Effects of different doses of dexmedetomidine in inhibition of cardiovascular response to endotracheal intubation

Objective To compare the effects of different doses of dexmedetomidine in inhibition of cardiovascular response to endotracheal intubation. Methods One hundred and twenty ASA Ⅰ or Ⅱ patients, aged 18-60 yr, weighing 45-80 kg, scheduled for upper abdominal surgery, were randomly assigned to one of 4 groups （n = 30 each）： control group （group C）; low, median and high doses of dexmedetomidine groups （group M1-3） .In group M1-3, 15 min before anesthesia induction, dexmedetomidine 0.25, 0.5 and 1.0 μg/kg were infused over 15 min respectively, while normal saline 15 ml was given instead of dexmedetomidine in group C. After anesthesia induction, tracheal intubation was performed when the BIS value ≤ 60 and it was maintained for 5 s. The patients were mechanically ventilated. BP and HR were recorded before infusion of dexmedetomidine （T0）, before intubation （T1）, immediately after intubation （T2） and at 1, 3, 5 and 10 min after intubation （T3-6）. Venous blood samples were also taken at the same time to measure the plasma concentrations of epinephrine （E） and norepinephrine （NE）. Results Compared with T0, HR was significantly decreased at T1 in group M1-3, BP was significantly increased at T1 in group M3, and the plasma concentrations of E and NE were significantly increased at T4-6 in group C and M1（P 〈0.05）. BP and HR were significantly lower at T2, while higher at T3-5 in group C and M1than at T1 （P 〈 0.05）. BP at T1-6 was significantly higher in group M3 than in group M2 （P 〈 0.05）. Conclusion When the dose of dexmedetomidine reaches 0.5 μg/kg, it may effectively inhibit the stress reaction to noxious stimulation. Key words: Dexmedetomidine; Intubation,intratracheal; Stress