Emergency Medical Services/Concepts
Emergency Medical Services Outcomes Project (EMSOP) IV: Pain measurement in out-of-hospital outcomes research*,**,*

https://doi.org/10.1067/mem.2002.124756Get rights and content

Abstract

The purpose of the Emergency Medical Services Outcomes Project (EMSOP) is to develop a foundation and framework for out-of-hospital outcomes research. In prior work (EMSOP I), discomfort had the highest weighted score among outcome categories for the top 3 adult conditions (ie, minor trauma, respiratory distress, chest pain) and the first and third highest rankings for children's conditions (ie, minor trauma, respiratory distress). In this fourth article in the EMSOP series, we discuss issues relevant to the measurement of pain in the out-of-hospital setting, recommended pain measures that require evaluation, and implications for outcomes research focusing on pain. For adults, adolescents, and older children, 2 verbal pain-rating scales are recommended for out-of-hospital evaluation: (1) the Adjective Response Scale, which includes the responses “none,” “slight,” “moderate,” “severe,” and “agonizing,” and (2) the Numeric Response Scale, which includes responses from 0 (no pain) to 100 (worst pain imaginable). The Oucher Scale, combining a visual analog scale with pictures, seems most promising for out-of-hospital use among younger children. Future research in out-of-hospital care should be conducted to determine the utility and feasibility of these measures, as well as the effectiveness of interventions for pain relief. [Maio RF, Garrison HG, Spaite DW, Desmond JS, Gregor MA, Stiell IG, Cayten CG, Chew JL Jr, MacKenzie EJ, Miller DR, O'Malley PJ. Emergency Medical Services Outcomes Project (EMSOP) IV: pain measurement in out-of-hospital outcomes research. Ann Emerg Med. August 2002;40:172-179.]

Introduction

This is the fourth article in a series reporting the results of the Emergency Medical Services Outcomes Project (EMSOP), a 5-year effort sponsored by the National Highway Traffic Safety Administration. The objective of EMSOP is to develop a foundation and framework for out-of-hospital outcomes research. Fundamental to that purpose is the identification of priority conditions, risk-adjustment measures, and outcome measures. Previous article topics included the results of a systematic process to determine priority emergency medical services (EMS) research conditions,1 the presentation of a conceptual framework for risk adjustment and outcomes measurement in out-of-hospital research,2 and suggested core risk-adjustment measures that will be useful for future EMS outcomes research.3 In this article, we will discuss a number of issues relevant to researching pain as an outcome measure in the out-of-hospital setting: (1) measurement of pain, (2) suggestions for the evaluation of pain measurements, and (3) implications for future research.

In EMSOP I, an expert panel identified relief of discomfort as the most relevant outcome parameter in both the adult and pediatric priority conditions1 and the out-of-hospital intervention that might have the greatest effect on patients. These findings are consistent with the opinion of one noted EMS investigator4 who suggests that relieving discomfort might be the most important task EMS providers perform for the majority of their patients. Although acknowledging the importance of survival as an outcome parameter, the principal recommendation of EMSOP I was that relief of discomfort should be a major area for out-of-hospital outcomes research.1 Among adults, the panel identified relief of discomfort as providing the greatest potential benefit for the priority conditions of minor trauma, respiratory distress, and chest pain. Among children, the panel identified relief of discomfort as providing the greatest potential benefit for the priority conditions of minor trauma and respiratory distress.1

For minor trauma and chest pain, the parameter of discomfort is pain. In fact, pain is one of the most common chief complaints among individuals seeking medical care. Furthermore, adverse effects of acute pain are associated with significant morbidity and mortality.5, 6, 7, 8, 9, 10, 11, 12 Despite the importance of the problem, medical care providers have not adequately addressed pain control.13, 14, 15 In the field of emergency medicine, inadequate pain control is also recognized as an important issue, both in the emergency department and in the out-of-hospital setting.16, 17, 18, 19, 20, 21 It has been suggested that this gap in the management of pain is primarily caused by the inadequate application of available knowledge and therapies and the lack of information on certain aspects of acute pain resulting from insufficient research.22 As a result of the importance of relieving discomfort and, specifically, pain, the EMSOP investigators have devoted an entire article to the challenges of measuring pain in the out-of-hospital setting.

To identify pain measures that have the most promise for out-of-hospital use, we conducted a MEDLINE search of English-language articles from 1966 to 2000 using the Ovid search engine. We identified articles addressing the measurement of pain or the comparison of pain measurement instruments. We reviewed appropriate articles and completed a hand search of the references from those articles to include references that were non–English-language articles. A hand search of government publications was also completed. The EMSOP investigators prepared a summary of the literature review.

EMSOP investigators and consultants then met to discuss the summary and make recommendations. In identifying pain measures that have the most promise for out-of-hospital use, EMSOP investigators and consultants made recommendations using the following criteria: (1) the measure has characteristics that imply it can be easily used in the out-of-hospital setting, (2) the instruments have been successfully used in other health care settings, and (3) the instruments were agreed on by all EMSOP investigators and consultants.

Section snippets

Measuring pain

According to the Agency for Healthcare Research and Quality, patient self-report is the most reliable indicator of the existence and intensity of pain.13 A tool for pain measurement should identify the presence of pain and the change of pain over time and allow for ease of use by an individual, regardless of psychologic, emotional, or cultural background. Furthermore, in the emergency setting, it is important to use a method of measurement that requires a relatively short period of time and is

The challenge: Application of pain measures in the out-of-hospital setting

Only 2 previous studies evaluated different pain measures in the out-of-hospital setting. One study56 evaluated the use of a 0- to 4-point verbal response scale (0, no pain; 4, extremely intense pain) and a 10-cm VAS in the out-of-hospital setting. Thirty-five percent of patients were not evaluated as a result of altered level of consciousness (85%) or emotional, psychiatric, or language difficulties. Another study found that among out-of-hospital patients reporting pain with the ARS, 26%

Pain measures recommended for evaluation in the out-of-hospital setting

In identifying pain measures to recommend for evaluation in the out-of-hospital setting, we considered ease of use in the out-of-hospital setting and successful use in other health care settings. Specifically, we sought to identify measures that could be used on a daily basis by out-of-hospital care providers and not just by EMS researchers. Although data are limited, the findings consistently show that, compared with the ARS and the NRS, patients receiving emergency care complete the VAS less

Future research

The paucity of pain research in the out-of-hospital setting underscores the need for descriptive and methodologic studies for developing and evaluating strategies to safely minimize pain. The following are needed: (1) studies to substantiate or refute the appropriateness of the pain measures suggested by the EMSOP investigators; (2) studies to determine the feasibility and reliability of using a verbal rating scale among all levels of out-of-hospital care providers; and (3) studies to determine

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    Authors' affiliations are provided at the end of this article.

    **

    Supported by the US Department of Transportation, National Highway Traffic Safety Administration (Cooperative Agreement No. DTNH22-96-H-05245).

    *

    Address for reprints: Ronald F. Maio, DO, MS, Department of Emergency Medicine, University of Michigan, 300 N. Ingalls Building, Room 2D06, Ann Arbor, MI 48109-0437; 734-936-1724, fax 734-936-2706; E-mail [email protected]

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