Resuscitation 85 (2014) 671–675
Contents lists available at ScienceDirect
Resuscitation journal homepage: www.elsevier.com/locate/resuscitation
Clinical Paper
Life years saved, standardised mortality rates and causes of death after hospital discharge in out-of-hospital cardiac arrest survivors夽 T. Lindner a,∗ , C. Vossius b,c , W.T. Mathiesen a , E. Søreide a a b c
Department of Anaesthesiology and Intensive Care, Stavanger University Hospital, Norway Stavanger Teaching Nursing Home, Stavanger, Norway Centre for Age-related Medicine, Stavanger University Hospital, Norway
a r t i c l e
i n f o
Article history: Received 18 October 2013 Received in revised form 20 December 2013 Accepted 1 January 2014 Keywords: Out-of-hospital cardiac arrest Resuscitation Long term survivors Standardised mortality rates Causes of death after hospital discharge EMS
a b s t r a c t Aim of the study: Out-of-hospital cardiac arrest (OHCA) accounts for many unexpected deaths in Europe and the survival rates in different regions vary considerably. We have previously reported excellent survival to discharge rates in the Stavanger region. We now describe the long-term outcome of OHCA victims in our region. Methods: In this retrospective observational study, we followed all OHCA hospital discharge survivors between 01.07.2002 and 30.06.2011 (n = 213) for a minimum of 1 year and up to 10 years. Based on the national death statistics stratified for gender and age, we could calculate the potential life years saved, standardised mortality rates (SMR) and delineate the causes of death after hospital discharge. Results: Of the 213 patients who were discharged from the hospital, 91% had a cardiac origin of their OHCA. The mean potential life years saved per patient was 22.8 years. The observed five-year survival rate was 76%. The overall SMR in our study cohort was 2.3 when compared to the age- and gendermatched population. Cardiac disease was a prominent cause of late deaths, with the specific SMR for cardiac disease-related deaths being as high as 42 in males and 140 in females. Conclusion: Resuscitation of OHCA victims lead to a significant long-term benefit with respect to life years saved. Cardiac disease was the main cause of death after hospital discharge. More studies are needed to identify the potential of therapeutic interventions and rehabilitation efforts that may further enhance the long-term outcomes in OHCA hospital discharge survivors. © 2014 Elsevier Ireland Ltd. All rights reserved.
1. Introduction European Emergency Medical Services (EMS) carries out resuscitation in approximately 400 000 out-of-hospital cardiac arrest (OHCA) victims every year.1 Despite all resuscitation efforts, the majority of victims do not survive to be discharged from hospital.1,2 Furthermore, unacceptably large and partly unexplained variations in community and system-based short-term survival exist.1,3 To standardise outcome comparisons between different systems, the revised Utstein template in 2004 recommended survival to hospital discharge as the core outcome measure.4 Nonetheless, some studies have also evaluated the long-term benefits of OHCA treatment by looking at the patients’ 5- to 10-year survival rates.5,6 An earlier Norwegian study reported long-term survival with an
observation period spanning from 1971 to 2002.7 However, all these studies are from the era before aggressive and comprehensive post resuscitation care. Therefore, a new study of the potential long-term survival benefits of resuscitating OHCA victims could be of interest. Our region has repeatedly reported very good short-term outcomes in OHCA victims.8,9 The primary aim of this study was to describe the long-term outcome of OHCA victims that survived to discharge from hospital in our region. By collecting the date and cause of death during the observation period, we could estimate life-years saved by the resuscitation efforts and compare actual survival to that of an age- and gender-matched population. This allowed for the calculation of overall mortality risk and more specifically, the risk of cardiac-related death. 2. Methods
夽 A Spanish translated version of the abstract of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2014.01.002. ∗ Corresponding author at: Department of Anaesthesiology and Intensive Care, Stavanger University Hospital, Box 8100, N-4068 Stavanger, Norway. E-mail addresses: [email protected], [email protected] (T. Lindner). 0300-9572/$ – see front matter © 2014 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.resuscitation.2014.01.002
This is a retrospective observational study from the Stavanger University Hospital (SUH), which is the only receiving hospital for OHCA victims within the catchment area of southern Rogaland County, comprising approximately 330 thousand inhabitants. The
672
T. Lindner et al. / Resuscitation 85 (2014) 671–675
Five persons with residency outside of Norway were also excluded because no information about their health and survival status after discharge from hospital was available. 2.2. Potential life years saved We calculated the potential life years saved based on the assumption that our cohort of survivors discharged after OHCA had the same life expectancy as the rest of the Norwegian population, as given by Statistics Norway in the table “Expected remaining lifetime”.13 This table gives the number of years a person is expected to still live, given their gender and present age. The life expectancy table is updated each year based on the death statistics of the Norwegian population. 2.3. Standardised mortality rates (SMR)
Fig. 1. Definition of the study cohort in the time from July 01, 2002 to June 30, 2011.
organisation of the EMS and in-hospital treatment has previously been described in detail.9–11 In short, a single alarm and dispatch centre is responsible for all call-outs of ambulance units, including one that is manned by an emergency physician, and which all belongs to the same ambulance service run by the SUH itself. The alarm and dispatch centre also advises bystanders in cardiopulmonary resuscitation (CPR), including mouth-to-mouth ventilations. The Norwegian advanced life support (ALS) algorithm from 2005 differs slightly from the ERC guidelines.12 TH was introduced as the standard treatment for OHCA victims in 2002 and PCI on a 24/7 basis in 2004.10,11 Our OHCA registry was established in 1996 and all data is registered in accordance with the Utstein template and its updates.4 2.1. Data collection We included all adult (>18 years) OHCA victims who survived to discharge from the hospital between 01.07.2002 and 30.06.2011. Patients with a traumatic cause of OHCA where excluded, while the remaining patients were classified as cardiac and non-cardiac origin of the OHCA, according to the Utstein definition (Fig. 1). Of the 1367 resuscitation attempts, 403 (30%) involved OHCA of non-cardiac origin. The patients were followed until June 30, 2012, which corresponds to a minimum of one year and up to ten years. In addition to demographic and survival data, we collected the following information from the OHCA registry: assumed origin of CA (cardiac or non-cardiac), first registered cardiac-rhythm (shockable or non-shockable), whether the patient was treated with TH and underwent coronary angiography or PCI, where the patient was discharged to and cerebral performance category (CPC)4 at discharge from hospital. The dates of death of the discharged survivors were collected from the Norwegian national registry. This central registry is administered by the Norwegian tax authorities and contains information about every citizen’s name, address, date of birth and eventual date of death. The electronic journal system at SUH is directly linked to the national registry, which is updated once a week. It was accessed July 9, 2012, to verify survival and eventual date of death. Death certificates stating cause of death of the discharged survivors were supplied by Statistics Norway.
The standardised mortality rate (SMR) describes the relative risk of death within a study cohort compared to the general population. The mortality rates for the general population in Norway are provided by Statistics Norway as the deaths per 100,000 Norwegians, and are stratified by gender, age groups with 5-year steps, and for each individual year between 2002 and 2011.14 As the study participants grew older during the course of the study period, the age groups were adjusted each year. We calculated the SMR for each year after the OHCA event and for the whole observation period based on the observed mortality in the study cohort, the time under risk of the study population and the mortality rates as given by Statistics Norway. The SMRs for death of cardiac origin were based on the mortality rates given for the periods 01.01.2002–31.12.2006 and 01.01.2007–31.12.2011, including the diagnoses I20–25, I30–33, I39–52, according to the International Classification of Diseases, version 10 (ICD10). These mortality rates were stratified by gender, but not by age.15 We assumed that these mortality rates were the same for the study period. 2.4. Statistics The software programme, PASW 18.0 (SPSS Inc,; Chicago, USA), was used for statistical analysis. Independent-samples t-test was used to compare the means of continuous parametric variables. The relationship between categorical variables was explored by Chi-square tests when all expected cell frequencies were equal or greater than five. Otherwise, Fischer’s Exact Probability Test was applied. We used the Kaplan Meier survival analysis to estimate the survival rates at one and five years. The log-rank test was used to compare the survival rates with respect to cardiac versus noncardiac origin of OHCA and male versus female gender. Bootstrap analysis with 1000 repetitions was applied to evaluate the confidence intervals (CI) of mortality rates. Two-sided p-values of less than 0.05 were considered statistically significant. The results are stated with their standard deviation (SD) or 95% CI, where applicable. The study was approved by the regional ethics committee. 3. Results 3.1. Study population The 1367 resuscitation attempts (Fig. 1) resulted in 218 hospital discharge survivors (16%), of which 213 (173 males and 40 females) could be followed up and constituted the study cohort (Table 1 and Fig. 1). The observation period covered a total of 920 patient years, with a mean of 4.3 years per person. During the observation period, 54 (25%) individuals died, and the mean time to death was 2.8 years (SD 2.5). The mean age at death was 73.8 years (SD 14.0).
T. Lindner et al. / Resuscitation 85 (2014) 671–675
673
Table 1 Characteristics of the study population cohort. All patients
Alive during follow up
Death during follow up
p value
Number (%) Age at time of OHCA, mean (SD)
213 (100) 61 (15)
159 (75) 58 (14)
54 (25) 71 (13)
Contents lists available at ScienceDirect
Resuscitation journal homepage: www.elsevier.com/locate/resuscitation
Clinical Paper
Life years saved, standardised mortality rates and causes of death after hospital discharge in out-of-hospital cardiac arrest survivors夽 T. Lindner a,∗ , C. Vossius b,c , W.T. Mathiesen a , E. Søreide a a b c
Department of Anaesthesiology and Intensive Care, Stavanger University Hospital, Norway Stavanger Teaching Nursing Home, Stavanger, Norway Centre for Age-related Medicine, Stavanger University Hospital, Norway
a r t i c l e
i n f o
Article history: Received 18 October 2013 Received in revised form 20 December 2013 Accepted 1 January 2014 Keywords: Out-of-hospital cardiac arrest Resuscitation Long term survivors Standardised mortality rates Causes of death after hospital discharge EMS
a b s t r a c t Aim of the study: Out-of-hospital cardiac arrest (OHCA) accounts for many unexpected deaths in Europe and the survival rates in different regions vary considerably. We have previously reported excellent survival to discharge rates in the Stavanger region. We now describe the long-term outcome of OHCA victims in our region. Methods: In this retrospective observational study, we followed all OHCA hospital discharge survivors between 01.07.2002 and 30.06.2011 (n = 213) for a minimum of 1 year and up to 10 years. Based on the national death statistics stratified for gender and age, we could calculate the potential life years saved, standardised mortality rates (SMR) and delineate the causes of death after hospital discharge. Results: Of the 213 patients who were discharged from the hospital, 91% had a cardiac origin of their OHCA. The mean potential life years saved per patient was 22.8 years. The observed five-year survival rate was 76%. The overall SMR in our study cohort was 2.3 when compared to the age- and gendermatched population. Cardiac disease was a prominent cause of late deaths, with the specific SMR for cardiac disease-related deaths being as high as 42 in males and 140 in females. Conclusion: Resuscitation of OHCA victims lead to a significant long-term benefit with respect to life years saved. Cardiac disease was the main cause of death after hospital discharge. More studies are needed to identify the potential of therapeutic interventions and rehabilitation efforts that may further enhance the long-term outcomes in OHCA hospital discharge survivors. © 2014 Elsevier Ireland Ltd. All rights reserved.
1. Introduction European Emergency Medical Services (EMS) carries out resuscitation in approximately 400 000 out-of-hospital cardiac arrest (OHCA) victims every year.1 Despite all resuscitation efforts, the majority of victims do not survive to be discharged from hospital.1,2 Furthermore, unacceptably large and partly unexplained variations in community and system-based short-term survival exist.1,3 To standardise outcome comparisons between different systems, the revised Utstein template in 2004 recommended survival to hospital discharge as the core outcome measure.4 Nonetheless, some studies have also evaluated the long-term benefits of OHCA treatment by looking at the patients’ 5- to 10-year survival rates.5,6 An earlier Norwegian study reported long-term survival with an
observation period spanning from 1971 to 2002.7 However, all these studies are from the era before aggressive and comprehensive post resuscitation care. Therefore, a new study of the potential long-term survival benefits of resuscitating OHCA victims could be of interest. Our region has repeatedly reported very good short-term outcomes in OHCA victims.8,9 The primary aim of this study was to describe the long-term outcome of OHCA victims that survived to discharge from hospital in our region. By collecting the date and cause of death during the observation period, we could estimate life-years saved by the resuscitation efforts and compare actual survival to that of an age- and gender-matched population. This allowed for the calculation of overall mortality risk and more specifically, the risk of cardiac-related death. 2. Methods
夽 A Spanish translated version of the abstract of this article appears as Appendix in the final online version at http://dx.doi.org/10.1016/j.resuscitation.2014.01.002. ∗ Corresponding author at: Department of Anaesthesiology and Intensive Care, Stavanger University Hospital, Box 8100, N-4068 Stavanger, Norway. E-mail addresses: [email protected], [email protected] (T. Lindner). 0300-9572/$ – see front matter © 2014 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.resuscitation.2014.01.002
This is a retrospective observational study from the Stavanger University Hospital (SUH), which is the only receiving hospital for OHCA victims within the catchment area of southern Rogaland County, comprising approximately 330 thousand inhabitants. The
672
T. Lindner et al. / Resuscitation 85 (2014) 671–675
Five persons with residency outside of Norway were also excluded because no information about their health and survival status after discharge from hospital was available. 2.2. Potential life years saved We calculated the potential life years saved based on the assumption that our cohort of survivors discharged after OHCA had the same life expectancy as the rest of the Norwegian population, as given by Statistics Norway in the table “Expected remaining lifetime”.13 This table gives the number of years a person is expected to still live, given their gender and present age. The life expectancy table is updated each year based on the death statistics of the Norwegian population. 2.3. Standardised mortality rates (SMR)
Fig. 1. Definition of the study cohort in the time from July 01, 2002 to June 30, 2011.
organisation of the EMS and in-hospital treatment has previously been described in detail.9–11 In short, a single alarm and dispatch centre is responsible for all call-outs of ambulance units, including one that is manned by an emergency physician, and which all belongs to the same ambulance service run by the SUH itself. The alarm and dispatch centre also advises bystanders in cardiopulmonary resuscitation (CPR), including mouth-to-mouth ventilations. The Norwegian advanced life support (ALS) algorithm from 2005 differs slightly from the ERC guidelines.12 TH was introduced as the standard treatment for OHCA victims in 2002 and PCI on a 24/7 basis in 2004.10,11 Our OHCA registry was established in 1996 and all data is registered in accordance with the Utstein template and its updates.4 2.1. Data collection We included all adult (>18 years) OHCA victims who survived to discharge from the hospital between 01.07.2002 and 30.06.2011. Patients with a traumatic cause of OHCA where excluded, while the remaining patients were classified as cardiac and non-cardiac origin of the OHCA, according to the Utstein definition (Fig. 1). Of the 1367 resuscitation attempts, 403 (30%) involved OHCA of non-cardiac origin. The patients were followed until June 30, 2012, which corresponds to a minimum of one year and up to ten years. In addition to demographic and survival data, we collected the following information from the OHCA registry: assumed origin of CA (cardiac or non-cardiac), first registered cardiac-rhythm (shockable or non-shockable), whether the patient was treated with TH and underwent coronary angiography or PCI, where the patient was discharged to and cerebral performance category (CPC)4 at discharge from hospital. The dates of death of the discharged survivors were collected from the Norwegian national registry. This central registry is administered by the Norwegian tax authorities and contains information about every citizen’s name, address, date of birth and eventual date of death. The electronic journal system at SUH is directly linked to the national registry, which is updated once a week. It was accessed July 9, 2012, to verify survival and eventual date of death. Death certificates stating cause of death of the discharged survivors were supplied by Statistics Norway.
The standardised mortality rate (SMR) describes the relative risk of death within a study cohort compared to the general population. The mortality rates for the general population in Norway are provided by Statistics Norway as the deaths per 100,000 Norwegians, and are stratified by gender, age groups with 5-year steps, and for each individual year between 2002 and 2011.14 As the study participants grew older during the course of the study period, the age groups were adjusted each year. We calculated the SMR for each year after the OHCA event and for the whole observation period based on the observed mortality in the study cohort, the time under risk of the study population and the mortality rates as given by Statistics Norway. The SMRs for death of cardiac origin were based on the mortality rates given for the periods 01.01.2002–31.12.2006 and 01.01.2007–31.12.2011, including the diagnoses I20–25, I30–33, I39–52, according to the International Classification of Diseases, version 10 (ICD10). These mortality rates were stratified by gender, but not by age.15 We assumed that these mortality rates were the same for the study period. 2.4. Statistics The software programme, PASW 18.0 (SPSS Inc,; Chicago, USA), was used for statistical analysis. Independent-samples t-test was used to compare the means of continuous parametric variables. The relationship between categorical variables was explored by Chi-square tests when all expected cell frequencies were equal or greater than five. Otherwise, Fischer’s Exact Probability Test was applied. We used the Kaplan Meier survival analysis to estimate the survival rates at one and five years. The log-rank test was used to compare the survival rates with respect to cardiac versus noncardiac origin of OHCA and male versus female gender. Bootstrap analysis with 1000 repetitions was applied to evaluate the confidence intervals (CI) of mortality rates. Two-sided p-values of less than 0.05 were considered statistically significant. The results are stated with their standard deviation (SD) or 95% CI, where applicable. The study was approved by the regional ethics committee. 3. Results 3.1. Study population The 1367 resuscitation attempts (Fig. 1) resulted in 218 hospital discharge survivors (16%), of which 213 (173 males and 40 females) could be followed up and constituted the study cohort (Table 1 and Fig. 1). The observation period covered a total of 920 patient years, with a mean of 4.3 years per person. During the observation period, 54 (25%) individuals died, and the mean time to death was 2.8 years (SD 2.5). The mean age at death was 73.8 years (SD 14.0).
T. Lindner et al. / Resuscitation 85 (2014) 671–675
673
Table 1 Characteristics of the study population cohort. All patients
Alive during follow up
Death during follow up
p value
Number (%) Age at time of OHCA, mean (SD)
213 (100) 61 (15)
159 (75) 58 (14)
54 (25) 71 (13)
