Evaluation of the Hemodynamic Effect of Intravenous Lidocaine on Propofol

1.INTRODUCTION General anesthesia can be dened as a drug-mediated reversible depression of the central nervous system resulting in the absence of response to and lack of perception of all external stimuli. The various components of anesthesia include unconsciousness, analgesia, amnesia, immobility, and suppression of autonomic responses to noxious stimulation.Consciousness is a complex state that can be divided into two components, namely, arousal and awareness, with both individually blocked by anesthetics. Awareness is the ability to process and store information that can be used to interact with internal or external environment. In contrast, arousal or wakefulness is the state of receptivity to the external environment and is likely mediated through subcortical structures such as the reticular activating system (RAS). An inadequate general anesthesia results in intraoperative awareness with or without recall and the consequent postoperative morbidity. Intraoperative electrophysiological monitoring using Bi Spectral Index (BIS) allows a reproducible, objective and continuous measurement of depth of anesthesia, even during the period when the patient is paralyzed and all reexes are abolished.[1] BIS monitor consists of a sensing electrode placed on the patient's forehead which reads out the patient's EEG in the form of a non-attributable number in the range of 0 to 100, by means of an integrated custom software. This value helps the anesthesiologist in assessing the conscious state of the patient and in modifying the dose of anesthetic drugs to maintain an adequate depth of anesthesia.[2] Systemic lidocaine infusion has been used in several studies to assess its benets on the outcome of anesthesia. Having inammation-modulatory properties, it signicantly reduced pain. Similarly, studies have shown that intravenous lidocaine infusion causes a decrease in the minimum alveolar concentration (MAC) of volatile anesthetic agents, thereby decreasing their requirement. There have been some studies postulating the reduction in intravenous anesthetic requirements by using lidocaine infusion.This study aims at evaluating hemodynamic changes of intravenous lidocaine in reducing requirements of propofol during general anesthesia as monitored by the Bi Spectral Index (BIS). The BIS index is maintained between 40 and 60 to maintain an adequate depth of anesthesia, and the anesthetic agents are titrated accordingly.