Effects Of Dexmedetomidine Different Infusion Speed On Hemodynamic Responses In Elderly Hypertensive Patients During Anesthesia Induction

Background The key issue of managing the elderly patients with essential hypertension is maintaining stable hemodynamics during anaesthetic induction.The plasma catecholamine level of aged may fluctuate violently at the induction and intratracheal intubation,which can lead to serious complications like myocardial ischemia and hypoxia by disrupting the stability of the hemo-dynamics.Dexmedetomidine is a highly selective 2-adrenergic receptor agonist. Dexmedetomidine offers beneficial pharmacological properties, providing dose-dependent anxiolytic,sedation, anal-gesia,sympatholytic and anesthetic-sparing effects,can helps for a quicker recovery after general anesthesia.Dexmedetomidine also attenuated hemodynamic responses to tracheal intubation. How-ever,intravenous administration of regular loading dose dexmedetomidine in 10 minutes often causes serious hemodynamic effects,including bradycardia, initial hypertension and later hypo-tension. We supposed that the cause of this hemodynamic responses probably was correlated with rapid intravenous transfusions of a higer doses of dexmedetomidine. We tried to prelong infusion time of the loading dose of dexmedetomidine for reducing hemodynamic impact in our study.Objective To investigate the influence of the same doses of dexmedetomidine hydrochloride with different infusion velocity on hemodynamics,plasma norepinephrine and side effect of cardio-vascular in elderly patients with essential hypertension.Methods 49 elderly patients with essential hypertension undergoing endotracheal general anesthesia,aged 65 to 80 years in Zhongda Hospital affiliated to Southeast University were enrolled in the study from October 2014 to March 2015. The protocol was approved by Zhongda Hospital ethics committee.The patients were randomly divided into two groups,the observational group and the control group.American Society of Anesthesiologists(ASA)clinical status of all patients enrolled were Ⅱ～Ⅲ.In observational group,dexmedetomidine was administered intravenously at doses of 0.5μg/kg/30min thirty minutes before anesthesia induction.Normal saline 48ml dissolved dex-medetomidine hydrochloride 200μg and dexmedetomidine hydrochloride was dubbed 4μg/ml. In control group,dexmedetomidine was administered in intravenously at doses of 0.5μg/kg/10min thirty minutes before induction of anesthesia.General anesthesia was induced with sufentanil, propofol,rocuronium.Hemodynamic values included heart rates(HR),systolic blood pressure (SBP),diastolic blood pressure (DBP)and mean arterial pressure(MAP),were recorded baseline (T0),10 minutes(Tl),30minutes(T2) after infusion,after anesthesia induction(T3),before endotracheal intubation(T4),and 1,3,5 minustes after anesthesia indubation(T5,T6,T7).Plasma norepinephrine concentrations were measured at T0,T1,T3,T4,T6.The incidences of adverse cardiovascular responses and the doses of rescue medicine were recorded.Results 49 patients were involved in the experimental statistics.According to the sexuality, age height,body weight,BMI,ASA,clinical classification of hypertension had no significant difference(P>0.05) between the two groups.The HR at T1,T2,T3 were higher in observational group than control group(P<0.05).The SBP was significantly lower in observational group than control group at T1(P<0.05) and significantly higher in observational at T3,T4(P<0.05).The MAP was significantly lower in observational group than control group at Tl(P<0.05) and significantly higher in observational at T2(P<0.05).The levels of NE was significantly higher in observational group than control group at T1,T3,T4(P<0.05).The incidences of bradycardia and hypotension were significantly lower in observational group than control group during the observation period (P<0.05).The consumption of atropine or phenylephrine was significantly less in observational group (P<0.05).Conclusions These results confirm that the slower infusion of the loading doses of dexmedetomidine can reduce the incidences of bradycardia and hypotension.It might be related to keeping plasma norepinephrine levels stable.