67 y/o Pt for a TKR

Rx: metoprolol glucophage ASA

Surgeons at this facility been using Exparel and are finding that the exparel used alone isn't working until approx 4-6 hrs after injection, even if the surgeon uses Bupivacaine along with it. They don't want femoral blocks anymore because of the exparel.

The anesthetic for the procedure was as follows:

Sedation with Propofol gtt
Epidural running with Bupiv 0.125 @ 10cc/hr

Patient Seizure occurred 5 hours after Exparel injected and approx 10 min after the epidural was topped off with 5 cc of 1.5% Lido with Epi. Negative test dose. Epidural was going @ 10cc/hr.

What happened and why?