Lack of uniform definitions and reporting in laboratory models of cardiac arrest: A review of the literature and a proposal for guidelines+,++,*

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Background: Researchers are interested in improved uniformity of definitions and standards of reporting data for human CPR studies, and international guidelines (Utstein style) have been developed. However, no guidelines exist for animal CPR investigations.

Objective: To assess published animal CPR studies for adequacy of reporting and uniformity of methods and definitions regarding such important factors as the interval from the onset of ventricular fibrillation to the start of CPR (the nonintervention interval), ventilation, chest compression, coronary perfusion pressure, and return of spontaneous circulation.

Design: A blinded review of the methodology described in 42 articles concerned with animal CPR research published during the last ten years. An article had to report cardiac arrest and CPR as part of the protocol and return of spontaneous circulation as one of the outcome variables in order to be included in this study. We excluded abstracts, nonresuscitation models, and human CPR studies.

Measurements and main results: There was wide variation in the experimental methods reported in the studies. The nonintervention interval ranged from 0 to 15 minutes. The majority of studies initiated CPR within three minutes after the onset of ventricular fibrillation. Twenty-two percent of studies reported tidal volume, and 18% reported minute ventilation. Of the 14 studies that used blood pressure or coronary perfusion pressure as a target for titration of chest compression force, 12 used different target blood pressure values. We found 29 different definitions of return of spontaneous circulation. The duration of return of spontaneous circulation ranged from 30 seconds to 60 minutes; however, 52% of studies did not report a duration.

Conclusion: Important differences exist in animal CPR research methodology among laboratories. Failure to define or report minute ventilation, coronary perfusion pressure, and return of spontaneous circulation made it difficult to compare studies. In order to make valid comparisons of studies, blood flow and ventilation should be measured and controlled when they are not experimental variables. Uniform definitions and guidelines for reporting should be developed for laboratory CPR research.

Section snippets

INTRODUCTION

Modern CPR research has been heavily dependent on animal models that seek to simulate human cardiac arrest.1, 2 Animal models of cardiac arrest have been used to explore many important treatments, including epinephrine dose, chest compression techniques, and defibrillation energies.3 When favorable results are obtained in animal models, they often are implemented very soon afterward in human victims of cardiac arrest. Unfortunately, the favorable results obtained in one laboratory are often at

MATERIALS AND METHODS

To identify articles for inclusion, a literature search encompassing the period 1970 to 1992 was performed. More than 200 articles that reported on laboratory models simulating cardiac arrest were identified in peer-reviewed journals. Additional papers were identified from citations and collective reviews. From these papers, a set of criteria was developed for the paper to be included in the study: the report had to simulate cardiac arrest and CPR as part of the experimental protocol, and ROSC

RESULTS

Forty-two articles met the inclusion criteria. For each article, a variable was included in the present analysis only if it was the same in both the control group and the experimental group. This was done because one would not expect uniformity in a variable being tested experimentally. For example, in a study of the effect of different compression rates on ROSC, the study would not be included in the denominator of studies reporting compression rate but would be included in the assessment of

DISCUSSION

We found a wide range of experimental methods and reporting of information in these studies and an obvious lack of uniformity in definitions for critical variables. We believe that some guidelines would be useful to investigators. While there is no need for uniform research methods (in fact, this would inhibit experimental creativity), uniform definitions and terms and guidelines for data reporting would enhance CPR research (Figure 6).

. Guidelines for laboratory models of cardiac arrest

The

CONCLUSION

We reviewed several important aspects of animal models of cardiac arrest and saw a clear need for improvement in the uniformity of definitions and the establishment of guidelines for data reporting. Clearly such uniformity would improve our ability to interpret and compare the results of different laboratories. Obviously, not all animal studies should follow a uniform protocol. However, we believe that it would be possible to improve the uniformity and adequacy of reporting of animal studies

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    Presented in part at the Society for Academic Emergency Medicine Annual Meeting in San Francisco, May 1993, and the Emergency Medicine Research Society/Society for Academic Emergency Medicine Combined Meeting in Cambridge, England, September 1993.

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    This study was supported by Grant #91G1A/721 from the American Heart Association, Florida Affiliate, and a grant from the German Academic Exchange Service.

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    Reprint no. 47/1/51907 No reprints available from author

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