Serum levels of bupivacaine over time after peri-articular injection of a mixture of liposomal bupivacaine and plain bupivacaine during total knee arthroplasty.

Inclusion Criteria:

• Adults of at least 18 years of age having a primary, unilateral total knee arthroplasty with a surgical plan to have an intra-articular injection of a mixture of 266 mg of Exparel, 125 mg of bupivacaine, 1:300,000 epinephrine, and 0.9% saline to make a total volume of 100 ml.

Exclusion Criteria:

• Known hepatic dysfunction or renal insufficiency (creatinine > 1.5 mg/dL);
• allergy to the study medications;
• pregnancy;
• incarceration;
• inability to communicate with the investigators;
• morbid obesity (body mass index > 40 kg/m2).

Adults of at least 18 years of age having a primary, unilateral total knee arthroplasty with a surgical plan to have an intra-articular injection of a mixture of 266 mg of Exparel, 125 mg of bupivacaine, 1:300,000 epinephrine, and 0.9% saline to make a total volume of 100 ml.