Investigation of mortality rates and the factors affecting survival in out-of-hospital cardiac arrest patients

Abstract Background It is known that even if spontaneous circulation returns after cardiopulmonary resuscitation(CPR) in geriatric out-of-hospital cardiac arrests(OHCA), the overall one-year survival rate of these patients is very low. In our study, we aimed to investigate the factors affecting survival in OHCA cases. Methods OHCA patients over 18 years of age were examined in two different groups as 18–64 years old and over 65 years old. Demographic data, comorbidities, cardiac arrest rhythms and minutes, and the number of days they were hospitalized in the intensive care unit were recorded. Results The mean age was 65.9 ± 15.8 years and 39.9% (n = 110) of the patients were female. The number of intensive care unit stays was significantly higher in the over-65 age group (p = 0.011). The mortality rate and one-year survival rate were significantly lower in the over-65 age group (p < 0.001). Median CPR time was 21 min (IQR:14–32) in the entire patient population. The duration of CPR was 22 min (IQR:14–35) in patients with in-hospital mortality, and 15 min (IQR:13–25) in patients discharged from the hospital. In this comparison, the difference is statistically significant (p = 0.008). Conclusion In our study, it was determined that especially over 65 years of age, coronary artery disease, and post-arrest CPR duration were determinant and predictive factors in in-hospital and long-term survival.


Introduction
Cardiopulmonary resuscitation (CPR) is the treatment for the potentially fatal cardiac arrest.Unfortunately, the success rates of CPR are poor.The percentage of patients discharged from hospitals following the procedure ranges from 0% to 20%, and these rates have not improved significantly over the past 30 years.The reasons for this can be listed as the increasing age of the population, the frequency of out-of-hospital cardiac arrests, and the decreasing incidence of ventricular fibrillation rhythm [1,2].
With increasing age in the geriatric population, the prevalence of disease and disability clearly increases, while perceived health status and physical well-being decrease [3].Given how low the probability of survival with an acceptable quality of life after CPR is, the question arises as to whether it is suitable for elderly patients with limited life expectancy and multiple diseases.
It is known that even if spontaneous circulation returns after cardiopulmonary resuscitation in geriatric cardiac arrests, the overall one-year survival rate of these patients is very low [4].It has been emphasized in many studies that the most important factor affecting survival is the duration of cardiac arrest and age.In our study, we aimed to investigate the factors affecting survival in out-of-hospital cardiac arrest cases.

Materials and methods
The study was conducted after obtaining approval from the Eskis ¸ehir Education and Training Hospital of Medicine Non-Interventional Clinical Research Ethics Committee (Date:10.05.2023Decision No:16).All procedures were carried out in accordance with the ethical rules and the principles of the Declaration of Helsinki.

Study population
In our study, out-of-hospital cardiac arrest cases over the age of 18 who applied to the Emergency Department of Eskis ¸ehir City Hospital were examined.Out-of-hospital cardiac arrest patients under the age of 18 and inpatient cardiac arrest patients were excluded from the study.In our study, cardiac arrest patients over 18 years of age were examined in two different groups 18-64 years old and over 65 years old.

Data collection
Demographic data, comorbidities, cardiac arrest rhythms, cardiac arrest duration, number of days stayed in the intensive care unit, mortality status, and one-year survival were recorded retrospectively.

Statistical analysis
The normality of the distributions of continuous variables was checked with the Shapiro-Wilk test, and the homogeneity of group variances was checked with the Levene test.Since descriptive statistics did not show a normal distribution for continuous variables, the median was interquartile range; was expressed as the number of cases and (%) for categorical variables.In the comparisons of the two groups, categorical variables were compared with the chi-square test, and continuous data that did not show normal distribution were compared with the Mann Whitey-U test.Binary logistic regression analysis was used to evaluate the factors affecting survival.SPSS 20.0 statistical package program was used in the analysis of the data set.

Results
The mean age was 65.9 ± 15.8 years and 39.9% (n ¼ 110) of the patients were female.When we examined in terms of comorbidities, it was seen that diabetes mellitus, respiratory diseases, kidney failure, and neurological diseases were higher in the geriatric patient group (p < 0.001, p ¼ 0.025, p < 0.001 and p < 0.001, respectively).There were no statistically significant difference in terms of cardiac rhythms among study groups (p > 0.05).The number of intensive care unit stays was significantly higher in the over-65 age group (p ¼ 0.011).The mortality rate and one-year survival rate were significantly lower in the over-65 age group (p < 0.001).When the inhospital survival of the patients was examined, the discharge rate was found to be 18.5% (n ¼ 51) (Table 1).
In the study, the median CPR time was 21 min (IQR: 14-32) in the entire patient population.The duration of CPR was 22 min (IQR: 14-35) in patients with in-hospital mortality, and 15 min (IQR: 13-25) in patients discharged from the hospital.In this comparison, the difference is statistically significant (p ¼ 0.008).Age and coronary artery disease were found to be significant predictors of mortality (p < 0.001, p ¼ 0.027, respectively) (Table 2).

Discussion
In this study, we aimed to determine the short-and long-term predictors of mortality in patients who survived out-of-hospital cardiac arrest and were hospitalized after the intervention.At the end of the study, it was determined that the most important predictors of mortality were age, history of coronary artery disease, and duration of CPR.When the patient groups under 65 and over 65 years of age are compared, it is seen that there is a substantial difference between the age groups, especially in hospital and one-year survival.
Cardiopulmonary resuscitation has been started to be applied since the 1950s and is the most important treatment method applied in cardiac arrest patients [5].Unfortunately, survival rates are not very high in these patients despite CPR.Survival is low, especially in OHCA [6].Although it varies from region to region, the rates of discharge from the hospital in these patients vary between 0.3% and 20.4% [2,7,8].In our study, the discharge rate was found to be 18.5% in patients who were brought to the emergency room after OHCA and then hospitalized in the intensive care unit.These results are in a similar range to the rates reported in other studies.Considering that 80% of the patients who were arrested outside the hospital and hospitalized in the intensive care unit were comatose and two-thirds of these patients resulted in death due to hypoxic ischemic brain injury, questions such as should we perform CPR on all of these patients, and which patients should we perform CPR on, are on the minds of doctors and health personnel [9][10][11].Many factors affect the survival rates of OHCA patients.Factors related to the external environment such as witnessed arrest, CPR training of the surrounding individuals, and CPR application, the arrival time of the ambulance to the scene affect the chance of success, and patient-related factors are also effective in achieving CPR success and spontaneous rhythm [2].Age comes to the fore in personal factors affecting the survival rate of OHCA patients [6].With advancing age, cell-based changes and deterioration begin in tissues and organs [12].With negative changes in the body, morbidity and disability increase, and the well-being of the body deteriorates [13,14].As age progresses, hospital discharge rates also decrease in OHCA patients.Swor et al. found the rate of hospital discharge in OHCA patients aged 40-49 and 50-59 years to be around 10%.In patients over 65 years of age, especially if the cardiac arrest occurred at home and the rhythm was unshockable, it was determined that the 30-day survival decreased very dramatically [15].However, as the age range progresses, survival rates decrease, and this rate drops to 3.3% over the age of 80 [16].In the study of Kuilman et al. in which they examined the 8-year follow-up of OHCA patients, age was also seen as one of the few parameters predicting long-term survival [17].In a meta-analysis, it was determined that the survival rate after the arrest decreases exponentially as the age increases, especially after the age of 70, even in in-hospital cardiac arrests [1].In our study, the emphasis on age was more prominent.In OHCA patients over 65 years of age, the rate of discharge from the hospital was only 1.3% in patients admitted to the intensive care unit after admission to the emergency department, while the one-year survival rate of these patients was 0.7%.In patients under 65 years of age, the rate of discharge from the hospital was 41.9%, and 1-year survival was 35%.So the difference is pretty obvious.Moreover, our study does not include patients who were treated at the scene or treated in the emergency room and were not hospitalized because they did not respond to CPR.In other words, when looking at the total number, the CPR response of those over the age of 65 will be determined even less.In the study of Lombardi et al., the overall survival of all OHCA patients was found to be 1.4% in the whole population.The real question is, should these patients really undergo CPR?Is performing CPR on these patients cost-effective or time-effective?Is CPR really ethical for these patients?In previous studies, it was found that CPR results were not good, especially in elderly patients [18,19].Despite all the developments in CPR, it is a fact that the results of the CPR procedure are overestimated and negative results are underestimated [20].Of course, the most ideal option for making a CPR decision is to inform the patient about CPR beforehand, to inform the patient about the possible results of CPR, and leave this decision to the patient.In a study conducted with patients with end-stage renal disease, it was observed that the majority of patients before learning how the CPR procedure is performed were positive for CPR when it was deemed necessary, but after the training that showed how the CPR procedure was performed and informed them about the results, there was a significant decrease in the patients who had a positive attitude towards CPR [21].Of course, since it is almost impossible to know the preferences of OHCA patients about CPR in advance, this decision is left to the doctor and health personnel.
In our study, it was observed that the number of male patients was higher in OHCA patients, both in individuals over the age of 65 and in individuals under the age of 65.Awad et al. stated in their study that this result may be due to the protective effect of estrogen [22].The data that cardiac arrest outcomes are more mortal in men are also supported by similar studies [23,24].
The duration of cardiopulmonary resuscitation is one of the important determinants of survival in both OHCA and IHCA patients [15].Studies have shown that long cardiopulmonary resuscitation time does not have a positive effect on survival, especially if the underlying cause of arrest has not been determined [25].In these patients, neurological outcomes worsen as the duration of CPR increases [26,27].In a study of OHCA patients, the survival rate was less than 1% in patients with a CPR duration of more than 33 min [15].In our study, similar to other studies, the effect of CPR duration on mortality was determined, and CPR duration was found to be statistically different between mortality and survivor groups.In addition, our study showed that apart from age, CPR duration is also a predictor of in-hospital mortality in OHCA patients.
There are different results in studies examining the effects of comorbidities on outcomes after cardiac arrest.While there are studies stating that comorbidities have a negative effect on mortality in these patients, there are studies stating that some comorbidities have no effect at all and some have positive effects [1, [28][29][30].Andrew et al. found out that the worst prognosis was seen in patients with congestive heart failure, diabetes mellitus [31].According to the guidelines, having a known diagnosis of heart disease is an independent risk factor for OHCA [32].In our study, when the pre-arrest comorbidities of the patients were examined, it was found that only cardiovascular diseases stood out as the predictor of mortality.This result is an expected result considering the general literature knowledge.

Limitations of the study
In our study, the arrest etiologies of the patients were not investigated.In addition, the characteristics of inhospital cardiac arrests and out-of-hospital cardiac arrests were not compared.

Conclusion
In our study, it was determined that especially over 65 years of age, coronary artery disease, and postarrest CPR duration were determinant and predictive factors in in-hospital and long-term survival.We think that our study contributes to the literature on survival rates in geriatric cardiac arrest patients.It is a pioneering study in order to guide health policies regarding the legal duration of cardiopulmonary resuscitation especially in geriatric patients.

Table 1 .
Demographic and Clinical characteristic of the patients.
CPR: cardiopulmonary resuscitation; ICU: intensive care unit; APACHE-II: acute physiology and chronic health evaluation -II score; EDR : expected death rate.

Table 2 .
Binary logistic regression analysis using forward: conditional method on the risk factors associated with mortality for cardiac arrest.