Dr. Thomassen’s group studied 20 patients who underwent primary total knee arthroplasty and received two intraoperative injections of ropivacaine. The researchers used intra-articular retransfusion drains and wound catheters for continuous infusion of 8 mg/hour of ropivacaine for 24 hours. Any blood collected through the retransfusion devices were used for laboratory analyses rather than being retransfused.
The team used the postoperative blood samples to predict cumulative ropivacaine concentrations and then constructed a model of instant retransfusion. The study found that retransfusion would result in an average of 13 mg of unbound ropivacaine being intravenously administered, meaning instant retransfusion could significantly increase unbound venous plasma concentrations. Local anesthetics combined with infusion of ropivacaine is potentially safe, but the process combined with shed blood transfusion could lead to toxic levels of the analgesic, according to the report.
Read the OrthoSuperSite report on retransfusion of shed blood.
Related Articles on Analgesia:
5 Recent Findings on Anesthesia in Children
Dr. Bruce Nicholson Presents Four Strategies to Tackle Post-Op Pain
Study: Increased Morphine Clearance in Sickle Cell Disease Patients
