title: Is peri-articular multimodal drug infiltration in knee arthroplasty safe when used in conjunction with autologous retransfusion drains?
abstract: BACKGROUND
  Adequate peri-operative analgesia following total knee arthroplasty (TKA) promotes earlier rehabilitation but remains problematic because of the drug side-effects. Peri-articular multimodal drug infiltration (PMDI) has been developed as an alternative strategy to avoid such complications. Autologous retransfusion drains reduce the need for peri-operative allogenic blood transfusions and the consequent risk. There is a theoretical risk of local anaesthesia toxicity when these systems are used concurrently. We performed a review of current practice to quantify this risk.
  
  
  METHODS
  A series of 10 patients undergoing TKA by the senior author (CAB) had drain fluid analysed for the concentration of ropivacaine. At the same time, the patients completed a questionnaire to establish the presence of ropivacaine-induced side-effects.
  
  
  RESULTS
  The ropivacaine level in the retransfusion blood was less than 10 mg in all patients. This concentration was a factor of 6 below the published safe level. Three patients had minor neurological disturbances which recovered spontaneously and quickly. There were no cases of significant cardiovascular compromise.
  
  
  CONCLUSIONS
  The theoretical risk of local anaesthesia toxicity when these systems are used together is negligible and we conclude that peri-articular multimodal drug infiltration is safe in conjunction with the use of autotransfusion drains.
authors.affiliation: Trauma and Orthopaedic Department, Ashford & St Peters NHS Trust, Ashford, UK. ian.gill@bsuh.nhs.uk
authors.forename: I
authors.initials: I
authors.lastname: Gill
authors.forename: K
authors.initials: K
authors.lastname: Gallagher
authors.forename: C A
authors.initials: CA
authors.lastname: Busch
mesh_terms: D000577:Amides / Q000008:administration & dosage / Q000009:adverse effects* / Q000097:blood; D000779:Anesthetics, Local / Q000008:administration & dosage / Q000009:adverse effects* / Q000097:blood; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001804:Blood Transfusion, Autologous; D002493:Central Nervous System Diseases / Q000139:chemically induced; D004305:Dose-Response Relationship, Drug; D004322:Drainage / Q000379:methods; D006801:Humans; D007270:Injections, Intra-Articular; D010149:Postoperative Pain / Q000517:prevention & control; D018570:Risk Assessment / Q000379:methods; D000077212:Ropivacaine
chemical_list: D000577:Amides; D000779:Anesthetics, Local; D000077212:Ropivacaine