The target plasma concentration of propofol required to place laryngeal mask versus cuffed oropharyngeal airway

To determine the target plasma concentration of propofol required to place either a laryngeal mask airway (LMA) or a cuffed oropharyngeal airway (COPA), we started a continuous target-controlled infusion of propofol in 60 ASA physical status I or II unpremedicated patients scheduled for minor orthopedic surgery with peripheral nerve block. The target plasma concentration of propofol was initially set at 2 μg/mL. When the effect- site calculated concentration of propofol was equal to the plasma concentration according to the computer simulation, the target plasma concentration was increased by 0.5-μg/mL steps until successful placement of either the LMA (n = 30) or the COPA (n = 30). The mean target plasma concentration of propofol required to place a LMA was 4.3 ± 0.8 μg/mL compared with 3.2 ± 0.6 μg/mL to place a COPA (P <0.001). To successfully place the airways in 95% of patients, the target plasma concentration of propofol had to be increased up to 4 μg/mL for the COPA and 6 μg/mL for the LMA. We conclude that placing a LMA in healthy, unpremedicated patients requires target plasma concentrations of propofol higher than those required for placing a COPA. Implications: We evaluated the use of target-controlled infusion of propofol to place extratracheal airways in this prospective, randomized study and demonstrated that the target plasma concentration of propofol required to successfully place a laryngeal mask in >95% of healthy, unpremedicated patients is 6 μg/mL, compared with 4 μg/mL to place a cuffed oropharyngeal airway.