Postoperative pain management after total hip arthroplasty. A focus on evidence, clinical practice and the individual patient’s pain response

Abstract: Background: Patients experiencing high levels of pain after surgery remains a considerable clinical problem. Often, no consensus about the best analgesic treatment is present. The majority of clinical trials regarding postoperative pain, generally, target the average analgesic efficacy. In terms to step forward, a focus on the individual patients´ pain levels is needed and an identification of the patients in risk of developing higher postoperative pain levels.Aim: The overall aim was to explore the pain management for total hip arthroplasty (THA) patients by investigating the evidence in the literature, and the manifestation in clinical practice, including a focus on the individual patient and possible predictive tools.Methods: A systematic review was conducted investigating the different analgesic treatments in randomised clinical trials (RCT) regarding THA patients (Study I). To investigate the analgesic efficacy at the individual patient level, in terms of obtaining, ‘no worse than mild pain / VAS ≤30, a re-analysis was performed which included individual patient data of previous RCTs (Study II). The effect of multimodal analgesic treatment in THA patients in clinical practice was mapped in a large multicenter cohort study at five different hospitals (Study III). Finally, we investigated if four different and simple approaches were able to predict high levels of pain postoperatively: pain during peripheral venous cannulation (PVC), highest pain levels at the Post Anaesthesia Care Unit (PACU), PACU nurses prediction, and patient’s forecast. (Study IV).Results: In the systematic review, we found that the literature regarding the analgesic treatment for THA was heterogeneous and with no “gold standard”. The re-analysis demonstrated, based on the success criteria 80% should obtain VAS-pain ≤30, at 6 and 24hr postoperatively, half of the patients succeeded reaching the goal at rest. During mobilisation only 14-15% obtained the goal. The multicenter study demonstrated large differences in the analgesic treatment between hospitals. Surprisingly, did the patients´ pain levels not differ much, no matter which kind of analgesic treatment they had received, neither at a hospital-level nor at an individual patient level.None of the four predictive tools showed efficacy in predicting high pain responders at 24hr postoperatively during mobilisation.Conclusions: The literature regarding analgesic treatment for THA is heterogenic with no “gold standard.” When re-analysing 16 previous RCTs we found insufficient pain treatment at the individual patient level, especially during mobilisation. The pain treatment for THA at five different hospitals differed a lot. No matter how complex the multimodal pain was, patients´ outcomes were very similar according to pain and side effects. PVC-pain preoperatively could not be used as a predictive tool for patients with high pain levels after 24hr during mobilisation postoperatively. That was also the findings with PACU nurses prediction, highest pain levels at the PACU and patients forecast