Time Effect on Acute Postoperative Pain After Total Knee Replacement Surgery: An Exploratory Study Using the Experience Sampling Method

OBJECTIVES: Acute postoperative pain (APP) is the main cause of postoperative dissatisfaction; however, traditional methods of pain assessment provide limited insights into the dynamics and development of APP. This study used the experience sampling method (ESM) to understand the dynamics of APP over time in relation to various patient factors. METHODS: Forty patients scheduled to undergo total knee replacement surgery were recruited in this study. Following an initial assessment, a short report questionnaire was sent to the patients via 10 digital alerts per day to assess the pain levels during two preoperative and the first 6 postoperative days. The data were analyzed using multilevel regression including random intercept and slope. RESULTS: Thirty-two patients submitted the pre-specified minimum of 30% of their short reports, yielding 1217 records. The analysis revealed significant (P<0.001) linear and quadratic decreases in APP and a quadratic time effect. The lowest between-days and within-day pain levels were observed on postoperative day 4.8 and during the time slot 3.8 or approximately 19:15, respectively. Significant random intercepts and slopes were noted, indicating variations in the mean pain level between patients and a decrease in pain. None of the 10 patient factors had any confounding effect. DISCUSSION: Using ESM data combined with multilevel analysis, we were able to evaluate the postoperative pain course while considering inter-individual differences in the baseline pain level and non-linear pain course over time. The findings of this study could aid clinicians in personalizing the treatment for APP.