ABSTRACT
To evaluate whether midazolam has analgesic properties in humans after intravenous injection we studied the influence of a subhypnotic dose of midazolam (50 micrograms/kg) on the cumulative alfentanil consumption in 53 patients during extracorporeal shock wave lithotripsy (ESWL) using a patient-controlled analgesia system (PCAS). In a randomised double blind fashion all patients received either midazolam or an equal volume of saline (placebo) prior to ESWL. Heart rate and arterial blood pressure were measured before and during ESWL. Alfentanil consumption was assessed 20 minutes after injection of midazolam or placebo, respectively. All patients received oxygen via face mask. In patients older than 60 years (median: 70 years, range: 61-88 years) pretreatment with midazolam resulted in a significantly lower cumulative alfentanil consumption (0.41 vs 0.97 mg; p = 0.027) compared with patients younger than 60 years after midazolam pretreatment (0.84 vs 0.71 mg; p = 0.27). Mean arterial pressure also was significantly lower in the former compared with the latter group, while heart rate remained unchanged. In contrast, in patients younger than 60 years (median: 47 years, range: 24-56 years) no significant differences were observed between the midazolam and the placebo group. Thus, low dose intravenous midazolam pretreatment led to a significant decrease of alfentanil consumption in patients beyond 60 years of age. We conclude that subhypnotic doses of midazolam are capable of reducing alfentanil demand in elderly but not in younger patients during ESWL.
