In a double-blind study, propofol (P) 2-2.5 mg.kg-1 preceded by saline (Sal) or alfentanil (A) 20-30-mu-g.kg-1 was used for anaesthetic induction in 59 young patients of ASA physical class I or II, premedicated with oxycodone 0.1 mg.kg-1 and atropine 0.01 mg.kg-1 i.m. The patients were randomly allocated to one of the four groups: Group 1 Sal + P2.5, Group 2 A20 + P2.5, Group 3 A30 + P2.5 and Group 4 A30 + P2. Pain on injection of propofol occurred in 67, 36 and 7% of the patients in the Sal + P2.5, A20 + P2.5 and A30 + P2 groups, respectively, but not at all in the A30 + P2.5 group. Intubating conditions were assessed as good, moderate, poor or impossible on the basis of jaw relaxation, ease of insertion of the tube and coughing on intubation, each on a three-point scale. In impossible cases, suxamethonium was used. In the Sal + P2.5 group, the frequencies of good, moderate, poor and impossible intubating conditions were 0, 38, 8 and 54% respectively. The corresponding figures in the A30 + P2.5 group were 43, 46, 7 and 14% (P < 0.05 between the groups). The other groups did not differ significantly from the Sal + P2.5 group. After injection of propofol, both systolic and diastolic arterial pressures decreased significantly in all other groups, with the exception of diastolic pressure in the Sal + P2.5 group, whereas heart rate did not differ from the control level. After intubation, systolic arterial pressure increased statistically significantly in the Sal + P2.5 and A30 + P2 groups and diastolic arterial pressure in all other groups with the exception of the A30 + P2.5 group when compared with the corresponding preceding values. After intubation, heart rate decreased significantly in the A30 + P2.5 and A30 + P2 groups. The mean QTc interval of the ECG was always in the normal range. It is concluded that the best method was the combination of alfentanil 30-mu-g.kg-1 and propofol 2.5 mg.kg-1. It caused no pain on injection of propofol, offered satisfactory (good or moderate) intubating conditions in 79% of the patients and prevented the cardiovascular intubation response.
