Perioperative Lidocaine and Ketamine in Abdominal Surgery

The investigators propose to test the hypothesis that perioperative infusions of lidocaine and/or ketamine reduce opioid consumption and pain scores in adults recovering from elective inpatient abdominal surgery.

Inclusion Criteria: * Adults 18 to 80 years old * Elective inpatient open or laparoscopic abdominal surgery * General anesthesia lasting 2 hours or longer. Exclusion Criteria: * 1\. Planned postoperative mechanical ventilation * 2\. Planned regional anesthesia/analgesia * 3\. Perioperative gabapentin, magnesium, or nitrous oxide use * 4\. Pregnancy or breastfeeding * 5\. Morbid obesity (BMI ≥ 35 kg/m2) * 6\. American Society of Anesthesiologists (ASA) physical status IV-V * 7\. Allergy to study medications * 8\. Contraindication to lidocaine (severe cardiac arrhythmia) * 9\. Contraindication to ketamine (psychiatric disorder, substance abuse, uncontrolled hypertension, pulmonary hypertension, increased intracranial or intraocular pressure, use of monoamine oxidase inhibitors) * 10\. Chronic preoperative opioid use (≥ 90 morphine mg equivalents per day for \> 3 months) * 11\. Significant preoperative hepatic dysfunction (alanine aminotransferase or aspartate aminotransferase levels \> 5 times normal) or planned liver transplantation * 12\. Preoperative cardiac failure (left ventricular ejection fraction ≤ 40%) * 13\. Unable to communicate or comprehend study instructions