Rebound pain following peripheral nerve block anaesthesia in acute ankle fracture surgery: An exploratory pilot study

BACKGROUND: Peripheral nerve blocks (PNB) are increasingly used for anaesthesia and postoperative pain control in acute orthopaedic limb surgery but rebound pain upon cessation of PNBs may challenge the benefits on the pain profile. We aimed to explore the pain profile following acute ankle fracture surgery under PNB anaesthesia and investigate if rebound pain could pose a clinical problem. METHODS: Exploratory, observational study of adults scheduled for acute primary internal fixation of an ankle fracture under ultrasound-guided popliteal sciatic and saphenous ropivacaine block anaesthesia. Postoperatively, patients regularly registered pain scores while receiving a fixed analgesics regimen and patient controlled morphine on-demand. We analysed morphine consumption and depicted the detailed pain profiles as graphs allowing for visual analysis of pain courses, including rebound pain. Secondly, we compared the area under the curve and peak pain between relevant age-subgroups. RESULTS: We included 21 patients aged 20-83. Depicted pain profiles reveal that PNB supplied effective and long lasting postoperative pain control, but cessation of the PNB led to intense rises in pain scores with six out of nine 20-60-year-olds reaching severe pain levels. The rebound was less pronounced in patients >60 years old, but nearly all reached moderate pain levels. Morphine consumption rates were high during the rebound. CONCLUSIONS: This study thoroughly analyses the post-PNB pain profile and suggests rebound pain is a clinically relevant and problematic issue with the potential to outweigh the PNB benefits, especially for younger patients. The conclusions are tentative, and a randomised study is pending.