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 orthop edic surgery with peripheral nerve block. The target plasma concentration o f propofol was initially set at 2 mu g/mL. When the effect-site calculated concentration of propofol was equal to the plasma concentration according t o the computer simulation, the target plasma concentration was increased by 0.5-mu g/mL steps until successful placement of either the LMA (n = 30) or the COPA (n = 30). The mean target plasma concentration of propofol requir ed to place a LMA was 4.3 +/- 0.8 mu g/mL compared with 3.2 +/- 0.6 mu g/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 u p to 4 mu g/mL for the COPA and 6 mu g/mL for the LMA. We conclude that pla cing a LMA in healthy, unpremedicated patients requires target plasma conce ntrations of propofol higher than those required for placing a COPA. Implic ations: We evaluated the use of target-controlled infusion of propofol to p lace extratracheal airways in this prospective, randomized study and demons trated that the target plasma concentration of propofol required to success fully place a laryngeal mask in >95% of healthy, unpremedicated patients is 6 mu g/mL, compared with 4 mu g/mL to place a cuffed oropharyngeal airway.