Sudar Codi Ramarajan
Abstract
Propofol is an intravenous anesthetic agent used since 1980s for the induction and maintenance of anesthesia in day care surgery. It has the unique property of rapid induction with rapid and complete recovery from general anesthesia. Propofol undergoes multicompartmental pharmacokinetics. Hence, continuous measurement of  plasma concentration of propofol (Cp) throughout the surgical procedure is a difficult task. Several manual infusion regimens were put forth to optimize the dose requirement and ensure rapid emergence. However, their use was limited by the inaccurate prediction of propofol plasma concentration which was overcome by Marsh et al. They used a three‑compartment pharmacokinetic model in comparison to other models with minimal prediction errors. Preprogrammed computerized target‑controlled infusion (TCI) device combines a pharmacokinetic model with an infusion pump and helps an anesthesiologist to titrate target blood propofol concentrations according to the requirement. Diprifusor is a standard computerized TCI device which incorporates the Marsh pharmacokinetic model with an infusion pump and helps to adjust the target plasma propofol concentration or the effect site propofol concentration. Cpcalc of propofol is the predicted plasma concentration of propofol, calculated based on the formula employed in the TCI pumps that incorporates various pharmacokinetic variables such as volume of distribution, clearance, and nonpharmacokinetic variables, namely age, weight, etc., Nonpharmacokinetic factors such as gender and ethnicity do alter the Cpcalc of propofol, but there are only very few literary reports and are not considered while administering the propofol infusion with TCI. Cp50calc of propofol is defined as the calculated plasma concentration of propofol, at which 50% of the patients anesthetized with propofol do not respond to standard surgical stimulus. More studies are required to conclude the influence of nonpharmacokinetic variables such as age, gender, and geographic differences on the plasma concentration of propofol, so that prediction errors will be minimized in the TCI pumps by incorporating these variables in their software. Hence, we designed this study to determine the gender differences in the Cp50calc of propofol required to prevent movement response to surgical stimulus, particularly in the South Indian population.