The Goal of "no Worse Than Mild Pain" in Daily Clinical Practice: Individual Responder Analysis - a Cross-sectional Prospective Cohort Study of Surgical Patients at Zealand University Hospital, Koege

In contemporary postoperative pain management, patients are treated with combinations of non-opioid and opioid analgesics, and analgesic methods. The intention is to enhance pain relief from additive or synergistic effects of such combinations. However, the literature is complex and heterogenic and characterized by small sized studies investigating a diversity of analgesic combinations and methods. Consequently no well-documented "best current proven intervention" is definable

Efficacy of analgesics is most often based on results from randomized trials measuring differences between two groups based on the average pain level in each group, for example median or mean. This approach has weaknesses as individual patients vary in response, and the average pain level is actually only experienced by few patients. Also, it is well known that analgesics may only work in 30- 50% of the patients and it is not possible to predict who will experience excessive pain. Besides, data on pain score does not follow a normal distribution, but usually is either very good or very bad. Studies have demonstrated, that basically, patients want efficient pain treatment with large pain reductions (for example 50%) and/or pain levels corresponding to mild pain, Numeric Rating Scale ≤ 3. Pain treatment that does not include the achievement of adequate pain relief are likely to fail.

Consequently, a new and simple universal criterion for postoperative analgesic success has been suggested based on individual patient response analyses: Efficacy should be measured on the individual level, and patients should experience "no worse than mild pain"(Numeric Rating Scale ≤ 3). In a re-calculation of individual patient data from 16 randomized clinical trials, the investigators have recently documented that by using the success criteria that at least 80% of patients should achieve Visual Analogue Scale ≤ 30, only about 50% of the studies had achieved goal fulfillment.

A current review has further documented, that movement evoked pain is underreported. Only 39% of trials measured movement evoked pain even though trials measuring both movement evoked pain and pain at rest suggest that movement evoked pain is 95% - 226% more severe and intense for the patient than pain at rest. Therefore it is of great importance for the benefits and treatment of patients, that future trials not only record pain at rest but also movement evoked pain, and additionally supply relevant information about the actual physical maneuver used for assessment.

It is therefore essential, in the light of "no worse than mild pain", and based on individual responder analysis, to investigate current benefit and harm of postoperative pain treatment. Our goal is to highlight the need for an intensified focus on individual patient's pain and the investigators expect to shed a new and critical light on current clinical pain treatment.