Preinjection Dexmedetomidine On The Half Effective Plasma Concentration Of Etomidate Inhibiting Tracheal Intubation Response In Elderly Patients

1.Background and objectiveEndotracheal intubation stress can lead to severe hemodynamic response.Due to decreased ability of sustaining steady in elderly patients,adverse effects including arrhythmia,myocardial ischemia,and even heart failure,etc.can be easily occurred.Literature reports 66%of elderly perioperative deaths are due to cardiovascular events.Etomidate is often used for anesthesia induction for elderly patients due to small inhibition on respiratory cycle.But some literature questions whether etomidate can effectively inhibit endotracheal intubation and the dose.There is a close relationship between the pharmacodynamics and concentration.Administration with intravenous injection leads to attenuation,and target controlled infusion can maintain stable blood drug concentration and avoid the disadvantage of manual dosing.Blood drug concentration of anesthetic drug should fit different stimulus intensity.And target controlled infusion of etomidate assisting sufficient opioids carn effectively suppress intubation response.Understanding the median effective dose of plasma target concentration(CP50)facilitates to set the reference initial concentration according to the target close to the efficacy.Dexmedetomidine has sedation,analgesia,and anti-sympathetic effects,which can assist anesthesia induction in the elderly patients.This study aims to observe the influences of pre-injection of dexmedetomidine on the role of etomidate in inhibiting tracheal intubation response CP50 of the elderly patients by target controlled technology,evaluate its safety and provide reference for clinical rational drug use.2.MethodsThe elderly patients undergoing selective operation with general anesthesia were randomly divided into two groups.Patients in experimental group(Group D)were adminstated dexmedetomidine 0.5ug/kg 10 min before induction.Meanwhile,patients in control group(group C)were administrated the same volume of saline.The modified Dixon's up-and-down sequential method was used to determine the target plasma target-controlled infusion concentration of etomidate.The first concentration of etomidate was 0.30 ug/ml in Group D and 0.40 ug/ml in Group C according to the pre-test.The adjacent concentrations of each group increased or decreased by 0.1ug/ml,when the sixth turning point appeared,the trial was ended.The SBP,DBP,MAP,HR,Sp02,OAA/S and BIS values were measured and recorded immediately at the baseline(TO),5 min(T1)and 10min(T2)after pre-injection,disappear of consciousness(T3),balance of plasma and effective targeted concentration of etomidate(T4),immediate before intubation(T5),lmin(T6),3min(T7)and 5min(T8)after tracheal intubation.3ml of arterial blood was sampled at TO and T8 to examine the plasma concentration of catecholamine.The adverse reactions were recorded.SPSS13.0(SPSS Inc,Chicago,IL)was used for statistical analysis.The measurement data was presented as mean±standard deviation(x±s)or the median(quartile).Enumeration data was represented by frequency,Fisher exact test was used for comparison between groups.P<0.05(double side)was considered as statistically significant differences.Probit analysis was used to calculate the CP50 and 95%CI of etomidate in inhibiting the endotracheal intubation responses.Figures were made using Microsoft Excel 2003.3.Results21 patients in group D and 18 patients in group C were enrolled in the study.CP50 of etomidate in inhibiting endotracheal intubation response was 0.62ug/ml(95%CI 0.49-0.76ug/ml)in group D while 0.91ug/ml(95%CI 0.79-1.07ug/ml)in group C.Comparison within the group,SBP and MAP were decreased significantly at T3-T8 of group D and at T4,T5,T8 of group C compared with that at TO(P<0.05);SBP and MAP at T6-T8 of group D were increased significantly compared with that at T5(P<0.05).DEP at T3-T8 of group D and at T4 and T5 of group C were decreased significantly compared with that at TO(P<0.05);DBP at T6-T7 of group D and at T6,T7 and T8 of group C were increased significantly compared with that at T5(P<0.05).HR at T2-T5 and T8 of group D and at T6 of group C were decreased significantly compared with that of TO(P<0.05);HR at T6-T7 of two groups were increased significantly compared with that of T5(P<0.05).Comparison between the two groups,SBP and MAP at T3-T8 of group D were lower than those of group C,and DBP at T4-T8 of group D was lower than that of group C,with statistically significant differences(P<0.05).Comparison within the group,BIS at T1 and T2 of group D were lower than those of group C,and BIS at T4 and T5 of group D were higher than that of group C(P<0.05).Comparison between the two groups,BIS was decreased at T2-T8 of group D and at T3-T8 of group C compared with TO(P<0.05).Different doses of etomidate can make the BIS drop to below 50,which is returned during intubation.Increased dosage of etomidate may lead to deepen anesthesia.During adverse reaction,the incidence of bradycardia were 5.6%and 33.3%in group C and group D,respectively(P<0.05),and the incidence of hypertension were 38.9%and 4.8%in group C and group D,respectively(P<0.05).4.ConclusionsDexmedetomidine can reduce the CP50 of target-controlled infusing etomidate significantly during induction in elderly patients.Dexmedetomidine combined with etomidate can reduce the side effects of the latter,but may interfere with the stability of hemodynamics.