Survival vs. Functional Outcome: What Does Really Matter and How Do We Measure It in Resuscitation Science?
Disclosure: Dr. Cruz-Flores has modest Research Grant relationships with Axio, Biotronic, Quintiles, and Roche.
Pub Date: Monday, Oct. 3, 2011
Author: Salvador Cruz-Flores, MD, MPH, FAHA
Affiliation: Saint Louis University
Becker LB, Aufderheide TP, Geocadin RG, Callaway CW, Lazar RM, Donnino MW, Nadkarni VM, Abella BS, Adrie C, Berg RA, Merchant RM, O’Connor RE, Meltzer DO, Holm MB, Longstreth WT, Halperin HR; on behalf of the American Heart Association Emergency Cardiovascular Care Committee and the Council on Cardiopulmonary, Critical Care, Perioperative and Resuscitation. Primary outcomes for resuscitation science studies: a consensus statement from the American Heart Association. Circulation. 2011, published online before print October 3, 2011, 10.1161/CIR.0b013e3182340239.
It is said that what is not measured cannot be fixed. While many lives have been saved, cardiac arrest remains a leading cause of death in the United States. This is despite the American Heart Association's (AHA) Chain of Survival that includes immediate public recognition and activation of the emergency response system (by calling 9-1-1); early CPR, usually performed by a bystander; easy and rapid access to public defibrillation; effective advanced life support by emergency medical service providers; and an integrated and organized hospital post-cardiac arrest care, which now includes therapeutic hypothermia.1, 2 In fact, a recent consensus of experts on improving cardiac arrest survival proposed to systematically measure implemented interventions to improve survival, supporting the idea that measurement leads to changes for improvement.3 However, when embarking on a quest to improve care we have to ask ourselves what we want to improve and how we are going to know if we achieved our goal. This is particularly important in the design of randomized clinical trials (RCT). In resuscitation science, some hard endpoints such as death or survival are easy to measure and do not need elaborate definitions. However, in this era of increasing patient-centered care, survival is not the only outcome patients are interested on. Quality of life, neurological and cognitive functions may be more important given the probability of neurological impairment among survivors of cardiac arrest. Measuring these constructs requires not only valid and reliable tools but also an agreement about time points where measures will be evaluated considering that the condition after the arrest or upon discharge may not predict the outcome at 3 or 6 months.
It is clear that survival depends on the timely restoration of cardiac rhythm and circulation, and the extent of injury to other organs and systems. Thus, physiologic variables such as rhythm, blood pressure, oxygenation, etc may be used to measure the value of interventions to reverse the conditions that lead to and perpetuate the arrest. However, in clinical practice, once survival is attained, physicians often face the need to establish the extent of neurological injury, particularly among those who do not recover consciousness. Although prognostication can be reliably established by 72 hours post arrest, one of its limitations is its value establishing the degree of neurological or cognitive impairment among those that do not have the findings associated with poor prognosis.4 More importantly, recent reports raise concerns about the effects of sedatives and hypothermia on the neurologic assessment of these patients and the need for extended periods of observation before reaching conclusions on prognosis.5
The consensus statement by Becker and the expert panel on primary outcomes for resuscitation science studies reflect the uncertainties still present in the field. A single primary outcome is certainly not appropriate for all studies and the choice of outcome depends on the question being asked.6 Even though endpoints could include restoration of rhythm or spontaneous circulation or reversal of myocardial ischemia, in the end all efforts do have a common goal: that of preserving neurological function. Interestingly, in the case scenarios analyzed during the panel’s deliberations, most experts agreed that a form of quality of life or neurocognitive measure was the most appropriate endpoint for most scenarios but more importantly they called for the development of an easy-to-administer validated neurologic scoring tool to use in all future resuscitation studies.4 At the present time it seems that: first, survival is not enough, and second, quality of life and neurological function do matter. Therefore, our task now is to answer the call and develop a reliable validated tool to assess neurological function in a standardized fashion.
- Roger VL, Go AS, Lloyd-Jones DM, et al. Heart disease and stroke statistics - 2011 update: a report from the American Heart Association. Circulation 2011;123(4):e18-e209.
- Berg RA, Hemphill R, Abella BS, et al. Part 5: adult basic life support: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation 2010;122[18 Suppl 3]:S685-705.
- Neumar RW, Barnhart JM, Berg RA, et al; on behalf of the American Heart Association Emergency Cardiovascular Care Committee, Council on Cardiopulmonary, Critical Care, Perioperative and Resuscitation, Council on Clinical Cardiology, Council on Epidemiology and Prevention, Council on Quality of Care and Outcomes Research, and Advocacy Coordinating Committee. Implementation strategies for improving survival after out-of-hospital cardiac arrest in the United States: consensus recommendations from the 2009 American Heart Association Cardiac Arrest Survival Summit. Circulation. 2011: published online before print May 16, 2011, 10.1161/CIR.0b013e31821d79f3.
- Wijdicks EF, Hijdra A, Young GB, Bassetti CL, Wiebe S. Practice parameter: Prediction of outcome in comatose survivors after cardiopulmonary resuscitation (an evidence-based review): Report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology. 2006;67:203-210
- Becker LB, Aufderheide TP, Geocadin RG, Callaway CW, et al; on behalf of the American Heart Association Emergency Cardiovascular Care Committee and the Council on Cardiopulmonary, Critical Care, Perioperative and Resuscitation. Primary Outcomes for Resuscitation Science Studies: A Consensus Statement from the American Heart Association
- Samaniego EA, Mlynash M, Caulfield AF, Eygorn I, Wijman CA. Sedation confounds outcome prediction in cardiac arrest survivors treated with hypothermia. Neurocrit Care 2011 15(1):113-9