64-year-old male, diabetic and hypertensive. He had severe chronic kidney disease (stage 5 with GFR 11 ml/min/1.73 m2). Scheduled for total right hip arthroplasty due to severe coxarthrosis. He underwent haemodialysis the day before the operation, his "dry" weight being 69 kg. At 9:20 a.m. we performed spinal anaesthesia with a 25 G sprotte needle (Pajunk®) with 2.5ml of bupivacaine 0.5% (12.5 mg) obtaining a complete block without incident. At 10:00 a.m. a 25 µg/h fentanyl patch (transdermal therapeutic system -TTS) is applied. The operation was uneventful. On arrival at the post-anaesthesia recovery unit (PRU) (12:30 a.m.) a perfusion of 6 grams of metamizole over 24 hours (in 500 ml of saline at a rate of 21 ml/hour) is started. The patient is admitted to the postoperative acute pain unit (PACU) maintaining the fentanyl patch for 48 hours and rescuing the pain with 200 µg transmucosal oral fentanyl (maximum every 4 hours with a maximum of 4 doses per day). At 16:00 she was discharged to the ward with a score of 2 on the visual analogue scale (VAS). At 22:00, due to a pain peak, a dose of oral transmucosal fentanyl is administered; it subsides after 15 minutes. At 12 hours after removal of the patch (60 hours after the operation) another pain peak appeared, requiring a second oral fentanyl. The VAS on the 2nd and 3rd days was 0. It was on the third day, coinciding with the change from bed to armchair, that the patient reported nausea which subsided with ondansetron 4 mg i.v. During his stay in the care of the ADU he had no vomiting, pruritus or constipation; the quality of sleep and night's rest were good.