Abstract: AIM: To evaluate the effects of two single preanesthetic doses of dexmedetomidine (0.5 μg/kg and 1.0 μg/kg) on bispectral index (BIS) and hemodynamic changes undergoing endotracheal intubation under induction anesthetic with sevoflurane inhalation.METHODS: In a double-blind and random study, 45 patients scheduled for gynaecologic laparoscopy operation were divided into 3 groups (n=15 for each). Patients in Group A were anesthetized with inhalation of sevoflurance; Patients in Group B and Group C were anesthetized with 0.5 μg/kg and 1.0 μg/kg dexmedetomidine infusion before anesthetic induction with sevoflurane in oxygen by face mask.The changes in hemodynamics and BIS were observed at time points before induction (T₀ ), after induction (T₁ ), and 5 min (T₂ ) after intubation. Time going into sleep, time for the BIS to 60, time carrying intubation, anesthesia and operation, times carrying vital capacity breath ,and the adverse effect were also observed.RESULTS: Compared with the values at T₀, the BIS, the heart rate and blood pressure were decreased remarkably at T₁ (P<0.05). At T₂ , the blood pressure was significantly higher than those at T₀ and T₁ in Group A (P<0.05). Compared with Group A, the BIS, heart rate and blood pressure were lower in Groups B and C(P<0.05)at T₁,T₂. The time going into sleep, time for the BIS to 60 and time carrying intubation were shorter in Group B and C (P<0.05), especially in group C.CONCLUSION: Both dexmedetomidine 0.5 μg/kg and 1.0 μg/kg caused sedation and significantly decreased hemodynamics and stress reaction to endotracheal intubation during sevoflurane anesthesia induction.Dexmedetomidine 1.0 μg/kg was better than dexmedetomidine 0.5 μg/kg.Severe bradycardia and hypotension during anesthesia should be noticed.

Key words: Dexmedetomidine, Sevoflurance, Hemodynamics, Bispectral index