Predicted Effect-site Concentration of Remifentanil for Facilitating Laryngeal Mask Airway Insertion with Propofol Target-Controlled Infusion

Kim, Jong Yeop; Park, Sung Yong; Moon, Bong Ki; Kim, Do Wan; Kim, Jin Soo

Abstract

BACKGROUND
The addition of remifentanil during the propofol induced anesthesia facilitates the insertion of laryngeal mask airway (LMA) with minimal adverse hemodynamic disturbances. This study predicted the optimal effect-site concentration of remifentanil for LMA insertion with propofol target-controlled infusion (TCI).
METHODS
In 25 adults patients, aged 18-60 years, anesthesia was induced with propofol TCI at the effect-site concentration of 4microgram/ml. Two minutes later, the predetermined effect-site concentration of remifentanil was started. The remifentanil concentration was determined using modified Dixon's up-and-down method (0.5 ng/ml as a step size). The first patient was tested at 2.0 ng/ml remifentanil. The insertion of LMA was attempted 3 min after remifentanil TCI began. The response of the patients to the insertion of LMA was classified as either 'movement' or 'no movement'.
RESULTS
The remifentanil concentration at which there was a 50% probability of successful LMA insertion (EC50) was 3.18 +/- 0.53 ng/ml. From probit analysis, the EC50 of remifentanil was 3.10 ng/ml (95% confidence limits, 2.55-4.11 ng/ml), and the EC95 was 4.31 ng/ml (95% confidence limits, 3.64-11.11 ng/ml).
CONCLUSIONS
The predicted effect-site concentration of remifentanil for facilitating LMA insertion was 3.18 ng/ml in 50% of adults during propofol TCI at an effect-site concentration of 4microgram/ml without premedication.