IHCA: Catching up with Advances Made in Out-Of-Hospital Cardiac Arrest

Disclosure: Dr. Nolan is Editor-in-Chief of Resuscitation.
Pub Date: Monday, March 11, 2013
Author: Jerry Nolan, FRCA, FRCP, FCEM, FFICM
Affiliation: Consultant in Anaesthesia and Intensive Care Medicine, Royal United Hospital, Bath, United Kingdom

Morrison LJ, Neumar RW, Zimmerman JL, Link MS, Newby LK, McMullan PW Jr, Vanden Hoek T, Halverson CC, Doering L, Peberdy MA, Edelson DP; on behalf of the American Heart Association Emergency Cardiovascular Care Committee, Council on Cardiopulmonary, Critical Care, Perioperative and Resuscitation, Council on Cardiovascular Nursing, Council on Clinical Cardiology, and Council on Peripheral Vascular Disease. Strategies for improving survival after in-hospital cardiac arrest in the United States: 2013 consensus recommendations: a consensus statement from the American Heart Association. Circulation. 2013: published online before print March 11, 2013, 10.1161/CIR.0b013e31828b2770.

Although we have a single set of guidelines for in-hospital cardiac arrest (IHCA) and out-of-hospital cardiac arrest (OHCA),^{1, 2} they are distinct entities. Out-of-hospital cardiac arrests usually have a primary cardiac cause and, although one study documented angina for a median of 2 hours before cardiac arrest among 25% of witnessed OHCAs,³ they are typically sudden events. In a study of the Resuscitation Outcomes Consortium (ROC) Epistry, 91.5% of 10,861 emergency medical services (EMS)--treated cardiac arrests were considered to be of cardiac etiology.⁴ In-hospital cardiac arrests occur typically in patients with significant comorbidities⁵; cardiac arrest is often a manifestation of a systemic critical illness. Approximately 80% will show evidence of deterioration in vital signs in the hours leading to cardiac arrest^{.6, 7} These fundamental differences between OHCA and IHCA imply the need for different strategies to improve survival. For this reason the consensus recommendations formulated by Morrison and colleagues are a welcome and valuable resource for healthcare providers and researchers with an interest in resuscitation, not just in the United States (US) but globally.

Determining the incidence of IHCA is important but if inter-hospital and international comparisons are to be made it is vitally important that both the denominator and numerator are standardized. The international resuscitation community has published uniform definitions for reporting the outcome of OHCA and IHCA, the Utstein style,⁹ but these do not provide enough detail to enable a standardized approach to reporting the incidence of IHCA. An update of the Utstein style is planned for 2013 and this may address this deficiency. In the meantime, Morrison and coauthors have proposed a recommended definition of incidence. They suggest that all patients admitted to critical care units, post anesthesia care units (PACUs), and operating rooms should be included in the denominator and that patients arresting in these areas are included in the numerator. Capturing data on all cardiac arrests occurring in operating rooms, critical care units, and PACUs is challenging. In many hospitals (particularly in the United Kingdom [UK], for example), the resuscitation team is not called to cardiac arrests in these areas, which makes it much more difficult to be sure that these events are all being included in the cardiac arrest registry. Such is this challenge in the UK, the National Cardiac Arrest Audit (NCAA) includes only cardiac arrests (requiring chest compressions and/or defibrillation) that lead to activation of the resuscitation team; thus many cardiac arrests are probably not included. In the 1 year from 1st April 2011 to 31st March 2012 approximately 18% of the 10482 cardiac arrests included in the NCAA database occurred in a critical care unit or coronary care unit (unpublished data). This contrasts strikingly with the Get With The Guidelines®-Resuscitation registry in which approximately 60% of cardiac arrests occur in an intensive care unit (ICU) and an additional 25% occur in a monitored unit.5 This reflects the huge difference between the US and the UK in ICU bed availability,¹⁰ as well as the failure to capture all ICU cardiac arrests in the NCAA database.

Despite these challenges, collecting data on the incidence of IHCA is inherently valuable. It could be argued that we should strive for the ideal of a zero incidence of unanticipated IHCA. If those at risk of cardiac arrest can be identified, they can either be treated effectively to prevent cardiac arrest or, if resuscitation is unlikely to be successful, a do-not-attempt resuscitation (DNAR) decision can be implemented. The use of automated vital signs monitoring and calculation of early warning scores may enable rapid response teams to be alerted and avert cardiac arrest.¹¹ Rapid response teams have a significant role in implementing DNAR decisions: A recent study documented that treatment limitation issues arose in one-third of medical emergency team (MET) calls.¹² Assuming we can standardize the denominators and numerators, the trend in the incidence of IHCA should reflect both recognition and treatment of the critically ill and the effective implementation of DNAR policies. These factors also have a major influence on outcome from IHCA – indeed, probably far more than that made by the treatment given during and after a cardiac arrest. Morrison and colleagues have recognized this, and their first recommendation is that DNAR status should be established and documented for all patients admitted to the hospital.8 The authors of a 2-week audit of all IHCAs occurring in the UK made the same recommendation: “CPR status must be considered and recorded for all acute admissions,…”.¹³ Increasingly, DNAR policies are incorporating a ceiling of treatment or Physician Orders for Life Sustaining Treatment (POLST), which more positively documents the treatments that will be provided rather than focusing solely on what will not be provided (CPR).¹⁴ In their second recommendation, Morrison and coauthors make the welcome suggestion that all hospital staff be trained to recognize cardiac arrest. In the UK, many nurses and doctors undertake the Immediate Life Support (ILS) course, which includes training on recognition of the deteriorating patient as well as recognition and treatment of cardiac arrest.

Morrison and colleagues have recommended survival to 30 days, along with a functional measure of survival, as the preferred outcome. Although many would prefer to capture functional outcome at 6 months (there is evidence of significant change in function during the first 6 months after survival from cardiac arrest),¹⁶ data at discharge or 30 days are much easier to collect. However, if inter-hospital comparisons in the outcome from IHCA are to be made, appropriate risk adjustment is even more important than the timing of the outcome assessment. In contrast to one large study of IHCA that showed no change in unadjusted outcome from 1992 to 2005,¹⁷ a recent analysis of  Get With The Guidelines®-Resuscitation data documented an increase in risk-adjusted rates of survival to discharge (13.7% in 2000 to 22.3% in 2009; adjusted rate ratio per year, 1.04; 95% confidence interval [CI], 1.03 to 1.06; P<0.001 for trend).5 A risk adjustment model also has been developed for the UK NCAA (unpublished). Until these risk adjustment models have been developed and validated, interhospital comparisons should be interpreted with extreme caution or not made at all

There is some evidence that the use of feedback systems will improve the quality of CPR during OHCA but as yet there is no evidence that outcome is improved.¹⁸ The quality of in-hospital CPR has been shown to be poor,¹⁹ and it is likely that this can be improved with feedback systems. However, even though real time feedback systems are widely available, it is my impression that they are used only infrequently during in-hospital resuscitation in the UK. Following a national airway audit, which identified cases of probable unrecognized esophageal intubation during IHCA,²⁰ the use of capnography is being implemented widely by resuscitation teams. This may be the most convenient method for providing real time feedback on the quality of CPR

Over the last few years there have been many developments in post cardiac arrest treatment.²¹ Most of these apply to both IHCA and OHCA; however, Morrison and colleagues point out correctly that although targeted temperature management (TTM) is used by many clinicians after IHCA, the only high level evidence for this therapy relates to ventricular fibrillation (VF) OHCA.²² This makes it important to include data on the use of TTM after IHCA in national registries. Prognostication after cardiac arrest remains problematic, and this is equally true for comatose survivors of both OHCA and IHCA.²³ The guidelines that were based on data derived before the use of TTM are in urgent need of updating.²⁴ This is a task for the International Liaison Committee on Resuscitation (ILCOR).

Finally, Morrison and coauthors question the potential impact on IHCA survivors of the regionalization of OHCA treatment. Critical care clinicians working in non-cardiac arrest centers may become deskilled in treating post cardiac arrest patients and this will impact their ability to treat survivors of IHCA. This is an important observation and is one that applies internationally, not just in the US. In the UK, I think it would be unrealistic to consider transferring all IHCA survivors to a regional cardiac arrest center… but circumstances change with time!

This consensus statement on IHCA raises important issues and I concur with its recommendations. It is likely that those practicing outside of the US will consider implementing many of them. I support the proposal to consider developing separate guidelines for OHCA and IHCA and look forward to the debate at the international level!

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-- The opinions expressed in this commentary are not necessarily those of the editors or of the American Heart Association --