Clinical study on best dosage of continuous intravenous remifentanil combined with propofol for anesthetic induction and tracheal intubation

Objective:To investigate the best dosage of continuous intravenous remifentanil combined with propofol for anesthetic induction and tracheal intubation.Methods:Eighty ASA Ⅰ ~ Ⅱ patients were randomly allocated to one of four groups of 20 each:group A,B,C and D.Anaesthesia was induced with remifentanil 0.4,0.5,0.6 or 0.7μg.kg-1.min-1 for group A,B,C and D,respectively.Each patient was administered 1.5 mg.kg-1 propofol 2 min after the start of remifentanil infusion,and 0.6 mg.kg-1 rocuronium 1.5 min after propofol injection.Tracheal intubation was performed 1.5 min after rocuronium injection,and each patient was administered 0.1μg.kg-1.min-1 remifentanil and 4 mg.kg-1.h-1 propofol at this time point.Noninvasive blood pressure and heart rate were recorded before anesthetic induction(T1),immediately before intubation(T2),immediately after intubation(T3),1 min after intubation(T4),2 min after intubation(T5),3 min after intubation(T6),4 min after intubation(T7),and 5 min after intubation(T8).The adverse effects like cough and muscle rigidity and use of vasoactive agents were also recorded.Results:MAP and HR decreased in all groups at T2(P0.05),and HR was lower in group D than in group A at this time point(P0.05).After intubation,MAP and HR increased immediately and were higher compared with the baseline value till T5 in group A(P0.05).There was no difference in MAP and HR compared with the baseline value after intubation in group B and C(P0.05).MAP remained below the baseline value after intubation till T8 in group D(P0.05).There were more patients needing vasoactive agents in group A and D than in group B and C(P0.05).No patient among the four groups presented with cough and muscle rigidity.Conclusion:Continuous intravenous remifentanil for 5 min produced a dose-related attenuation of the haemodynamic response to tracheal intubation without adverse effects like cough and muscle rigidity,and remifentanil 0.5-0.6μg.kg-1.min-1 combined with 1.5 mg.kg-1 propofol maintained more stable hemodynamics.