BACKGROUND: We performed this study to evaluate the appropriate effect-site concentrations of propofol and alfentanil for LMA insertion in ambulatory breast surgery without neuromuscular blockade.

METHODS: Seventy-three ASA physical status 1 patients were enrolled. The administration of propofol and alfentanil was titrated versus bispectral index (BIS < 60), systolic blood pressure (SBP ≥ or = 80 mmHg) and heart rate (HR ≥ or = 50/min), respectively. The condition of LMA insertion was assessed as grade 1 (excellent), 2 (acceptable), and 3 (poor) according to gag, cough, movement, and laryngospasm. We recorded SBP, HR and BIS before and after LMA insertion, the effect-site concentrations of propofol and alfentanil at the time of LMA insertion, and the LMA removal time at recovery.

RESULTS: The condition of LMA insertion at first attempt was grade 1 in 71.6% of patients, grade 2 in 20.3%, and grade 3 in 8.1%. After the first attempt at LMA insertion, movement occurred in 25.7% and the BIS increased above 60 in 31.5%. The range of the effect-site concentrations of propofol and alfentanil at the first attempt were 2.0 6.0 (3.7 ± 0.7)µg/ml and 30.0 150.0 (71.6 ± 24.4) ng/ml, which reflected a large inter-individual variability. The incidences of hypertension, tachycardia, hypotension, and bradycardia were 6.8%, 1.4%, 11.0% and 5.5%, respectively. The mean LMA removal time was 4.7 min.

CONCLUSIONS: LMA was inserted successfully in 91.7% at first attempt and removed promptly at recovery. Movement and increase of BIS above 60 occurred frequently after the first attempt of LMA insertion with the effect-site target-controlled infusion of propofol and alfentanil without neuromuscular blockade.