Article, Cardiology

Characteristics and outcome among 14,933 adult cases of in-hospital cardiac arrest: A nationwide study with the emphasis on gender and age

a b s t r a c t

Aim: To investigate characteristics and outcome among patients suffering in-hospital cardiac arrest (IHCA) with the emphasis on gender and age.

Methods: Using the Swedish Register of Cardiopulmonary Resuscitation, we analyzed associations between gen- der, age and co-morbidities, etiology, management, 30-day survival and cerebral function among survivors in 14,933 cases of IHCA. Age was divided into three ordered categories: young (18-49 years), middle-aged (50- 64 years) and older (65 years and above). Comparisons between men and women were age adjusted.

Results: The mean age was 72.7 years and women were significantly older than men. Renal dysfunction was the most prevalent co-morbidity. Myocardial infarction/ischemia was the most common condition preceding IHCA, with men having 27% higher odds of having MI as the Underlying etiology. A shockable rhythm was found in 31.8% of patients, with men having 52% higher odds of being found in VT/VF. After adjusting for various con- founders, it was found that men had a 10% lower chance than women of surviving to 30 days. older individuals were managed less aggressively than younger patients. Increasing age was associated with lower 30-day survival but not with poorer cerebral function among survivors.

Conclusion: When adjusting for various confounders, it was found that men had a 10% lower chance than women of surviving to 30 days after in-hospital cardiac arrest. Older individuals were managed less aggressively than younger patients, despite a lower chance of survival. Higher age was, however, not associated with poorer cere- bral function among survivors.

(C) 2017

  1. Introduction

In the United States, approximately 200,000 people are treated for in-hospital cardiac arrest (IHCA) every year. In overall terms, 25% of these patients survive to discharge from hospital [1], but survival rates vary from 18% to 36% across hospitals [2,3]. The UK analysis of the Na- tional Cardiac Arrest Audit database (2011 to 2013) revealed that the in- cidence of IHCA was 1.6 occurrences per 1000 hospital admissions [2]. Previous studies have demonstrated that age, gender, initial rhythm,

* Corresponding author at: Grona straket 4, 43146 Gothenburg, Sweden.

E-mail address: [email protected] (N. Al-Dury).

witnessed cardiac arrest , time of day, etiology, time to treatment and duration of CA are independent predictors of survival after IHCA [3-9].

Approximately 60% of patients suffering an IHCA are men [10] and the reason why IHCA is more common in men is not clear. The median age in patients who suffer from IHCA for both genders has been report- ed to be about 70 years, with an inverse relationship between age and survival [3,6]. Previous studies indicate that survival to discharge from hospital after out-of-hospital cardiac arrest (OHCA) varies between 3 and 20% and the highest survival rates have been reported at the age of 10-35 years. Survival then decreases with increasing age [11-13].A recent study found that the risk-adjusted rate of one-year survival

http://dx.doi.org/10.1016/j.ajem.2017.06.012

0735-6757/(C) 2017

among patients who were discharged alive from hospital after IHCA was lower in older patients [14].

The initial rhythm has been reported to be the strongest factor af- fecting the prognosis among patients who suffer from IHCA [15,16]. Sur- vival to discharge from hospital has been reported to be about 50% when the initial rhythm was shockable (hemodynamically significant Ventricular tachycardia or ventricular fibrillation (VF)) and about 10% when the initial rhythm was not shockable (pulseless electrical ac- tivity (PEA) or asystole) [2]. It has been reported that men present with VF/VT as the initial rhythm more frequently than women, who are more likely to have PEA as the initial rhythm [3]. Among patients found in PEA, men have been reported to receive more defibrillations and also to be intubated more frequently [3,17]. However, no significant gender differences have been found regarding the time to defibrillation [3]. Data on both OHCA and IHCA conflict as to whether Female gender is as- sociated with better survival after cardiac arrest [3-5,18-21].

With regard to co-existing conditions, women have been reported to have a lower prevalence of a history of myocardial infarction (MI), angi- na pectoris and renal disease but a higher prevalence of rheumatic dis- ease [3]. Approximately 80% of IHCA survivors have been reported to be discharged with a Cerebral Performance Category of 1 or 2 (no to mild neurological disability), with no differences between men and women [3,14,22].

To our knowledge, there are no large nationwide studies, with sim- ilar high coverage, compared with the Swedish Register of Cardiopul- monary Resuscitation, on which our study is based. Sixty-nine hospitals currently report to the register, which indicates coverage of about 95% of the emergency hospitals in Sweden, including 98% of all Hospital beds, since the four hospitals which do not report to the register are small hospitals, making this study the most comprehensive of its kind to date.

The aim of this study is to describe IHCA from an age and gender per- spective, in a nationwide registry covering the majority of hospital beds in a single country. The high coverage facilitates generalizability of the results and limits the effects of any inter-hospital variation. The primary aim was to analyze gender differences in adjusted 30-day survival.

  1. Methods
    1. The Swedish Register of Cardiopulmonary Resuscitation

This register is a national quality register of OHCA and IHCA. It serves as a tool for the prospective quality control of resuscitation practices in Sweden. It is funded by the Swedish Association of Local Authorities and Regions, which encourages all pre-hospital centers and hospitals to par- ticipate in reporting. The register employs standardized Utstein-style definitions for all variables and outcomes. Reporting to the register in- volves two steps; the first includes reporting baseline information, e.g. the location of the arrest, treatments provided, delay to treatment and survival after the resuscitation attempt. The second step involves fol- low-up data, e.g. probable etiology of the cardiac arrest and 30-day sur- vival data. In addition, CPC scoring is performed at discharge from hospital among survivors [23,24].

Study population

Data on IHCA have been collected since 2007 and cover all patients who suffered a cardiac arrest and underwent cardiopulmonary resusci- tation within the hospital perimeter. During the first year, only ten hos- pitals participated, but since then the number of participating hospitals has successively increased. The register contains approximately 15,000 cases of IHCA as of 31 December 2014. Patients younger than 18 years of age were excluded from our study. We collected information on age, gender, co-morbidities (heart failure, acute myocardial infarction, stroke and renal dysfunction), on-going conditions (acute myocardial infarction and stroke), likely etiology, time and place of arrest,

treatment delays, survival to discharge and at 30 days and CPC score among survivors at discharge. For the purpose of this paper, patients were analyzed according to gender and age. Patients were thus divided into three age groups: young (18-49 years), middle-aged (50-64 years) and older (65 years and above).

Definition of variables

The term “in-hospital” refers to all cardiac arrest events within the hospital perimeter, without the need for Ambulance transport. Only events in which cardiopulmonary resuscitation (CPR) had been attempted were registered. This means that, when a cardiac arrest oc- curs, the hospital staff dial a specific number and a CPR team is immedi- ately alerted (so-called rescue team activation). Only the first cardiac arrest episode/admission/patient was included as a case in this study. Previous medical history was obtained from the patients’ notes, based on previously specified definitions. Heart failure refers to all forms of heart failure with the exception of pulmonary edema within one hour before the arrest. A previous history of MI refers to MI preceding the ar- rest by 72 h or more. On-going MI refers to MI within 72 h before the ar- rest. Respiratory insufficiency refers to all types of respiratory insufficiency with or without the need for a respirator. Previous stroke refers to any hemorrhagic or ischemic stroke before the current hospi- talization period. On-going stroke refers to any stroke during the cur- rent hospitalization period. Renal dysfunction was defined as a glomerular filtration rate (GFR) of b 60 ml/min based on the highest level of serum creatinine recorded after hospital admission. The esti- mated global filtration rate using plasma creatinine adjusted for age and gender was calculated using the revised Lund-Malmo formula [25]. Weekday is defined as a working day, Monday to Friday (excluding public holidays). Daytime is defined as 8 am to 8 pm. The CPC score eval- uates the neurological status of the patient on a five-point scale, with one indicating mild or no neurological disability, two indicating moder- ate disability, three indicating severe disability, four indicating coma or vegetative state and five indicating brain death [26].

Validation of the reported data

Validation has taken place at 34 hospitals comprising 1338 patients. Based on this validation, information about the place of IHCA and sur- vival was in agreement with source data in 99% of cases. Information on witnessed status was in agreement with source data in 96% of cases. Information on the type of first recorded arrhythmia was in agreement with source data in 94% of cases.

Statistical methods

Age among women and men was compared using the Mann-Whit- ney U test. All other comparisons between the genders were (actual) age adjusted using logistic regression and presented in the tables as odds ratios for men versus women, with corresponding 95% confidence intervals and p-values. Multivariate logistic regression was also used to adjust for, in addition to age, previous history, etiology and initial rhythm when comparing men and women in terms of 30-day survival. This was done both with complete data and, due to the extent of missing data for several of these variables, also using multiple imputations. The latter was regarded as the primary analysis in the study. Missing was as- sumed to be missing at random (MAR) and 50 imputed data sets were generated with the Markov Chain Monte Carlo (MCMC) method and using the expectation-maximization (EM) algorithm. Rubin’s rules were used to pool the results from the imputed data sets. The associa- tions between different factors and ordered age groups were tested using the Mann-Whitney U test. All tests are two-sided and a p-value of b 0.05 was considered statistically significant for the primary end- point of 30-day survival; otherwise, the significance level was set at p

Table 1

Patient characteristics.

All Women Men b50 50-64 >= 65

(n = 14,933)

(n = 5767)

(n = 9166)

p#

(n = 927)

(n = 2532)

(n = 11,474)

p?

+/-??

Age (years; mean +- SD)

72.7 +- 13.4

74.3 +- 13.8

71.7 +- 13.1

b 0.0001

39.4 +- 8.5

58.7 +- 4.2

78.5 +- 7.6

Women (%)

38.6

100

0

37.2

32.3

40.1

b0.0001

+

Previous history of (%)

Heart failure (11/12/11/10/10/12)a

35.9

32.3

1.43 (1.32, 1.54)##

b 0.0001

15.0

24.8

40.1

b0.0001

+

Diabetes (7/7/7/7/7/7)

25.9

24.3

1.09 (1.01, 1.18)

0.03

14.9

26.7

26.6

b0.0001

+

Myocardial infarction (10/11/10/9/10/11)

25.6

19.9

1.77 (1.62, 1.93)

b 0.0001

6.0

18.8

28.7

b0.0001

+

Stroke (8/8/7/7/7/8)

12.5

11.1

1.34 (1.20, 1.49)

b 0.0001

2.3

6.6

14.7

b0.0001

+

Respiratory insufficiency (8/8/8/8/9/8)

20.7

20.6

0.98 (0.90, 1.07)

0.63

12.4

18.2

21.9

b0.0001

+

Renal dysfunction (16/16/16/21/16/15)

65.3

66.1

1.13 (1.04, 1.23)

0.004

30.1

42.0

73.1

b0.0001

+

Ongoing disease (%)

Myocardial infarction (13/13/13/9/12/14)

29.1

26.1

1.30 (1.20, 1.40)

b 0.0001

16.0

28.9

30.2

b0.0001

+

Stroke (9/9/9/7/8/9)

3.3

3.3

1.02 (0.84, 1.24)

0.82

2.0

2.8

3.5

0.004

+

Time of OHCA (%)

Weekday 08-20 (2/2/3/3/3/2)

40.3

39.8

1.03 (0.97, 1.11)

0.34

40.0

42.5

39.9

0.06

Year of IHCA (%)

2011-2014

60.8

60.6

1.02 (0.95, 1.09)

0.61

61.3

58.9

61.2

0.11

# Age-adjusted p-value.

## Age-adjusted odds ratio (95% c.i.) for men versus women.

      • Ordered age group used in p-value calculation.

?? Denotes more frequent with increasing (‘+’) or decreasing (‘-‘) age group, given if p b 0.05..

a Percentage missing among all patients, women, men and the three age groups, respectively.

b 0.01, due to the sample size and the number of tests performed. All the analyses were performed using SAS for Windows v9.3.

Funding

No extramural funding was used to support this work. The authors are solely responsible for the design and conduct of this study, all study analyses and drafting and editing of the paper.

Ethics

The Ethical Board in Gothenburg approved this study. The number of the approval is 668-16.

  1. Results
    1. Descriptions of IHCA events with regard to gender

The 14,933 IHCA events are presented in Tables 1 to 6. The mean age was 72.7 years. Women constituted 38.6% and were significantly older than men (Table 1). Renal dysfunction was reported in 65.3% of all pa- tients. Heart failure was the second most common co-existing condition (35.9%), followed by previous MI (26.6%) and diabetes (25.9%). Heart failure, MI, stroke and renal dysfunction were significantly more com- mon in men.

Almost one third of all patients had an on-going MI, which was sig- nificantly more common in men. Forty percent of the IHCA events oc- curred during the daytime on a working day. A significantly lower proportion of men had their IHCA in the operating room and almost 50% of arrests occurred on general wards, with no significant gender dif- ference (Table 2).

Myocardial infarction was the most common condition preceding IHCA in our study (33.4%). The age-adjusted odds of having MI as the underlying cause was 27% higher for men compared with women. Ar- rhythmia was the second most common condition preceding IHCA (25.8%), with no significant gender difference. Respiratory insufficiency (11.6%) was significantly less common in men than in women (Table 3). Fifty percent of the cases were ECG monitored and 80.6% of the events were witnessed. No significant gender differences were noted

for either of these two parameters.

A shockable initial rhythm was found in almost one third of the pa- tients, with men having N 50% higher odds of being found in VT/VF, as compared with women (Table 4). This was not changed when adjusting for MI as the underlying etiology for IHCA (data not shown). No signif- icant gender differences were found with regard to the delay in calling the rescue team, starting CPR, defibrillation, or the arrival of the rescue team. In terms of treatment, men had almost 40% higher odds of receiv- ing anti-arrhythmic drugs compared with women (Table 4). No signifi- cant differences between men and women were noted with regard to intubation, the use of adrenalin, or the use of other vasopressors.

Table 2

Place of IHCA (%).

All Women Men b50 50-64 >=65

(n = 14,933) (n = 5767) (n = 9166) p# (n = 927) (n = 2532) (n = 11,474) p? +/-??

Coronary care unit

16.9

15.9

1.12 (1.03, 1.23)##

0.01

11.6

15.8

17.6

b 0.0001

+

Angiography laboratory

7.1

6.3

1.11 (0.97, 1.27)

0.12

7.1

10.9

6.2

b 0.0001

Intensive care unit

8.5

8.0

0.98 (0.87, 1.11)

0.77

16.5

12.3

7.1

b 0.0001

Operating room

2.0

2.3

0.64 (0.50, 0.82)

0.0004

3.7

2.3

1.5

b 0.0001

Emergency department

9.5

9.4

1.02 (0.91, 1.15)

0.68

12.9

11.0

8.9

b 0.0001

General wards

49.8

51.8

0.95 (0.89, 1.02)

0.12

39.3

39.8

52.8

b 0.0001

+

Lab, radiology department, etc.

3.8

4.0

0.88 (0.74, 1.05)

0.15

4.1

4.7

3.6

0.02

Other

2.6

2.4

1.08 (0.87, 1.33)

0.50

4.9

3.2

2.2

b 0.0001

# Age-adjusted p-value.

## Age-adjusted odds ratio (95% c.i.) for men versus women.

      • Ordered age group used in p-value calculation.

?? Denotes more frequent with increasing (‘+’) or decreasing (‘-‘) age group, given if p b 0.05.

Table 3

Etiology (%) (21/23/21/17/19/22)a.

All Women Men b50 50-64 >= 65

(n = 14,933) (n = 5767) (n = 9166) p# (n = 927) (n = 2532) (n = 11,474) p? +/-??

Arrhythmia

25.8

25.1

1.07 (0.98, 1.16)##

0.14

22.5

25.3

26.2

0.06

Myocardial ischemia/infarction

33.4

30.4

1.27 (1.18, 1.38)

b0.0001

21.1

33.6

34.5

b0.0001

+

Respiratory insufficiency

11.6

12.8

0.81 (0.72, 0.91)

0.0004

12.9

10.8

11.6

0.86

Hypotension

7.2

7.6

0.90 (0.78, 1.03)

0.13

7.2

6.9

7.2

0.60

acute pulmonary edema

4.0

4.0

1.02 (0.84, 1.24)

0.84

2.6

3.5

4.2

0.02

+

# Age-adjusted p-value.

## Age-adjusted odds ratio (95% c.i.) for men versus women.

* Ordered age group used in p-value calculation.

?? Denotes more frequent with increasing (‘+’) or decreasing (‘-‘) age group, given if p b 0.05.

a Percentage missing among all patients, women, men and the three age groups, respectively.

Almost one third of the patients survived to hospital discharge and to 30 days after cardiac arrest.

Ninety-three percent of survivors had a CPC score of 1-2 at discharge from hospital, with no significant difference between genders.

Table 6 illustrates that, when adjusting for several potential con- founders and using multiple imputations to handle the missing data problem, male gender was associated with significantly lower 30-day survival. This was the primary endpoint of the study.

Descriptions of IHCA events with regard to age

As expected, a history of each of the studied co-morbidities was significantly associated with increasing age. The proportion of on- going MI at the time of the arrest was nearly doubled when compar- ing patients younger than 50 years of age with the older age groups (16.0%, 28.9% and 30.2% respectively). Similarly, on-going stroke was also significantly associated with increasing age. No significant association with age was noted with regard to the time of the arrest (Table 1).

The place of cardiac arrest was significantly associated with age, in that arrests occurring on general wards and at the coronary care unit were more common with increasing age (Table 2).

Myocardial infarction as the underlying condition immediately be- fore IHCA was significantly associated with higher age (Table 3).

Despite the finding of more co-morbidity with increasing age, ECG monitoring was significantly associated with lower age. There was also a significant association between both witnessed arrests and VT/ VF as the first recorded arrhythmia and lower age (Table 4).

A non-significant trend towards a longer delay to call the rescue team was noted with increasing age. Among patients with VF/VT as the initial rhythm, an extended time to defibrillation was significantly associated with increasing age (Table 4). Neither time to call, to the start of CPR nor to the arrival of rescue team was significantly associated with age group.

Intubation, vasopressors and anti-arrhythmic drugs were utilized less frequently with increasing age (Table 4). No significant association was found regarding the use of adrenalin.

As expected, there was a significant inverse association between sur- vival to discharge and 30-day survival and increasing age (Table 5). However, there was no significant association between age group and CPC score at discharge from hospital among survivors.

  1. Discussion

In this study of 14,933 cases of IHCA, we examined the incidence and outcome of IHCA from an age and gender perspective, covering the ma- jority of hospital beds in Sweden. This increases the generalizability of the results obtained, as Regional variations have been shown to influ- ence incidence and survival after IHCA [27].

Table 4

Peri-arrest conditions.

All Women Men b50 50-64 >= 65

(n =

(n =

(n = 9166)

p#

(n =

(n =

(n =

p?

+/-??

14,933)

5767)

927)

2532)

11,474)

ECG monitored (%) (3/3/3/4/4/3)b

50.1

47.9

1.08 (1.01,

1.15)##

0.03

55.2

56.5

48.2

b0.0001

Witnessed (%) (2/2/2/1/2/2)

80.6

80.3

0.96 (0.88, 1.05)

0.39

84.9

85.1

79.2

b0.0001

VF/VT as initial rhythm (%) (24/26/23/22/21/25)

31.8

25.6

1.52 (1.40, 1.65)

b0.0001

33.3

39.3

30.0

b0.0001

Delay (%)

CA to call N 1 min (21/20/21/28/25/19)

20.8

21.2

0.98 (0.89, 1.07)

0.62

19.3

19.2

21.2

0.03

+

CA to start of CPR N 1 min (15/15/16/18/17/15)

11.7

12.2

0.94 (0.84, 1.05)

0.26

12.6

11.3

11.7

0.98

CA to defibrillation N 3 min (19/20/19/21/19/19)a

18.2

19.1

0.96 (0.78, 1.18)

0.71

13.0

14.2

19.8

0.0002

+

Call to arrival of rescue team N 2 min

46.1

45.8

1.02 (0.95, 1.10)

0.61

44.5

47.5

45.9

0.55

(22/21/23/28/26/21)

Treatment (%)

Intubation (4/3/4/5/4/3)

50.3

49.8

0.96 (0.90, 1.03)

0.22

63.9

54.3

48.3

b0.0001

Adrenalin (3/3/3/2/3/3)

66.4

66.4

0.98 (0.92, 1.06)

0.67

66.3

65.5

66.6

0.38

Other vasopressors (11/10/11/12/11/10)

10.6

10.3

0.98 (0.88, 1.10)

0.78

17.1

12.2

9.8

b0.0001

Antiarrhythmics (10/10/10/10/10/10)

15.9

12.8

1.39 (1.25,1.53)

b0.0001

19.1

19.8

14.8

b0.0001

# Age-adjusted p-value.

## Age adjusted odds ratio (95% c.i.) for men versus women.

* Ordered age group used in p-value calculation.

?? Denotes more frequent with increasing (‘+’) or decreasing (‘-‘) age group, given if p b 0.05.

a Only patients with VF/VT as initial rhythm.

b Percentage missing among all patients, women, men and the three age groups, respectively.

Table 5

Survival and CPC.

All Women Men b 50 50-64 >= 65

(n = 14,933) (n = 5767) (n = 9166) p# (n = 927) (n = 2532) (n = 11,474) p? +/-??

Discharged alive (%) (3/3/3/4/3/2)a 28.0

25.8

1.09 (1.01, 1.18)##

0.03

45.2

39.3

24.2

b 0.0001

Discharge CPC 1-2 (%)

Of those discharged alive (13/13/14/13/12/14) 93.2

92.5

1.12 (0.85, 1.47)

0.42

91.1

94.4

93.1

0.98

Of all patients (6/6/6/10/8/6) 23.5

21.5

1.09 (1.01, 1.19)

0.03

37.9

34.2

20.1

b 0.0001

30-day survival (%) (0.2/0.1/0.2/0.4/0.4/0.1) 28.1

26.3

1.05 (0.97, 1.13)

0.24

46.0

39.5

24.2

b 0.0001

# Age-adjusted p-value.

## Age-adjusted odds ratio (95% c.i.) for men versus women.

* Ordered age group used in p-value calculation.

?? Denotes more frequent with increasing (‘+’) or decreasing (‘-‘) age group, given if p b 0.05.

a Percentage missing among all patients, women, men and the three age groups, respectively.

IHCA and gender

Previous reports have produced conflicting results, as to whether fe- male gender predisposes to better survival after both OHCA and IHCA. When adjusting for several potential confounders, we found that male gender was associated with a 10% decrease in 30-day survival as com- pared with female gender. This finding is in agreement with several pre- vious studies [3,5,28,29]. The mechanisms behind this finding can only be speculated on, but it has been hypothesized that female sex hormones might play a role in protecting from ischemic-reperfusion in- jury and limiting post-resuscitation tumor necrosis factor-? response [30,31]. Other studies, however, have not demonstrated any gender ad- vantage in terms of survival in either OHCA or IHCA, especially in older women [4,17,21,32]. The reason for this discrepancy needs to be evalu- ated in future research.

We found that men had more indicators of coronary artery disease than women. This could potentially explain why women represent only 39% of the reported IHCA cases, since coronary artery disease has been shown to increase the risk of sudden cardiac death in a hospital setting [33]. This further underlines the fact that myocardial ischemia should be suspected at an early stage among men with IHCA of un- known etiology. This may expedite potentially Life-saving interventions such as acute coronary angiography.

We did not observe any gender differences regarding the time to calling for the rescue team, starting CPR, defibrillation, or the arrival of the rescue team. This is in agreement with previous studies [3,4,34]. Our results suggest that cardiac arrest in women is less likely to be of cardiac etiology and that other causes should be considered. In fact, women who suffer OHCA have been shown to have less cardiac disease in their previous medical history. Furthermore, they are less likely to be found in VF and have a greater chance of arriving at hospital alive [29].

IHCA and age

Our finding of a clear association between increasing age and poor outcome is consistent with most studies that identified an inverse yet

linear relationship with age and survival in IHCA [6,35]. However, we found no association between increasing age and CPC score among those discharged from hospital alive. To our knowledge, there have been no studies examining the relationship between increasing age and CPC score in survivors after IHCA.

Older patients were less likely to be ECG monitored and the delay to defibrillation increased with increasing age. We also found that intuba- tion and medications, such as vasopressors and anti-arrhythmic drugs, were less frequently used among the elderly, despite the fact that they displayed substantially higher co-morbidity and higher mortality. These findings are in agreement with previous reports [36,37] and prob- ably indicate a lower use of monitoring and a lower use of therapeutic interventions in older patients. This might be due to the belief that the chance of survival is lower among the elderly. In this perspective, it is important to note that older patients who survived an IHCA had a CPC score similar to that of younger patients.

Strengths and limitations

This is one of a few studies, which aim to describe IHCA from a na- tionwide perspective, covering the majority of hospital beds in a single country. As with all register studies, data on certain variables were miss- ing. The proportion of missing data was as high as 25% for certain vari- ables. However, multiple imputations were performed in an attempt to compensate for missing data.

Our way of using age groups, instead of actual age, when analyzing associations with age can be discussed. We have previously used the same type of subdivision among patients with acute chest pain [38]. The age-group limits can be justified as representing relatively young patients (b 50 years), those in the middle part of life (50-64 years) and those who reached the age at which many people retire from work. The overall prevalence of renal dysfunction was surprisingly high. This is best explained by the combination of previous renal dys- function and Hemodynamic deterioration in association with the cardi- ac arrest.

Table 6

Multivariate analysis of 30-day survival in relation to sex.

Adjusted for age, previous history, etiology and initial rhythm using complete datab

OR (95%

c.i.)a

0.96 (0.85,

1.09)

p

0.53

  1. Conclusion

When adjusting for various confounders, as well as missing data, we found that men had a 10% lower chance than women of surviving to 30 days. Older individuals were managed less aggressively than their younger counterparts, despite a lower chance of survival.

Unadjusted for these patientsb 1.20 (1.08,

1.32)

0.0005

Higher age was not associated with poorer cerebral function among survivors.

Adjusted for age, previous history, etiology and initial

rhythm using multiple imputationsc

0.90 (0.83,

0.99)

0.03

a Odds ratio for men in relation to women with corresponding 95% confidence interval, regarding 30-day survival.

b (n = 7214 with known survival status at 30 days: 2676 women, 4546 men).

c (n = 14,908 with known survival status at 30 days: 5763 women, 9145 men).

Conflicts of interest

None.

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