystander CPR rate and early defibrillation programs in the community; good quality advanced life support; monitoring the quality of CPR (end-tidal carbon dioxide or near-infrared spectroscopy); developing advanced therapies in refractory cardiac arrest (mechanical chest compression devices, extracorporeal life support); improving post-resuscitation care (hypothermia, PCI); prognostication; rehabilitation; development of high-quality cardiac arrest registries; and to promote and develop high-quality research.

In relation to neurological outcome, shockable rhythm, ROSC <20min, and cardiac cause of arrest were associated with favorable neurological function. In a systematic review of the European Resuscitation Council and the European Society of Intensive Care Medicine,39 bilateral absence of either pupillary and corneal reflexes or N20 wave of short-latency somatosensory evoked potentials were identified as the most robust predictors of poor outcome in adult comatose survivors of cardiac arrest.

Sandroni et al.40 reported a comprehensive review on the prediction of neurological outcome after cardiac arrest and recommended prognostication tests (clinical examination, electrophysiology, biomarkers and neuroimaging) in patients who are comatose at 72h or more after ROSC. Among prognostic tests, ocular reflexes and somatosensory evoked potentials are the most robust. This multimodal approach combining multiple prognostication tests is recommended so that the risk of falsely pessimistic prediction is minimized.

In a systematic review and meta-analysis of 20 studies with 1845 patients, bilateral absence of pupillary reflexes more than 24h after ROSC, bilateral absence of corneal reflexes more than 24h, and bilateral absence of somatosensory-evoked potentials between days 1 and 7 accurately predicted poor neurological outcome.41 Martinell et al.42 presented a score with 10 variables for early identification of patients at high risk of poor prognosis after OHCA of presumed cardiac origin. This study is a post hoc analysis of a cohort of the Target Temperature Management trial applicable only to patients with OHCA of cardiac cause. Predictors of poor outcome were older age, non-defibrillable rhythm and duration of ROSC were similar to that found in our study. Other predictors such as Glasgow Coma score, partial pressure of CO2 in arterial blood value <4.5kPa at hospital admission, and lower pH would have been only applicable to patients with hypothermia in our study (n=197), so it is not possible to make an inference to the total 595 patients included in the study. Other variables such as the administration of adrenaline or the absence of bilateral pupillary of corneal reflexes were nor collected in our database, the design of which was previous to the statement of the European Resuscitation Council of the European Society of Intensive Care Medicine.39 A recent review by Narayan et al.1 describes new challenges to address the sudden cardiac arrest epidemics in the framework of responding, understanding, predicting and preventing. The response could be improved by technology assisted by community response systems (automated external defibrillator). Efforts to understand and predict cardiac arrest can be improved by refining the taxonomy along phenotypic and pathophysiological “risk axes” and prevention must integrate these concepts.

There is no single agreed physical disability measure. The Barthel index is proposed as the standard index for clinical and research purposes. There are few studies reporting long-term follow-up up to 12 months and most have been carried out up to 6 months after the event. Interestingly, the neurological sequelae data measured with the Barthel index after 12 months of the event, with a totally independent rate of 22%, are clinically relevant and have not been previously reported.

At present there is still controversy about the role of hypothermia as a post-resuscitation measure for survival and neurological outcome, and the term temperature control is preferred, 36°C as an objective, although it is still a subject of debate. At the time we designed the study, it was recommended by the European Resuscitation Council and, it seemed appropriate to include it as a study variable in those hospitals in which this technique was available. Therapeutic hypothermia was not selected as an independent predictor of survival in the multivariate analysis probably because other variables, such as age, shockable rhythm, non-cardiac cause of arrest, and duration of CPR were strongly associated with hypothermia. In a systematic review and meta-analysis of 11 studies, the use of therapeutic hypothermia after OHCA decreased the mortality and improved the odds of good neurological outcome, even when including patients with non-shockable rhythms, more lenient downtimes, unwitnessed arrest and/or persistent shock.43 Another systematic review showed a beneficial effect of hypothermia in shockable rhythms only.44 However, in the IHCA setting, use of therapeutic hypothermia compared with usual care was associated with a lower likelihood of survival to hospital discharge and a lower likelihood of favorable neurological survival.45 On the other hand, the benefit of targeted temperature management (TTM) with therapeutic hypothermia has been assessed in a systematic review and meta-analysis with pooled data of five randomized controlled trials with 1389 patients, and no differences in mortality or neurological outcomes were found.46 The authors concluded that employing therapeutic hypothermia as a standard of care strategy of post-arrest care in survivors may need to be reevaluated.

The present study is observational in nature and, as such, is subject to limitations including selection bias as patients with cardiac arrest are attended on site and those not recovering do not reach the hospital, and information bias, particularly regarding difficulties of exact recording of derived times and intervals. The potential effect of confounding variables was addressed by the use of logistic regression analysis. Neurological outcome at follow-up especially at 12 months is limited by the number of losses to follow-up with findings at risk of attrition bias. Also, data on decisions about limitation of life support were not recorded, neither the number of patients who were organ donors and, in this case, if they were in asystole.

In summary, we here report clinically relevant data of the first national registry of patients recovering from cardiac arrest admitted to Spanish ICUs. This information is clinically pertinent and useful since contributes to a better knowledge of the epidemiology, post-resuscitation management, and neurological outcome of patients having cardiac arrest. Salient findings include a similar rate of OHCA and IHCA and a percentage of bystanders lower than 50%, with age, non-cardiac cause of arrest, ROSC >20min, and total CPR as significant predictors of ICU mortality. The most favorable prognosis regarding neurological function was obtained in the presence of shockable rhythm, ROSC <20min, and cardiac cause of the arrest. Data of the neurological sequela measured with the Barthel index after 12 months of the event, with a fully independent rate of 22% is clinically relevant and has not been previously reported.

None declared.