Ventilatory CO2-response after alfentanil and sedative premedication (etomidate, diazepam and droperidol). A comparative study with human volunteers.

The ventilatory response to CO2 after intravenous bolus injection of alfentanil 15 micrograms/kg was studied in a group of 10 healthy volunteers of both sexes, aged 19 to 30 years. Following randomized intravenous premedication with either placebo, diazepam 5 mg, droperidol 5 mg or etomidate 10 mg, a total of four test-series were performed with each individual in two-weekly intervals, in order to assess the additive effect of central depressants on opiate-induced respiratory depression. CO2-response curves were obtained during six-minute rebreathing periods up to 60 minutes after alfentanil. Slope as well as position of the curves were compared with pre-drug control values. In contrast to previous work with fentanyl 4 micrograms/kg, CO2-response curves after alfentanil 15 micrograms/kg were usually displaced to the right without concomitant decreases in slope. Ventilation almost completely returned to control levels after one hour. Due to strong inter- and intraindividual variations, no clearly significant differences could be observed between the premedication groups. Alfentanil plasma concentrations, determined by radioimmunoassay at 1, 3, 6, 10, 20, 30, 45, 60, 75 and 120 minutes after injection, showed only a poor correlation to the changes of the CO2-response curves.