Inclusion Criteria:  at least 18 years of age having a unilateral video assisted thorascopic surgery who have preoperative placement of an erector spinae plane catheter.  Exclusion Criteria:  Known hepatic dysfunction or renal insufficiency (creatinine >1.5 mg/dL) allergy to the study medication pregnancy incarceration inability to communicate with the investigators morbid obesity (body mass index >40 mg/m2).