title: The addition of tramadol to morphine via patient-controlled analgesia does not lead to better post-operative pain relief after total knee arthroplasty.
abstract: BACKGROUND
  Tramadol is used as an analgesic in post-operative pain treatment. Intravenous tramadol is often combined with morphine to achieve better pain relief and less side-effects after orthopaedic surgery. However, the available evidence is insufficient to support this combination. For this reason, we conducted the present non-commercial, randomized, double-blind clinical trial.
  
  
  METHODS
  Sixty-three patients with osteoarthritis of the knee, selected for primary total knee arthroplasty (TKA), were randomized to receive saline or tramadol 100 mg/ml intravenously every 6 h during the first post-operative day (total, 400 mg/24 h). All patients had access to morphine via a patient-controlled analgesia (PCA) pump.
  
  
  RESULTS
  Neither during the 6 h after the first dose nor during the first post-operative day could we detect any statistically significant difference with regard to pain intensity, sedation and nausea between patients treated with tramadol and the placebo group. However, the withdrawal rate caused by insufficient pain relief was greater in the tramadol group (7/31) than in the saline group (2/32). This difference did not reach statistical significance. In the group of patients who remained in the study for 24 h ('per protocol'), those randomized to receive tramadol had a significantly (P < 0.05) lower morphine consumption (20 mg or 31%) than the placebo group.
  
  
  CONCLUSIONS
  Our study does not support the combination of tramadol and morphine via PCA for post-operative pain relief after primary TKA. In addition, our study indicates that morphine via PCA as the sole means of post-operative analgesia does not provide sufficient pain relief after TKA. Thus, other means of post-operative analgesia should be used following TKA.
authors.affiliation: Department of Medicine, Clinical Pharmacology, Stockholm, Sweden.
authors.forename: C-O
authors.initials: CO
authors.lastname: Stiller
authors.forename: H
authors.initials: H
authors.lastname: Lundblad
authors.forename: L
authors.initials: L
authors.lastname: Weidenhielm
authors.forename: T
authors.initials: T
authors.lastname: Tullberg
authors.forename: B
authors.initials: B
authors.lastname: Grantinger
authors.forename: P
authors.initials: P
authors.lastname: Lafolie
authors.forename: K-A
authors.initials: KA
authors.lastname: Jansson
mesh_terms: D000328:Adult; D000368:Aged; D000465:Algorithms; D016058:Analgesia, Patient-Controlled; D000701:Analgesics, Opioid / Q000008:administration & dosage*; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009020:Morphine / Q000008:administration & dosage*; D020370:Osteoarthritis, Knee / Q000601:surgery; D010147:Pain Measurement; D010149:Postoperative Pain / Q000188:drug therapy* / Q000209:etiology; D018709:Statistics, Nonparametric; D014147:Tramadol / Q000008:administration & dosage*; D016896:Treatment Outcome
chemical_list: D000701:Analgesics, Opioid; D014147:Tramadol; D009020:Morphine