Lidocaine is a local anesthetic that is usually used for nerve blocks to sensory/motor blockade. However, lidocaine can also been given intravenously, and it has been shown that this method can be used to help alleviate chronic pain. We wish to investigate if lidocaine is infused via the transversus abdominis plane (TAP) block catheter will exert systemic effect, hence reduce opioid consumption and pain score in patients compared with using local anesthetic such as ropivacaine.

Following IRB approval and written consents, patients undergoing nephrectomy were randomized into 2 groups: standard 0.2% ropivacaine infusion (control) and 0.4% lidocaine infusion for TAP catheter. The TAP catheters were placed by the surgeons under direct vision at the end of surgery before wound closure. All subjects had a general anesthetic in accordance to the discretion of the anesthesiologist in the operating room. At the end of surgery, all patients received a patient-controlled analgesia (PCA) in recovery for 48 hours. The primary outcome was the total opioid consumption at the first 27 hours post-operatively. The secondary outcomes were the total opioid consumption at 4/12/24/36/48/60 hours after the initiation of local anesthetic infusion, the numerical rating scale (NRS) at rest and on movement at 4/12/24/36/48/60 hours after the initiation of the local anesthetic infusion, the incidence of nausea and vomiting, and adverse effects.

The sample size calculation for this non-inferiority trial is based on our previous retrospective study on TAP in nephrectomy patients. A sample of 80 patients is needed, using a power of 90% with the two-sided significance level of 5%. All parametric data will be analyzed using mean and standard deviation. Non-parametric data will be analyzed using median and interquartile range. Student's t-test or Mann-Whitney U test will be used to compare between groups.

Inclusion Criteria:

• Elective nephrectomy
• patients consent to study
• ASA I to III

Exclusion Criteria:

• Patient refusal
• Allergy to lidocaine,
• Patients with cardiac arrhythmias or on anti-arrhythmics or propranolol
• Wolf-Parkinson White syndrome
• Hepatic disease