A comparison between midazolam co-induction and propofol predosing for the induction of anaesthesia in the elderly

In a prospective, double-blind, randomised, placebo-controlled trial, we have compared the effects of midazolam co-induction with propofol predosing on the induction dose requirements of propofol in elderly patients. We enrolled 60 patients aged > 70 years, attending for urological surgery. The patients were allocated randomly to one of three groups, to receive either midazolam 0.02 mg.kg(-1), propofol 0.25 mg.kg(-1), or normal saline 2 ml (placebo) 2 min prior to induction of anaesthesia using propofol 1% infusion at 300 ml.h(-1). The propofol dose requirements for induction were recorded for two end-points (loss of verbal contact and insertion of an oropharyngeal airway). Cardiovascular parameters were recorded at 1-min intervals for each patient until induction was complete. The midazolam group showed a significant reduction in propofol dose requirements for induction (p = 0.05) compared to the placebo group. The propofol group did not show a significant dose reduction compared to placebo. There were no demonstrable differences in terms of improved cardiovascular stability between groups. We conclude that propofol predosing does not significantly reduce the induction dose of propofol required in the elderly, and there were no cardiovascular benefits to either midazolam co-induction or propofol predosing in the elderly.