Single-center In-hospital Cardiac Arrest Outcomes

INTRODUCTION

Sudden cardiac arrest is defined by the American College of Cardiology and American Heart Association (AHA) as, “sudden cessation of cardiac activity so that the victim becomes unresponsive, with no normal breathing and no signs of circulation.”^1,2 It is estimated that approximately 292,000 adult IHCAs are treated annually in the United States.³ The AHA identifies hypovolemia, hypoxia, hydrogen ion (acidosis), hypokalemia, hyperkalemia, hypothermia, tension pneumothorax, cardiac tamponade, toxins, pulmonary thrombosis, and coronary thrombosis as reversible etiologies of cardiac arrest to include, which are colloquially known as the H’s and T’s.⁴ Studies have described the etiology prevalence of in-hospital cardia arrest (IHCA) in the United States; however, there are limited data describing the patient characteristics and patterns in survivability with relation to length of stay (LOS), etiology, and primary service.^5–10 We aimed to describe the patient characteristics, survivability of IHCA as well as survival to discharge, and the effect different parameters have on predicting survival.

MATERIALS AND METHODS

This study was approved by the Institutional Review Board (201702489) for the University of Florida Health (Gainesville, Florida, USA), which is a tertiary care center with over 950 beds. We carried out a single-center retrospective chart review of patients admitted from January 1, 2012, to December 31, 2017 who had the principal diagnosis of cardiac arrest after presentation to the hospital. Our institutional review board waived the need for written informed consent. The inclusion criteria were both males and females who were between 18 years and 90 years of age who had a cardiac arrest after presentation to the hospital and received full resuscitative measures according to the AHA’s advanced cardiac life support (ACLS).⁴ The exclusion criteria were patients undergoing cardiopulmonary resuscitation at the time of arrival or before arrival to the hospital or did not receive full resuscitative measures according to ACLS.⁴ In cases where a patient experienced more than one IHCA during a hospitalization, only the initial IHCA event was evaluated.

All clinical data were extracted from the patient’s records, including age, gender, body mass index (BMI), primary admitting service, admission etiology, IHCA etiology, and LOS until IHCA, survival of IHCA, and survival to hospital discharge. In-hospital cardiac arrest etiology was categorized into eight groups, such as pulmonary, cardiac, exsanguination, aortic injury, metabolic, cerebral, adverse drug reaction, or unknown¹¹ (Table 1). Patients were designated to one of these groups by identifying documentation of the etiology by the primary healthcare team or upon autopsy. If an autopsy and the primary healthcare team did not identify an etiology, then the IHCA etiology was assigned as unknown. No autopsies or tests were performed for the sole purpose of this study.

STATISTICAL ANALYSIS

Demographic and clinical characteristics of patients were evaluated with between-group differences. We used paired t test to analyze the effects of sex, age, BMI, LOS, and admitting service over survival of IHCA and survival to discharge. To examine the association between survival of the arrest and survival to discharge and known cofounders, multivariable logistic regression analysis was used with survival as the exposure variable. The model included important cofounders, including age, sex, BMI, hospital service, and days of hospitalization before the arrest. All p values represent 2-sided hypothesis test. The significance level for all test was alpha <0.05. Analysis were performed with GraphPad Prism, version 7.0 (GraphPad Software Inc., La Jolla, California).

RESULTS

DISCUSSION

This study demonstrated the frequency and outcomes of IHCA analyzed by BMI, age, LOS, gender, etiology of IHCA, and whether patients were admitted to a surgical or nonsurgical service. As described in previous studies, the occurrence of an IHCA portends a poor prognosis with 79.5% of patients surviving the initial IHCA and ultimately only 32.4% of all patients surviving to discharge in our study.^5,6,11–13 When our population was evaluated by gender, BMI (<30 kg/m² or ≥30 kg/m²), age (≤60 or %3E;60 years), and LOS until IHCA (<9 days or ≥9 days), there was no difference in outcomes at discharge. Persons aged ≤60 years were more likely to survive the initial IHCA; however, there was only a trend for improved survival to discharge.

Individuals with the initial IHCA occurring in the MICU had the poorest outcomes compared with all other groups with only 20.2% surviving to discharge, which is similar to the rates published previously.⁹ Expectedly, patients admitted to the MICU have more comorbidities, acute organ failure, history of cancer, presence of mechanical ventilation, and/or use of vasoactive medications, which are established associations with not surviving to discharge after IHCA.⁹

There was an improved outcome for survival to discharge for patients admitted to surgical compared with medical services. We postulate the etiology of IHCA, average LOS, and level of acuity may contribute to this. Our model was able to confirm that shorter LOS has the highest weight predicting who will survive the arrest regardless of any other variable. Unknown causes of IHCA led to 148 cases (54.6%) on nonsurgical services compared with 101 cases (43.9%) on surgical services, with a between-group percent difference of 10.7%. This discrepancy is a direct reflection of the lack of identifying a cause and possibly a lack of identifiable treatment. We also suspect that there may have been a difference in the level of acuity, complexity of comorbidity, and mortality risk for surgical vs nonsurgical patients. If the data was available to evaluate each patient for Acute Physiology and Chronic Health Evaluation II or Sequential Organ Failure Assessment score, we may have been able to investigate this further.

Length of stay also contributed to patient outcomes. As LOS increased, there was a larger proportion of IHCA attributed to pulmonary and metabolic etiologies; conversely there was a downward trend in the percentage of cardiac and cerebral etiologies. This is similar to previous data describing the increased proportion of pulmonary etiologies as LOS increased.¹⁰ After adjusting for BMI, age, gender, and whether the patient was on a surgical or nonsurgical service, there was a significant increase in mortality following the initial IHCA as LOS increased. An international review of over four million admissions also found a correlation between increased LOS and mortality.¹⁴ We postulate these factors may be related to patient comorbidities, hospital-acquired aspiration, adverse in-hospital events, and hospital-acquired infections. With these data, healthcare providers should consider these pulmonary and metabolic etiologies more frequently in IHCA occurring in patients with a LOS ≥9 days. Although monitoring in itself does not reduce the number of IHCA, the upward trend in the number of pulmonary etiologies identified in our population highlights the importance of monitoring oxygenation with the hope to more quickly identify and intervene on a pulmonary etiology for IHCA.

Our study used a similar approach to grouping the IHCA etiology to previous studies; however, there is variation in the literature of how this is categorized.^4,10–12 When an identifiable etiology for IHCA was determined by the primary healthcare team, it was most commonly a pulmonary or cardiovascular cause consistent with prior investigations.^10–12 We offer that a multi-society approved definition of different categories of causes and etiology will allow for more structured investigation and reporting, and potentially practice changing.

This study has multiple limitations, including a single-center academic institution with unique locoregional pathology. It has been established that regional differences, race, vasoactive medications, mechanical ventilation, age ≥65 years old, timing (night and weekend), trauma centers, and teaching hospitals are associated with different cardiac arrest incidence and case survival.^5,6,9 Witnessing the cardiac arrest and ratio of nurses to patients impact survival, which may play a role in our outcomes, but we were unable to identify what proportion of the IHCA occurred in and out of an intensive care setting to investigate this further.⁵ Also, some subgroups have lower sample size and are at risk for type II errors. Our study relied on direct documentation by the primary team or autopsy interpretation to decide the etiology of IHCA, which may be incorrect or incomplete and subsequently leading to confounding results. This raises the question again, if standardized documentation following a IHCA may provide more data and guide further studies.^15,16

CONCLUSION

In-hospital cardiac arrest portends a poor prognosis with only 32.4% of our patients surviving to discharge. There was a significant difference in the outcome to discharge in favor of patients admitted to a surgical service compared with nonsurgical service. These findings are hypothesis-generating and further clinical trials should evaluate this further.

ETHICS APPROVAL AND CONSENT TO PARTICIPATE

The need for approval to participate was waived by our institutional review board.

REFERENCES

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