Clinical Pharmacodynamic Studies Between Dexmedetomidine And Propofol During General Anesthesia Induction

ObjectiveTo investigate the clinical pharmacodynamic interaction between dexmedetomidine and propofol for loss of eyelash reflex(LOER), loss of consciousness (LOC), and to compare the effects of different load dosages of dexmedetomidine on hemodynamics for endotracheal intubation during general anesthesia induction with propofol, then to research rational load dosage of dexmedetomidine with propofol for clinical anesthesia. To investigate the interaction of sedative and hypnotic between dexmedetomidine and propofol during anesthesia induction.Methods(1) Exploration of proper load dosage of dexmedetomidine with propofol for induction of general anesthesia in patients:60ASAⅠ-Ⅱlevel patients (men and women each30cases) undergoing elective surgery were randomly divided into five groups(n=12):saline control group(C group), dexmedetomidine given0.25μg·kg-1,0.50μg·kg-1,0.75μg·kg-1,1.00μg·kg-14groups (D,-4). The group uses Graseby3500pump dexmedetomidine within10minutes before induction of anesthesia infusion is completed, after all the patients received TCI of propofol, with an initial target concentration of1.0μg·mL-1, then increased0.50μg·mL-1step by step until the patients unconsciousness. In each group, MAP, HR and SpO2were monitored at pre-induction(T0);5min(T1),10min(T2) after the treatment; eyelash reflex disappears (T3); loss of consciousness (T4); before intubation(T5); lmin(T6),3min(T7) after intubation. Record the concentration of propofol effect chamber (PCe) and dose(P) when eyelash reflex disappear(T3), loss of consciousness (T4).(2) Effect of different dosages of dexmedetomidine on anaesthetic depthin patients during induction of general anesthesia with propofol:50ASA I Ⅱ level patients (26males and24females) undergoing elective surgery were randomly divided into five groups(n=10):saline control group(C group), dexmedetomidine given0.25μg·kg-1,0.50μg·kg-1,0.75μg·kg-1,1.00μg·kg-14groups (D1～4). The group uses Graseby3500pump dexmedetomidine within10minutes before induction of anesthesia infusion is completed, every3min after the treatment line alert-Sedation (OAA/S) score and record the BIS value. After all the patients received TCI of propofol,TCI of propofol was started with initial target concentration of1.0μg·mL-1, then increased0.50μg·mL-1according to the OAA/S score and BIS value, step by step until the OAA/S score1. In each group, recorded before induction (To), after giving dexmedetomidine loading dose3min(T1),6min(T2),9min(T3), OAA/S score1point (T4), before intubation(T5), after intubation lmin(T6),3min(T7) BIS, heart rate (HR), mean arterial pressure (MAP) at each time. Results(1) Exploration of proper load dosage of dexmedetomidine with propofol for induction of general anesthesia in patients:Compared with T0, HR and MAP in group D1were decreased significantly at T6to T7(P<0.05); HR and MAP in groups D2and D3at T1～T5were decreased (P<0.05); HR in group D4were decreased at various time points (P<0.05), the MAP at T2to T3was significantly increased(P<0.05). Concentration of propofol effect chamber(PCe) and dosage(P) in groups D2, D3and D4at T3toT4were significantly decreased than in groups C and D1(P<0.05). In group D4, the incidence of respiratory depression and bradycardia was more than the other groups significantly.(2) Effect of different dosages of dexmedetomidine on anaesthetic depthin patients during induction of general anesthesia with propofol:After giving dexmedetomidine loading dose, in groups D2, D3and D4patients BIS gradually decline. Induction began, five patients BIS were significantly decreased. In group C and D1BIS changes after intubation compared with before intubation(T5) was significantly higher (P<0.05). Compared with T0, HR and MAP in group C and D1at T6～T7increased significantly(P<0.05);HR and MAP in groups D2at T2～T5were decreased (P<0.05); HR in group D3and D4were decreased at T1～T5(P<0.05), the MAP at T2～T4was significantly increased(P<0.05). Conclusion(1) The dosage of dexmedetomidine ranging from0.50to0.75μg·kg-1for induction of anesthesia with propofol can effectively stablize the hemodynamics. Dexmedetomidine can significantly reduce the effects of propofol concentration and dosage, and present the linear correlation between each other in the loading dose0to1.00μg·kg-1range, When the dose>0.75μg·kg-1with ceiling effect.(2) Dexmedetomidine can certainly reduce the BIS and enhance the effect of propofol sedation. As the dose increased in the loading dose0to1.00μg·kg-1range, the stronger its sedative effect, but increasing the dose of dexmedetomidine had no significant effect on propofol sedation.