Effects of different dose of dexmedetomidine on minimum alveolar concentration of sevoflurane in patients undergoing upper abdominal surgery

AIM To observe the effects of different dose of dexmedetomidine on minimum alveolar concentration(MAC) of sevoflurane in patients undergoing upper abdominal surgery.METHODS Adult patients (aged from 40 to 60 years) undergoing elective upper abdominal surgery with ASAⅠorⅡwere randomly divided into group D_0,D_1 and D_2.Fifteen minutes before anesthesia induction,patients in the group D_1 and D_2 were intravenously administered with dexmedetomidine 0.4 and 0.8μg·kg~(-1) respectively,while patients in the group D_0 were intravenously administered with same amount of sodium chloride injection.Inhalation of sevoflurane was started after induction of anesthesia with propofol,fentanyl and suxamethonium.The end-tidal concentration of sevoflurane during maintenance of anesthesia was determined according to up-down method.After at least 15 minutes of equilibration and full recovery from suxamethonium-induced muscle relaxation was ensured,skin incision was performed.The patient' s somatic responses was evaluated when skin incision.MAC of sevoflurane was the mean of end-tidal concentration of sevoflurane of each crossover pair.The changes of blood pressure, heart rate and bispectral index were also observed.RESULTS The MAC of sevoflurane in the group D_0,D_1 and D_2 was(1.42±0.25)%,95%CI 1.24%- 1.60%;(1.06±0.25)%,95%CI 0.88%- 1.24%;and(0.82±0.19)%,95%CI 0.70%- 0.93%,respectively.The levels of MAC in the group D_2 and D_0 were significant lower than that in the group D_0(P0.05).Blood pressure and heart rate in the D_1 group and D_2 decreased gradually,but some patients need atropine to keep heart rate.Bispectral index in the group D_1 and D_2 decreased to 84+3 and 75±4 after dexmedetomidine was used,and the difference was significant(P0.01). CONCLUSION Intravenous administration of dexmedetomidine 0.4 and 0.8μg ? kg~(-1) before anesthesia induction could decrease the MAC of sevoflurane by 25.4%and 42.3%respectively,therefore reduce the need of sevoflurane in patients undergoing upper abdominal surgery.