Effect Of Dexmedetomidine On Norepinephrine Efficacy During General Anesthesia

ObjectiveTo investigate the effect of dexmedetomidine（Dex）on the hemodynamic response to norepinephrine（NE）during general anesthesia.MethodsAfter obtaining patient consent and signing informed consent,90 patients with general anesthesia were divided into three groups randomly:group A(0.3μg·kg^-1 Dex,n=30),group B(0.5μg·kg^-1 Dex,n=30)and group C（saline,n=30）.Upon arrival in the operating room,standard monitoring equipment was connected to the patient:electrocardiogram（ECG）,pulse oximeter（SpO₂）.By the placement of left radial arterial catheters under local anesthesia,the patient’s arterial blood pressure was monitored.A peripheral intravenous line was inserted in a large left forearm vein to start intravenous fluid therapy immediately.The infusion rate was controlled to be 4 ml·kg^-1·h^-1 for the first 10 kg,2 ml·kg^-1·h^-1 for the second 10 kg,and 1ml·kg^-1·h^-1 for each 10 kg thereafter.No premedication was administered.15 min prior to general anesthesia induction,0.3μg·kg^-1,and 0.5μg·kg^-1 Dex was delivered in group A and group B for 10 min,saline was delivered in the same manner in group C.Before induction of general anesthesia,systolic blood pressure（SBP）,heart rate（HR）and mean arterial pressure（MAP）were recorded every 10 s.The average value was calculated as the baselines after 6 times.The baselines of SBP,HR,and MAP were respectively recorded as SBP1,HR1,and MAP1.Patients in all groups were given propofol(2.5 mg·kg^-1 iv),fentanyl(3μg·kg^-1 iv)and cis-atracurium(0.15 mg·kg^-1 iv)at induction.After muscle-relaxation,the endotracheal intubation used Video Laryngoscope had to be performed within 30 s at one time.Then,propofol was continuously administered at 4mg·kg^-1·h^-1 for anesthesia maintenance.In the course of the study,all operations were conducted by the same anesthesiologist for maximum accuracy.If the systolic blood pressure was less than the 80%baseline after intubation,NE was administered at 0.1μg·kg^-1·min^-1 until the one-minute mean of SBP reaching the baseline.The consumption and the duration of NE were recorded.Results1.There were no significant differences in age,gender,height,weight and BMI between the three groups（P>0.05）.2.Hemodynamic:At baseline,HR in group C was significantly greater than that in group A（P=.018）and group B（P=.019）.There were no significant differences in SBP,HR,and MAP between the three groups during the rest of the time（P>0.05）.3.NE:Compared with group C,the consumption of NE was more than group A（P=.000）and group B（P=.000）.The duration of group A（P=.000）and group B（P=.000）was higher than Group C.There was no difference in duration（P=.974）and consumption（P=.898）of NE between A and B groups.ConclusionDex reduces the hemodynamic response to NE during general anesthesia,manifested as the increasing duration and dose of NE.