The Effects Of Conscious Sedation With Dexmedetomidine During The Radiofrequency Ablation Of The Thyroid Gland

BackgroundWith the development of minimally invasive surgery,more and more patients chose the radiofrequency ablation which has the advantages of less trauma,faster recovery and less complications to treat the benign thyroid nodules.Though the procedure is mild invasive,the patient's anxiety and nervousness nearly do not decrease,which may produce a negative influence on the surgeon and do some disadvantage effect to the procedure.Monitored anesthesia care and sedation can effectively relieve the nervous and fear of the patients,ease the pain and inhibit some negative stress response of the body.the effect of conscious sedation is between the general anesthesia and local anesthesia.At this level of sedation,the patient is able to make a purposeful response to verbal or light touch stimulation and both ventilatory and cardiovascular function are maintained.It can also reduce the incidence of nerve injury and improve the comfort of the patients and facilitate surgical procedures.The target of the sedation agents is cooperative,anxiolytic and amnestic,these are the desired level to minimally invasive surgery.The theory of using the radiofrequency ablation in the treatment of thyroid nodules is inserting the needle into the nodules under the guiding of ultrasound.Then the high frequency alternating current generated by the electrode generate the RF wave,which cause the polar molecules and ions to vibrate rapidly and rub each other,resulting in the electric energy converted into heat energy.Subsequently,the local nodule tissue is frozen and necrotic due to high temperature,and finally the nodules are inactivated.Recently due to its minimally invasive properties,fast recovery and less complications,more and more patients chose the radiofrequency ablation to treat thyroid nodules.Dexmedetomidine is a potent,highly selective ?? adrenoceptor agonist with a 1620:1 ratio of ?? to ??.The hypnotic effect of dexmedetomidine is mediated by the hyperpolarization of noradrenergic neurons in the locus ceruleus of the brain stem,which is the primary site in modulating wakefulness.Dexmedetomidine produces sedation without significant respiratory depression,and allows patients to respond purposefully to verbal commands and light touch stimulation,but may drift off to sleep in between periods of stimulation.It can inhibit the release of norepinephrine and enhance the activity of vagus nerve,which causes reduction in blood pressure and heart rate.It has also been shown to have sedative,analgesic,and anxiolytic effects when given intravenously to healthy volunteers,and has produced stable sedation in patients ventilated postoperatively while the patient remained rousable and are less anxious.It produces dose-dependent sedation,anxiolysis,and analgesia without respiratory depression.Infusion of a small dose of the drug in healthy volunteers provided sedation that could easily be reversed with verbal stimulation.Dexmedetomidine may prove to be a better sedative drug for minimally invasive surgery sedation than midazolam because of its analgesic property,shorter recovery profile,and less cognitive impairment and respiratory depression.This study was designed to study the efficacy(sedation,anxiolysis,analgesia,operating conditions,and patients' satisfaction)and safety of dexmedetomidine as sedatives for the radiofrequency ablation of the thyroid gland.So as to provide a theoretical basis for the clinical use of drugs.MethodA total of 88 ASA physical status ? or ? patients undergoing the radiofrequency ablation of the thyroid gland with monitored anesthesia care in our hospital were selected.Seventy-three females and fifteen males.Patients with Ventilation dysfunction,mental disorders,severe liver and renal insufficiency and those who are allergic to drugs that used in the study were excluded.the cases were divided into 4 groups using the random number method.each group contains 22 patients.After entered the operation room the patients were given riger's solution 5 ml/(kg·h),standard monitorization(electrocardiogram(ECG),heart rate(HT),pulse oxymetry(SPO2)and noninvasive blood pressure(INBP)with 3-min intervals)and bispectral index(BIS)were recorded and these parameters were continuously monitored throughout the study period.in group A,a bolus dose of 0.5?g/kg dexmedetomidine was infused intravenously over 10 min starting 10 min before the procedure.in group B,a bolus dose of 1.0?g/kg dexmedetomidine was infused intravenously over 10 min starting 10 min before the procedure.in group C,a bolus dose of 100 cc normal saline was infused intravenously over 10 min starting 10 min before the procedure.in group D,a bolus dose of 0.04mg/kg midazolam was infused intravenously over 10 min starting 10 min before the procedure.we collected BIS,mean arterial pressure(MAP),HR and SPO2 figures of both groups at entered the operation room time(T0),when 1min after the delivery(T1),5min(T2),10min(T3),20min(T4),30min(T5),60min(T6).their degree of satisfaction,the discharged time,OAA/S,duration of operation and the adverse events.Result1.Baseline characteristics were similar for all patients between the three groups in age,weight,sex,ASA classification(P> 0.05).2.Compared to the time point of T0,the MAP and HR at the time point of T2~T6 in DH group were significantly decreased(P<0.05).When compared with the group DL,S and M,the MAP and HR at the time point of T2~T6 in DH group were also significantly decreased(P<0.05).Compared to the time point of T0,the MAP and HR at the time point of T2~T6 in DL and M groups were some changes,but the deference was no statistically significant differences(P> 0.05).3.The incidence of mild respiratory depression(SPO2<95%)in group M were significantly increased when compared with the others groups(P<0.05).4.Compared to the time point of T0,the BIS at the time point of T2~T6 in DL,DH and M group were significantly decreased(P<0.05).5.Compared with the group M and S,the patients cooperation and surgeon satisfaction score of the group DL and DH were significantly high(P<0.05).ConclusionsCompared with midazolam,dexmedetomidine could be used appropriately for MAC in radiofrequency ablation surgery with better satisfaction from the surgeons and a more stable cardiovascular state.