HospitalÊre¯ter resuscitation from out of hospitalÊrdiac arrest The emperor's new clothes


Hospital care after resuscitation from out-of-hospital cardiac arrest: The emperor's new clothes?

PoczÄ…tek formularza

Dół formularza

PoczÄ…tek formularza

Dół formularza

Alfred Hospital, Baker Heart and Diabetes Institute, Melbourne, Australia

University of Washington-Harborview Center for Prehospital Emergency Care, Seattle, WA, United States

Received 29 March 2012 published online 16 April 2012.

  1. References

  2. Copyright

 

The large regional variation in outcome after treatment for out-of-hospital cardiac arrest (OHCA)1 has led to efforts to develop and implement cardiac resuscitation systems of care that include interconnected community, emergency medical services (EMS) and hospital efforts to measure and improve the process and outcome of care for this population.2 Implicit assumptions of these efforts are that care provided for patients with OHCA is better at some hospitals that receive such patients than others, and that resuscitated patients should be preferentially transported to higher-performing hospitals.

In this volume of Resuscitation, two investigations describe whether the characteristics of receiving hospitals are associated with outcome after OHCA. In a retrospective analysis that combined quality improvement data from the Cardiac Arrest Registry to Enhance Survival (CARES) registry with administrative information about hospital characteristics and hospitals' self-report of whether they use hypothermia to assess the relationship, Cudnik et al. evaluated whether increasing hospital volume of OHCA patients was associated with improved survival.3 They included adults who had OHCA of presumed cardiac etiology, were treated by EMS, and were directly transported to a hospital. The analysis used multi-level hierarchical logistic regression to adjust for the interaction between patient-level factors with hospital characteristics and the association between hospital characteristics within different sites. A significant relationship was observed between trauma center designation but not presence of a coronary catheterization laboratory or the volume of patients received and survival or neurologic outcome among all treated patients or those with a first-recorded shockable rhythm.

The hospital factor with the largest treatment effect in this study was self-reported use of hypothermia. Since only a minority of patients have hypothermia induced at hospitals that report that they use it,4 reported use of hypothermia may be a surrogate marker for other factors that are associated with outcome, and attenuate the effect of hospital factors upon patient survival to discharge.

This study restricted enrollment to patients with a cardiac etiology of arrest. There is a twofold variation in the reported proportion of cardiac arrests of non-cardiac etiology.5 There is poor agreement in attributing cause of heart failure deaths.6Information from 12-lead electrocardiogram does not identify which patients among those resuscitated from OHCA have significant lesions at time of emergency catheterization.7 Assessment of the etiology of arrest is difficult to assess accurately in field. If etiology is determined using hospital information, assessing etiology is conditioned on survival to hospital, and analyses restricted to cardiac etiology of arrest are susceptible to bias. Thus the revised Utstein approach to comparing outcomes after OHCA recommended including all treated patients rather than those with a particular etiology or initial rhythm.8

In another retrospective analysis published simultaneously as the CARES work, Ro et al. evaluated the relationship between the annual volume of patients received at hospitals and survival to discharge after cardiac arrest of non-cardiac etiology in a national Korean registry derived from combination of ambulance run sheets with hospital data abstracted by trained reviewers.9 Generalized additive modeling evaluated for a threshold value that discriminated between a low and high volume of patients received. Then multiple logistic regression analysis evaluated whether there was an association between the volume of patients received and survival to discharge. There was a significant and important difference in survival to discharge among patients transported to a high volume hospital rather than low volume hospital overall and within specific etiologies of arrest.

There are several potential explanations why an association between patient volume and outcome was not observed in the CARES registry but was in the Korean registry. The quality of care may be lower among CARES hospitals than among Korean hospitals, but this seems unlikely since overall survival was greater in the former than in the latter. The accuracy of the data in each registry may differ as CARES performs limited data verification at the source whereas staff of the Korean registry visit participating hospitals and review medical records to identify information related to covariate and outcome. It seems plausible that bias and confounding in CARES data may reduce the likelihood of identifying whether differences in care are associated with differences in survival.

Prior studies provide conflicting evidence regarding the influence of hospital factors on survival after OHCA. A Japanese study that included more 10,000 patients showed that OHCA patients transported to critical cardiac care hospitals had improved 1-month survival compared with patients transported to hospitals without specialized facilities (6.7% versus 2.8%,p0x01 graphic
<0x01 graphic
0.001, adjusted odds ratio 3.39, p0x01 graphic
<0x01 graphic
0.001).10 A Swedish study of almost 4000 OHCA patients reported marked variability in hospital outcomes after adjusting for pre-hospital factors, with survival varying from 14% to 42% in different centres.11 Similarly a recent Australian study of 2706 patients who were transported to hospital with return of a spontaneous circulation found that survival to hospital discharge was significantly greater in patients transported to hospitals with 240x01 graphic
h interventional cardiology facilities, with the best survival in major trauma-level hospitals.12 A US study of 109,739 patients who received intensive care in hospital indicated that hospital teaching status, size and urban location were associated with outcome in patients resuscitated from in-hospital and out-of-hospital cardiac arrest.13

Conversely, a North American study of 4087 patients with OHCA reported increased rates of survival among patients resuscitated from OHCA who were treated at larger hospitals capable of invasive cardiac procedures but this effect was not independent of pre-hospital factors.14

How should variation in outcome after hospitalization for post-resuscitation care be interpreted in the context of factors associated with variations in outcomes of other conditions? Variation in outcomes after hospitalization for acute myocardial infraction has been associated with hospitals' teaching status,15 urban location,16 geographic region,17 safety net status,18and institutional culture.19 Additional work is necessary to understand and improve the variation in process and outcome after OHCA as has been done for acute myocardial infarction.

There are multiple examples throughout the field of medicine of the positive correlation between greater provider experience or procedural volume for complex diagnoses or procedures and better patient outcome.20 The relationship between volume and outcome is complex. Procedural volume is an identifiable surrogate marker for a number of patient, physician, and systems variables that have an impact on outcome but are difficult to quantify individually.

Despite inconsistent evidence of a relationship between the volume of patients a hospital receives after cardiac arrest and their subsequent survival, we believe that it would be premature to conclude that implementation of regional cardiac resuscitation systems of care will not improve process and outcome. We recommend that future efforts to evaluate the effect of regionalization in this population should include all patients regardless of the putative etiology of their arrest, and should be consistent with the Utstein approach. Until such an evaluation has been completed, it seems reasonable to preferentially transport patients who have been resuscitated from OHCA to a facility with trauma center designation and other facilities to enable use goal-directed therapies including therapeutic hypothermia, primary percutaneous coronary intervention, together with comprehensive neurological assessment and therapy regardless of the volume of patients with OHCA that the hospital receives annually. Indeed, the emperor is wearing clothes.

References 

  1. Nichol G, Thomas E, Callaway CW, et al. Regional variation in out-of-hospital cardiac arrest incidence and outcome. JAMA.2008;300:1423-1431

  • Nichol G, Aufderheide TP, Eigel B, et al. Regional systems of care for out-of-hospital cardiac arrest: a policy statement from the American Heart Association. Circulation. 2010;121:709-729