Current Literature in EMS
Several reviewers have evaluated the quality and quantity of EMS research over the last 30 years. Figure 1 shows an appraisal of the number of EMS related manuscripts published each year since 1965. The data in the figure are the result of an extensive search of multiple National Library of Medicine (NLM) research databases including MEDLINE and CINAHL. Although the number of EMS publications is not vast, the volume has been increasing steadily over the years at a respectable rate. Since 1970, the quantity of published EMS literature increased at a rate of approximately 200 articles per decade. The increase is likely due to increased awareness of the need for study in this area and also the appearance of several new journals dedicated to the specialty. If this growth rate remains constant, about 900 articles will be published in the year 2010.
There have been many pleas to increase the number of clinical trials,56,57 and some have made eloquent points about the dangers inherent in the existence of so few methodologically sound studies.27 Concern for the lack of scientific support for many pre-hospital interventions, lack of uniform reporting methods, monitoring of outcomes and adverse effects invokes the need for reexamination of EMS practice.52,58,59
While randomized controlled trials may be the gold standard for clinical studies, they are not appropriate for every question. For example, randomized trials are not appropriate for studies of harm, prognosis, or diagnostic devices.60,61 Randomized controlled trials can also be more challenging to implement in systems and educational settings. Indeed, very little educational research utilizes randomized-controlled designs.62
Although the body of published EMS literature is growing steadily, there is much concern about the substance of the material. In a recent review of the EMS literature published between 1985 and 1994, the most frequently used study design was the case series, which accounted for 44 percent of the publications. The majority of EMS studies published during that ten-year period (53%) were retrospective in nature.59
Figure 2 shows the results of an analysis conducted for the National EMS Research Agenda project in which the NLM designated study type was used to classify the 9,232 identified EMS related citations published between 1966 and 2000. These categorizations are estimates, as not all studies included a design designation. Despite this limitation in the analysis, it remains apparent that the overwhelming majority of the published EMS literature is not research reports but rather historical articles, editorials, consensus development pieces, biographies, monographs, or guidelines.
Of those study types recognized as “research”, reviews (n=593; 6% of total) reigned over clinical trials (n=331; 4%) and meta-analyses (n=15; 0.1%). Evaluated on the basis of the strength of the study design, the majority of EMS studies published in peer-reviewed journals use unpersuasive methodology. The bulk of the published research can be characterized by its overwhelming propensity to use simple descriptive methods and retrospective techniques.
With the understanding that randomized clinical trials may not always be the most appropriate design for scientific validation of prehospital treatments or system changes, the number of randomized trials conducted has been used as a surrogate marker for the level of sophistication in research. With this limitation in mind, the proportion of randomized trials out of all the clinical investigations published in EMS has been reported to range between 1%27, 5%63and 15%.59 As a point of reference, the proportion of randomized trials published in the entire specialty of emergency medicine has not changed much over the years, increasing from 10% in 1983, to 12% in 1989, and reaching 15% by 1997.64 This proportion is thought to be similar to the proportion of randomized trials estimated to exist in published internal medicine literatures.65 Appendix F of this document lists published randomized or pseudo-randomized clinical trials conducted in the EMS setting from 1966 through 2000 that could be identified by the writing team.