Thiopentone requirements in adults after varying pre-induction doses of fentanyl

The thiopentone dose needed for satisfactory induction of anaesthesia was determined in 60 adult patients using a double-blinded study design. No premedication was given. The effect of pretreatment with four different doses of fentanyl on ED50 for thiopentone was determined and compared with a control group not receiving fentanyl. The cardiovascular effects of the combinations were also studied. ED50 for thiopentone was reduced from 4.0 mg.kg-1 in the control group to 2.2 mg.kg-1 in patients receiving fentanyl 5.0 micrograms.kg-1. Only in the group of patients receiving fentanyl 5.0 micrograms.kg-1 was there no significant change in systolic arterial blood pressure. An increased heart rate was noted in patients induced with thiopentone in combination with fentanyl 0.625 micrograms.kg-1. No adverse effects of thiopentone, fentanyl or the combinations were noted.