Clinical studies have shown that IV administration of anesthetics, lidocaine and ketamine with their anti-inflammatory properties, modulates the acute immune response associated with surgical tissue injury, and in this manner they are able to reduce postoperative pain. Lidocaine has anti-inflammatory effects on polymorphonuclear granulocytes, IL-6 and IL-8 cytokines, complement component C3a and IL-1ra in serum. Ketamine produces its anti-inflammatory effects by reducing CRP and IL-6 in serum and by inhibiting NF-kB, which regulates gene transcription responsible for the production of proinflammatory factors.

Perioperative combinend IV administration of lidocaine and ketamine could have a more favorable anti-inflammatory effect compared to anesthetic given alone or with placebo.

To investigate the effects of lidocaine and ketamine in patients undergoing abdominal surgery on: acute immune response following the level of proinflammatory factors in serum (CRP, IL-6, IL-8); postoperative pain management; recovery of bowel function; administration of opioids; reduction of total treatment costs; length of hospital stay (LOHS)

A double-blind, placebo-controlled study will include 100 patients undergoing open colorectal surgery. Patients will be randomly assigned to one of four groups: lidocaine, ketamine, lidocaine-ketamine, and placebo. Lidocaine will be administered at a dose of 1.5 mg/kg prior to surgical incision followed by an infusion at a rate of 1.5-2 mg/kg/hr until the end of surgery. Ketamine will be administered at a dose of 0.5 mg/kg in a bolus prior to surgical incision followed by an infusion at a rate of 0.1-0.2 mg/kg/hr until the end of surgery. Bolus and continuous placebo infusion (0.9% NaCl) will be equally administered at the same dose as the aforementioned anesthetics until the end of the surgery.

Proinflammatory markers in serum (CRP, IL-6, IL-8) will be measured before induction of anesthesia, then 12 hours and 36 hours following the completion of surgery. The intensity of pain will be measured using the VAS score 2 hours and 4 hours following surgery and every 12 hours the following days. The investigators will measure also the consumption of opioids during and after surgery, the length of stay in the ICU, where pain control and analgesics use will be measured, as well as recovery of bowel function.

Inclusion Criteria:

• Elective Surgery
• Expected duration of the operation > 2 hours

Exclusion Criteria:

• Patients ≤ 18 years of age
• Patients with history of allergy to local anesthetics
• Chronic opioid analgesic
• Patients who are unwilling or unable to participate