Pharmacokinetics of Lidocaine Infusion: Optimal Dosing and Duration in ERAS Protocol

The Enhanced Recovery After Surgery (ERAS) protocol promotes multimodal analgesia to optimize postoperative pain control and reduce opioid consumption. To mitigate the risks of opioid-induced respiratory depression and postoperative ileus, ERAS incorporates alternative strategies, including continuous lidocaine infusion. However, excessive administration of lidocaine can cause local anesthetic systemic toxicity (LAST), potentially leading to adverse central nervous system and cardiovascular effects such as respiratory depression, seizures, coma, arrhythmia, and cardiac arrest. This study aims to develop a pharmacokinetic model of lidocaine infusion using a one-compartment approach based on differential equations. Assuming a half-life of 2 hours and a maximum safe plasma concentration of 5 mg/kg, the model predicts lidocaine concentrations over time, estimates the optimal discontinuation point, and calculates the additional allowable bupivacaine dose for a transversus abdominis plane (TAP) block at the end of surgery to minimize the risk of LAST.