Total consumption of PCS propofol and alfentanil was significantly less in the dexmedetomidine than placebo group with a mean difference of -13.8 mg propofol ( 95 % confidence interval -27.3 to -0.3 ) and -34.5 g alfentanil ( 95 % confidence interval -68.2 to -0.7 ) at the completion of the procedure ( P = 0.044 ) .