Effect of midazolam pretreatment on induction dose requirements of propofol in combination with fentanyl in younger and older adults

In a double-blind, randomised trial, we compared the effects of pretreatmen t with midazolam at two different doses (0.025 and 0.05 mg.kg(-1)), with pl acebo, on the induction dose requirements of propofol in two different age groups. We enrolled 120 patients: 60 younger patients (aged 18-35 years) an d 60 older patients (aged over 60 years). All patients received 0.75 mug.kg (-1) of fentanyl, plus a blinded pretreatment with either saline or one of two doses of midazolam. Induction continued with a fixed rate infusion of p ropofol. Propofol dose requirement was recorded, as were cardiovascular par ameters and the occurrence of significant apnoea (> 60 s). Midazolam pretre atment was associated with a significant reduction in propofol dose require ment in both younger and older patients. The reduction in older patients wa s significantly greater than the equivalent response in younger groups. The re was no demonstrable benefit in terms of improved cardiovascular stabilit y or reduction in the incidence of apnoea. Caution is advised in the use of midazolam as an agent for co-induction with propofol in the elderly.