Perioperative Lidocaine and Ketamine in 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