| ObjectiveDexmedetomidine is a highly selective a2-adrenergic receptor agonist and used widely in perioperative periods,which can inhibit the activity of sympathetic nervous system and exert sedative and analgesic effects without obvious respiratory depression.Dexmedetomidine could affect cardiac electrophysiology balance and cardiac function by changing the permeability of ion channels.Dexmedetomidine could intensify the efferent impulse of vagus nerve,prolong the effective refractory period of myocardial cells,decrease myocardial autonomy,and shorten the abnormally prolonged corrected QT interval（QTc）in patients under general anesthesia.While controversial influence of dexmedetomidine during the perioperative periods on cardiac electrophysiology and function still exists.In the current study,dexmedetomidine was applied to patients undergoing elective surgeries under general anesthesia.The first aim was to observe its influences on cardiac electrophysiology and function perioperatively,and the secondary aim was to explore the optimum dosage of dexmedetomidine whose had minimum negative effects on electrocardiac action and cardiac function during perioperative period to provide some references for rational use in clinical practice.MethodsA total of 81 patients undergoing elective surgeries under general anesthesia,aged 18-65 years,BMI 18.5～30.0 kg/m2,ASA Ⅰ or Ⅱ grade,were randomly divided into 4 groups according to different dexmedetomidine regimens.Groups D1,D2 and D3 received dexmedetomidine loading dose 1,1 and 0.5 μg/kg（infused for 10 min）and maintenance dose 1,0.5 and 0.5 μg·kg-1·h-1,respectively,and control group（group C）was infused with normal saline 50 ml/h for 10 min and maintenance dose 10 ml/h.Electrolyte concentrations of K+,ionized calcium（iCa2+）,Na+ and lactic acid（Lac）were recorded at the time just before dexmedetomidine infusion（T1）,dexmedetomidine loading dose finish（T2）,1 h（T5）after the surgery beginning,surgery ending（T6）,and 1 hour after entering PACU（T7）.Cardiac function parameters including cardiac circulation efficiency（CCE）,cardiac index（CI）,maximum pressure gradient（dp/dt）and stroke volume（SV）were recorded at T1,T2,surgery beginning（T3）,30 min after surgery beginning（T4）,T5,T6 and T7.Hemodynamic indicators including HR,MAP and systemic vascular resistance（SVR）were also recorded at the above time points.Twelve-lead electrocardiograms including PR,QRS,QTc,Tp-e intervals and index of cardiac electrophysiological balance（iCEB）were recorded at T1,T2,T6,T7,24 h（T8）,48 h（T9）,72 h（T10）and 1 month（T11）postoperatively.The surgery types and time,duration of anesthesia（the time from dexmedetomidine or normal saline loading dose infusion beginning to tracheal tube removal）,emergence time from surgery,duration of extubation,dosages of propofol and remifentanil,total fluid intake from entering the operating theater to PACU exiting,and VAS and Ramasy scores in PACU were recorded,respectively.Use of vasoactive drugs and the occurrence of arrhythmia during perioperative period was also recorded.Results（1）Patients’ demographic data and perioperative indicatorsThere were no significant differences among the four groups in the demographic characteristics（gender,Age,Weight,Height,Body mass index,ASA status）（P>0.05）.There were no significant differences in surgery types or time,duration of anesthesia,emergence time from surgery,duration of extubation,total fluid intake from entering the operating theater to PACU exiting,VAS and Ramasy scores in PACU among all groups（P>0.05）.Compared with group C,dosages of propofol in groups D1 and D2 were decreased significantly（P<0、05）.Dosages of remifentanil were decreased significantly in groups D1,D2 and D3（P<0.05）.（2）Changes of electrolyte concentrations and arterial blood gas analysis parameters in the four groupsNo significant differences in changes of K+,iCa2+ and Lac conceutrations existed in any group（P>0.05）.Compared with group C,the concentration of Na+ was increased significantly at T5-T7 in group D1（P<0.05）.Compared with group D1,the Na+ concentration was decreased significantly at T6-T7 in groups D2 and D3（P<0.05）.（3）Changes of cardiac function and hemodynamic parameters in the four groupsCompared with CCE at T1,CCE were decreased significantly in groups D1 and D2 at T3（P<0.05）.Compared with group C,CCE were decreased significantly at T2 and T3 in group D1（P<0.05）and at T2 in group D2（P<0.01）.Compared with group D1,CCE were increased significantly in group D3 at T2-T4（P<0.05）.Compared with group D2,CCE were increased significantly in group D3 at T2 and T3（P<0.05）.Compared with CI at T1,CI were decreased significantly in groups D1 and D2 at T2（P<0.05）.Compared with dp/dt at T1,dp/dt were decreased significantly at T2-T7 in groups D1,D2 and D3（P<0.05）,and at T3-T6 in group C（P<0.05）.Compared with T2,dp/dt decreased significantly at T4-T7 in group D1（P<0.01）and at T4-T6 in groups D2,D3 and C（P<0.05）.Compared with group C,dp/dt decreased significantly at T7 in group D1 and at T4 and T7 in group D2（P<0.05）.Compared with group D3,dp/dt decreased significantly at T7 in groups D1 and D2（P<0.05）.Compared with HR at T1,HR were decreased significantly at T2-T7 in groups D1,D2 and D3（P<0.01）and at T3-T7 in group C（P<0.05）.Compared with T2,HR were decreased significantly at T4 in group D1（P<0.05）and at T3-T6 in group C（P<0.01）.Compared with group C,HR were decreased significantly at T2 in groups D1,D2 and D3（P<0.01）and at T4 in group D1（P<0.05）.Compared with MAP at T1,MAP were increased at T2 and decreased significantly at T6 in group D1（P<0.05）,increased at T2 and decreased at T5 and T6 significantly in group D2（P<0.05）,decreased significantly at T2,T5 and T6 in group D3（P<0.01）,and decreased significantly at T5 in group C（P<0.01）.Compared with MAP at T2,MAP at T5-T7 in group D1,at T4-T7 in group D2,at T6 in group D3,and at T5 in C were decreased significantly（P<0.01）.Compared with group C,MAP were increased at T2-T5 in group D1（P<0.05）and at T2 in group D2 significantly（P<0.05）.Compared with group D1,MAP were decreased significantly at T2 and T3 in group D3（P<0.05）.Compared with group D2,MAP were decreased significantly at T2 in group D3（P<0.05）.Compared with SV at T1,SV were increased significantly at T4 and T5 in group D3（P<0.01）.Compared with group C,SV were increased at T4 in groups D2（P<0.05）and D3 and at T5 significantly in group D3（P<0.01）.Compared with group D3,SV were decreased significantly at T4 and T5 in groups D1 and D2（P<0.05）.Compared with SVR at T1,SVR were increased significantly at T2 in groups D1 and D2（P<0.01）.Compared with SVR at T2,SVR were decreased significantly at T6 and T7 in groups D1 and D2（P<0.01）.Compared with group C,SVR were increased significantly at T2,T4 and T5 in group D1 and at T2 in group D2（P<0.05）.Compared with group D1,SVR was significantly lower at T2-T5 in group D3（P<0.05）.Compared with group D2,SVR at T2 and T3 were significantly lower in group D3（P<0.05）.（4）Changes of ECG indicators in the four groupsCompared with PR intervals at T1,the PR intervals were prolonged significantly at T2,T6 and T7 in groups D1 and D3,at T2 in group D2（P<0.05）,and shortened significantly at T10 in group D3（P<0.01）.Compared with T2,the PR intervals were significantly shortened at T8-T11 in groups D1 and D2（P<0.01）and at T9-T11 in group D3（P<0.01）.Compared with group C,the PR intervals were prolonged significantly at T2 in groups D1 and D2（P<0.01）.Compared with group D3,the PR intervals were prolonged significantly at T2 in groups D1 and D2（P<0.05）.There were no significant differences in QRS intervals within and among the four groups（P>0.05）.Compared with QTc intervals at T1,QTc was prolonged significantly at T2,T6 and T7 in group D1（P<0.01）,at T2 and T6 in group D2（P<0.05）,and at T6-T8 in group C（P<0.01）,while shortened significantly at T2 and T10 in group D3（P<0.05）.Compared with QTc intervals at T2,QTc were decreased significantly at T10 and T11 in group D1 and at T9-T11 in group D2（P<0.05）,while increased significantly at T6 in group D3（P<0.01）and at T6-T8 in group C（P<0.05）.Compared with group C,QTc were significantly prolonged at T2 in groups D1 and D2（P<0.01）,while shortened significantly at T7 and T8 in group D3（P<0.05）.QTc in group D3 was significantly shortened at T2,T6,T7,T9 and T10 compared with group D1（P<0.05）,and shortened significantly at T2 compared with group D2（P<0.01）.There were no statistical differences in Tp-e intervals among the four groups both at T1 and T2（P>0.05）.Compared with group C,Tp-e at T8 in group D1 was prolonged significantly（P<0.01）while shortened significantly in group D3（P<0.05）.Tp-e in group D3 were shortened significantly at T7-T9 compared with group D1（P<0.05）and at T8 and T9 compared with group D2（P<0.05）.Compared with iCEB at T1,iCEB at T2,T6-T8 in groups D1 and D2（P<0.01）,at T6 in group D3（P<0.01）,and at T6 and T7 in group C were significantly prolonged（P<0.01）.Compared with iCEB at T2,iCEB at T10 were shortened significantly in groups D1 and D2（P<0.01）,at T6 was prolonged and at T8 was shortened significantly in group D3（P<0.05）,and at T6 and T7 was significantly shortened in group C（P<0.05）.Compared with group D3,iCEB at T8 were significantly prolonged in groups C,D1 and D2（P<0.05）.ConclusionThe loading dose 0.5μg/kg and maintenance dose 0.5 μg·kg-1·h-1 of dexmedetomidine used in patients under general anesthesia can reduce abnormal electrocardiac action,maintain stability of cardiac electrophysiology,reduce the incidence of arrhythmia and has no significant adverse influences on cardiac output efficiency and hemodynamics during perioperative period. |
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