Effects of dexmedetomidine pretreatment on haemodynamics and bispectral index during anesthetic induction in patients undergoing cardiac valve replacement surgery with cardiopulmonary bypass

Abstract

Objective To evaluate the influence of dexmedetomidine(Dex)(highly selective α2-adrenergic receptor agonist) on haemodynamics and bispectral index (BIS) during anesthetic induction in patients undergoing valve replacement surgery.Methods Thirty NYHA class Ⅱ or Ⅲ patients,aged between 30 y and 70 y,undergoing cardiac value replacement with cardiopulmonary bypass,were randomly divided into two groups (n=15):Dex group(group D) and control group(group C).In group Dex,pump diluted with saline to 50 ml of Dex (4 mg/L)0.5 μg/kg was administered iv 10 min before the induction of anesthesia,while in group C,same volume of 0.9％ normal saline was given.The patients were premedicated with intramuscular morphine and scopolamine.Anesthesia was induced with 0.06 mg/kg,fentanyl 6 μg/kg,etomidate 0.3 mg/kg and pipecuronium 0.10 mg/kg.Anesthesia was maintained with midazolam,fentanyl,intermittently.In two group,heart rate(HR),arterial blood pressure(ABP)[systolic blood pressure(SBP),diastolic blood pressure(DBP),mean arterial pressure(MAP)] and bispectral index(BIS) were recorded at the time before Dex infusion(T1),5 min after loading dose(T2),10 min after loading dose(T3),1,3 min after anesthesia induction(T4,T5),just before endotracheal intubation(T6),endotracheal intubation(T7) and 1,3,5 min after endotracheal intubation(T8-10).Results BIS of T2,T3 in group D was decreased significantly [from(92.6±2.5) to (73.2±1.9) and (70.1±2.3)](P＜0.05 or P＜0.01) compared with T1.During anesthesia induction compared with T3,BIS in both groups were decreased significantly.During endotracheal intubation compared with T6,BIS of T7 (34.8±2.2) was increased significantly in group C(P＜0.05 or P＜0.01),while BIS in group C were similar to the initial values.Compared with group C,BIS decreased significantly at time T2～5、T7 in group D (P＜0.05 or P＜0.01).Before anesthesia induction compared with T1,ABP of T2、T3 in group D was increased slightly,HR of T2、T3 was decreased significantly (P＜0.05 or P＜0.01); During anesthesia induction compared with T3,ABP and HR in both groups were decreased significantly.Compared with T6,DBP,MAP and HR of T7,T8 were increased slightly,that of T9,T10 were similar to the values in group D.During endotracheal intubation,while ABP and HR of T7-T1o was increased significantly in group C (P＜0.05 or P＜0.01).Compared with group C,SBP,MAP of T4-T10 and DBP of T3-T10 were increased significantly in group D.HR of T2-T10 were decreased significantly in group D (P＜0.05 or P＜0.01).Conclusions Dex pretreatment might decrease BIS and alleviate haemodynamics reaction during anesthetic induction in patients undergoing valve replacement surgery with cardiopulmonary bypass. Key words: Dexmedetomidine; Valve replacement; Bispectral index; Stress reaction; Hemodynamics