Effect of dexmedetomidineon minimum alveolar concentration of isoflurane required to inhibit the body movementduring skin incision

Abstract

：Objective To investigatethe effect of dexmedetomidine on minimum alveolar concentration (MAC) of isofluranerequired to inhibit the body movement during skin incision. Methods Forty-eight ASA Ⅰ or Ⅱ patients aged 40-60 yr withbody mass index of 22-27 kg/m2 undergoing elective upper abdominal surgery under generalanesthesia were randomly divided into 3 groups: control group (group C, n = 15);low dosedexmedetomidine group (group D1, n = 17) and high dose dexmedetomidine group (group D2, n= 16). The patients were unpremedicated. Dexmedetomidine 0.4 and 0.8 μg/kgin normal saline (NS) 15 ml was infused over 15 min before induction of anesthesia in D1and D2 groups respectively. Anesthesia was induced with fentanyl-propofol-succinylcholine.The patients were mechanically ventilated after tracheal intubation. Anesthesia wasmaintained with isoflurane. MAC of isoflurane was determined by up-and-down technique. Theinitial end-tidal isofiurane concentration was set at 1.0%, 0.8% and 0.6% in C, D1 and D2groups respectively. Each time the end-tidal isoflurane concentration wasincreased/decreased by 0.2%. Skin incision was made after 15 min of equilibration, whenthe twitch height returned to more than 90% of its control value. Movement of body andlimbs including swallowing and coughing were carefully looked for when skin incision wasmade. MAC of isoflurane was the mean of end-tidal concentration of isoflurane of eachcrossover pair, and 95 % CI was calculated. Results MAC of isoflurane was significantlydecreased in D1 and D2 groups as compared with group C and in group D2 as compared withgroup D1( P ＜ 0.05or 0.01 ). Conclusion Dexmedetomidine can significantly decrease MAC of isofluranerequired to inhibit the body movement during skin incision in a dose-dependent manner. Key words: Dexmedetomidine; Dose-response relationship, drug; Isoflurane