Participants with mild, moderate, or severe pain following total hip arthroplasty. A sub-study of the PANSAID trial on paracetamol and ibuprofen for postoperative pain treatment

Abstract

Abstract Objectives In this sub-study of the ‘Paracetamol and Ibuprofen in Combination’ (PANSAID) trial, in which participants were randomised to one of four different non-opioids analgesic regimen consisting of paracetamol, ibuprofen, or a combination of the two after planned primary total hip arthroplasty, our aims were to investigate the distribution of participants’ pain (mild, moderate or severe), integrate opioid use and pain to a single score (Silverman Integrated Approach (SIA)-score), and identify preoperative risk factors for severe pain. Methods We calculated the proportions of participants with mild (VAS 0–30 mm), moderate (VAS 31–60 mm) or severe (VAS 61–100 mm) pain and the SIA-scores (a sum of rank-based percentage differences from the mean rank in pain scores and opioid use, ranging from −200 to 200%). Using logistic regression with backwards elimination, we investigated the association between severe pain and easily obtainable preoperative patient characteristics. Results Among 556 participants from the modified intention-to-treat population, 33% (95% CI: 26–42) (Group Paracetamol + Ibuprofen (PCM + IBU)), 28% (95% CI: 21–37) (Group Paracetamol (PCM)), 23% (95% CI: 17–31) (Group Ibuprofen (IBU)), and 19% (95% CI: 13–27) (Group Half Strength-Paracetamol + Ibuprofen (HS-PCM + IBU)) experienced mild pain 6 h postoperatively during mobilisation. Median SIA-scores during mobilisation were: Group PCM + IBU: −48% (IQR: −112 to 31), Group PCM: 40% (IQR: −31 to 97), Group IBU: −5% (IQR: −57 to 67), and Group HS-PCM + IBU: 6% (IQR: −70 to 74) (overall difference: p=0.0001). Use of analgesics before surgery was the only covariate associated with severe pain (non-opioid: OR 0.50, 95% CI: 0.29–0.82, weak opioid 0.56, 95% CI: 0.28–1.16, reference no analgesics before surgery, p=0.02). Conclusions Only one third of participants using paracetamol and ibuprofen experienced mild pain after total hip arthroplasty and even fewer experienced mild pain using each drug alone as basic non-opioid analgesic treatment. We were not able, in any clinically relevant way, to predict severe postoperative pain. A more extensive postoperative pain regimen than paracetamol, ibuprofen and opioids may be needed for a large proportion of patients having total hip arthroplasty. SIA-scores integrate pain scores and opioid use for the individual patient and may add valuable information in acute pain research.