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 pretreatment with midazolam at two different doses (0.025 and 0.05 mg x kg(-1)), with placebo, on the induction dose requirements of propofol in two different age groups. We enrolled 120 patients: 60 younger patients (aged 18-35 years) and 60 older patients (aged over 60 years). All patients received 0.75 microg x 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 propofol. Propofol dose requirement was recorded, as were cardiovascular parameters and the occurrence of significant apnoea (> 60 s). Midazolam pretreatment was associated with a significant reduction in propofol dose requirement in both younger and older patients. The reduction in older patients was significantly greater than the equivalent response in younger groups. There was no demonstrable benefit in terms of improved cardiovascular stability 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.