Cardiac Arrest in the Emergency Department
Disclosure: Michael Sayre serves on the boards of Take Heart America and The Sudden Cardiac Arrest Foundation. He receives some minor support from Medtronics Physio-Control and from Phillips Medical.
Pub Date: Wednesday, June 3, 2009
Author: Michael R. Sayre, MD
Cardiac arrest in the emergency department (ED) is a surprisingly little studied illness. In a recent report in Resuscitation, Kayser and colleagues used the American Heart Association (AHA)-sponsored National Registry of CardioPulmonary Resuscitation (NRCPR) database to evaluate the outcomes from cardiac arrest events that occurred in the EDs of 430 hospitals reporting over 6 years, beginning January 1, 2000. The principal finding was that survival from cardiac arrest was higher in EDs than any other location in hospitals. The overall discharge survival rate for EDs was 23% compared with 20% on inpatient, nonintensive care unit (ICU), heart monitored units (telemetry), 16% in ICUs, and 11% on general nonmonitored nursing units (floor). Neurologic outcomes were best following cardiac arrest in the ED as well. One might have predicted that survival from cardiac arrest in the ED might be lower than other hospital locations given that the ED patient is the least known to the hospital staff.
Why is survival better in the ED?
Kayser et al. evaluated almost 7,500 ED cardiac arrest events and offered some potential explanations for the relatively good survival among ED patients. An initial cardiac arrest heart rhythm of ventricular fibrillation or pulseless ventricular tachycardia (VF/VT) is more common among ED patients (29%) than ICU (25%), telemetry (25%), or floor patients (13%). Multiple investigations in different settings have documented that cardiac arrests due to VF/VT have a much higher survival rate than cardiac arrests with an initial rhythm of asystole or pulseless electrical activity.
Other patient characteristics were different as well. ED patients were much more likely to be in the midst of an acute myocardial infarction than patients in other hospital units. Thus, it is expected that the ED patients would have a higher proportion of VF/VT as the presenting rhythm, and consequently, higher survival rates. On the other hand, ED patients had a higher incidence of hypotension and shock than telemetry or floor patients but a lower incidence than ICU patients. ED cardiac arrest patients were younger and had fewer preexisting conditions reported than hospitalized cardiac arrest patients.
In a database like NRCPR, accurate measurement of time intervals is challenging. Patients in the ED were reportedly defibrillated more quickly than telemetry or floor patients. They received other interventions such as start of compressions and administration of epinephrine at about the same time after onset of the cardiac arrest as patients in other parts of the hospital.
Controlling for these measured variables is challenging, even with the large number of patients in the dataset. The authors performed a regression analysis and found that event location, age, initial arrest rhythm, count of preexisting conditions, electrocardiogram (ECG) monitoring in place before the event, and witnessed event independently predicted survival to discharge. Having a cardiac arrest in the ED location was an independent positive predictor of survival to discharge [odds ratios (OR) 0.74, 95% confidence intervals (CI) [0.67, 0.82], p <0.0001]. There is not sufficient detail in the dataset to determine if unmeasured patient characteristics or better processes of care account for the improved chances of survival.
How do ED cardiac arrest patients compare to patients with out-of-hospital cardiac arrest?
The fact that 23% of ED cardiac arrest patients survived to hospital discharge is better than nearly all reports of survival from out-of-hospital cardiac arrest. Nichol and colleagues reported in 2008 that there was substantial variation in survival among different emergency medical services (EMS) systems. The best location in that publication reported 16% of out-of-hospital cardiac arrest patients survived to discharge from the hospital while other locations ranged downward as low as 3%. Kayser and colleagues did not report on variation in survival among different EDs because the case count averages only about 17 cases per hospital. One would expect that survival in the ED should be higher than outside of the hospital because the response interval in the ED is quite short. However, there may be opportunities to further raise survival rates for ED cardiac arrest patients if similar variation in survival exists among hospitals as it does before hospital arrival.
What can the rest of the hospital learn from this report?
Improvement in survival from cardiac arrest is possible when attention to detail is emphasized. It is likely that the rest of the hospital can achieve better survival from cardiac arrest by focusing on early recognition of patient decompensation and subsequent prevention of cardiac arrest. Achieving shorter time to defibrillation is possible and would raise survival for the fraction of patients presenting in VF/VT elsewhere in the hospital. Although this report cannot tell us what effect experience has on outcomes for these patients, one reason ED patients do better than other hospital patients may be because cardiac arrest is a relatively frequent ED event compared to telemetry and floor locations. Perhaps the resuscitation team is more practiced as a result, and perhaps the presence of a physician at all times has an impact.
How will the 2005 AHA Guidelines for Cardiopulmonary Resuscitation (CPR) and Emergency Cardiovascular Care (ECC) impact survival in the ED?
This study by Kayser et al. analyzed data from January 2000 to December 2005, which preceded the implementation of the 2005 AHA Guidelines for CPR and ECC (published in November 2005). A number of reports analyzing cardiac arrest outside the hospital have documented a substantial increase in survival following the introduction of the 2005 AHA Guidelines for CPR and ECC. To date, there have not been large studies published about in-hospital cardiac arrest events. We can hope that, with increased emphasis on chest compressions, administration of a single shock for VF/VT, and decreased emphasis on early endotracheal intubation, there will be a similarly positive effect on survival from cardiac arrest in the ED. Future research will direct us to focus on what can be done better to improve outcomes and save more lives.
-- The opinions expressed in this commentary are not necessarily those of the editors or of the American Heart Association --