The total amount of propofol was significantly less in group N+P ( 249.8 121.7 mg ) than in group P ( 310.3 122.4 mg ) ( P = .022 ) , and the mean concentration of propofol was significantly less in group N+P ( 1.81 0.34 g/mL ) than in group P ( 2.05 0.44 g/mL ) ( P = .006 ) .