Comparing Post-Op Narcotic Usage in Patients Receiving Periarticular Exparel vs. Standard Periarticular Joint Inj

Opioids have been prescribed with increasing frequency for non-acute, non-cancer pain in the last 15 years. Because of this, opioid tolerance in the general population has grown markedly, and opioid tolerant patients can be especially difficult to manage in the perioperative period. In general, they require much higher doses of opioids to obtain similar levels of pain-control compared to opioid-naïve patients and are susceptible to respiratory depression and other adverse events. This study seeks to determine whether a new sustained-release local anesthetic solution (Exparel - Liposomal Bupivacaine) injected into the soft tissues around the joint after surgery will decrease opioid consumption and adverse events in opioid-tolerant patients presenting for total knee arthroplasty.

Inclusion criteria

• Males and Females age 18+ years old having total knee arthroplasty at UCI
• Meet at least one of the following criteria "opioid tolerant":
• Taking 50mg oral morphine equivalent or more per day
• On long-acting opioids (fentanyl pathc, oxycontin, methadone, etc.)
• Being followed by a chronic pain physician
• All subjects must be free of renal or hepatic dysfunction; defined as:
• Glomerular filtration rate >60 mL/min/1.73m^2
• AST & ALT <150, total bilirubin <1.0, INR <1.3 (if not taking anticoagulants)
• No active hepatitis, no jaundice

Control group- received standard periarticular injection Research group- receives Exparel injection

Exclusion criteria

• Allergy to local Anesthetic
• Pregnancy
• Nursing mothers
• Children<18 years of age
• Renal impairment (GFR<60 mL/min/1.73 m^2
• Hepatic impairment (active hepatitis, elevated AST or ALT, jaundice)
• Any history of ventricular arrhythmia or supraventricular tachycardia, or myocardial infarction within the last six months.