Determination of clinically meaningful levels of pain reduction in patients experiencing acute postoperative pain.

Assessment is an essential, but challenging, component of any pain management plan. Nurses who care for postoperative patients quantify and document pain by use of unidimensional scales such as the numeric rating scale, the visual analogue scale, or a verbal descriptor scale. Improvements in pain ratings on these scales are viewed as a welcome result by nurses and doctors. Pain, however, is a multidimensional phenomenon. Furthermore, pain is subjective, and therefore no objective measure of pain exists that captures every aspect of the pain experience. Given that clinical decisions are made on the basis of existing scales, it is important to know how much reduction in pain is clinically meaningful from the patient's perspective. The aim of this study was to investigate this issue by comparing levels of postsurgical pain reduction measured by a numeric rating scale (NRS) with the patients' verbal descriptions of how meaningful they consider their pain reduction to be. A convenience sample of 150 postoperative patients was obtained. The patients' postoperative pain intensity levels before and after analgesia were measured and compared with their verbal descriptions of what constitutes a clinically meaningful pain reduction. The results of the study showed a significant correlation between the percentage of reduction in pain severity and the patients' descriptive ratings of pain improvement. A unique finding of the study was that the degree of incremental shift on an NRS of pretreatment and posttreatment pain levels is not a good predictor of clinical relevance from the patient's perspective. A more accurate predictor was found by converting the changes on the NRS to percentages. An important implication of this study is the need to include a scale in pain assessment instruments for assessing the level of clinical meaningfulness of pain reduction from the patient's perspective.