Serum and Wound Drain Ropivacaine Concentrations After Wound Infiltration in Joint Arthroplasty

Ropivacaine blood and drain levels were measured in 20 hip and 15 total knee arthroplasties after intraoperative wound infiltration with 150 to 200 mL (360-400 mg) of ropivacaine, followed by a 48-hour intra-articular pain pump infusion of 1000 mg (knees) and 300 mg (hips) commencing 12 hours postoperatively. Concentrations were below 2 μg/mL over the first 12 hours before the pain pump increased levels. Peak total ropivacaine concentration ranged from 0.65 to 4.36 μg/mL with the pain pump. The high infiltration doses produced levels below or within the safe threshold of 1 to 3 μg/mL. Pain pump infusion produced some C_max levels above 3.0 μg/mL, but there was no clinical evidence of toxicity. Wound drain amounts (0.53-26.69 mg) indicate reinfusion should be safe, although further study is needed to confirm this.