Determination of moderate-to-severe postoperative pain on the numeric rating scale: a cut-off point analysis applying four different methods

Abstract

Cut-off points (CPs) of the numeric rating scale (NRS 0–10) are regularly used in postoperative pain treatment. However, there is insufficient evidence to identify the optimal CP between mild and moderate pain. A total of 435 patients undergoing general, trauma, or oral and maxillofacial surgery were studied. To determine the optimal CP for pain treatment, four approaches were used: first, patients estimated their tolerable postoperative pain intensity before operation; secondly, 24 h after surgery, they indicated if they would have preferred to receive more analgesics; thirdly, satisfaction with pain treatment was analysed, and fourthly, multivariate analysis was used to calculate the optimal CP for pain intensities in relation to pain-related interference with movement, breathing, sleep, and mood. The estimated tolerable postoperative pain before operation was median (range) NRS 4.0 (0–10). Patients who would have liked more analgesics reported significantly higher average pain since surgery [median NRS 5.0 (0–9)] compared with those without this request [NRS 3.0 (0–8)]. Patients satisfied with pain treatment reported an average pain intensity of median NRS 3.0 (0–8) compared with less satisfied patients with NRS 5.0 (2–9). Analysis of average postoperative pain in relation to pain-related interference with mood and activity indicated pain categories of NRS 0–2, mild; 3–4, moderate; and 5–10, severe pain. Three of the four methods identified a treatment threshold of average pain of NRS≥4. This was considered to identify patients with pain of moderate-to-severe intensity. This cut-off was indentified as the tolerable pain threshold.