The Effects Of Different Doses Of Dexmedetomidine On Postoperative Nausea And Vomiting After Neuro-monitoring Thyroid Surgery

ObjectivePostoperative nausea and vomiting（PONV）is a common complication after anesthesia,which often leads to dehydration,electrolyte disorder,wound dehiscence and other adverse consequences.In recent years,with the diagnosis rate of thyroid disease increasing year by year,thyroid surgery is becoming more and more common.Intraoperative neuromonitoring（IONM）has become an important method to determine recurrent laryngeal nerve function and prevent recurrent laryngeal nerve injury during thyroid surgery.IONM technology presents new challenges for anesthesiologists,requiring us to reduce the use of muscle relaxation drugs while ensuring appropriate sedation and analgesia,so as not to affect the acquisition of EMG signals.However,postoperative patients often suffer from nausea and vomiting and other adverse reactions.Dexmedetomidine（Dex）is a potentα2 adrenergic receptor agonist widely used because of its sedative,analgesic,anti-anxiety,anti-sympathetic and blood regulation functions.More and more studies have shown that low-dose Dex can also reduce the incidence of postoperative nausea and vomiting.In this paper,the effects of dexmedetomidine on postoperative thyroid nausea and vomiting under neurological monitoring and its optimal preventive dose were investigated,and intraoperative hemodynamics,intraoperative medication and postoperative adverse reactions were analyzed and compared.Methods160 patients undergoing elective thyroid surgery in our hospital were randomly divided into 4 groups:control group（group C）,dexmedetomidine 0.2ug/kg/h group（DEX1 group）,0.4ug/kg/h group（DEX2 group）and 0.6ug/kg/h group（DEX3 group）.After the patient entered the room,the vein was opened,the monitor was connected,and the mean arterial pressure and heart rate were determined as the base values.Propofol（2mg/kg）,sufentanil（0.4ug/kg）and cineataquurium（0.05mg/kg）were used for induction.After induction,normal saline or dexmedetomidine at the target concentration was pumped continuously by micro pump until half an hour before the end of surgery.Pet-CO₂was maintained between 35 and 45mm Hg by adjusting VT,RR and I:E.Intraoperatively,sevoflurane（1.5-2.5%）（end-expiratory concentration）was anesthetized with 50%oxygen and air.The concentration of sevoflurane was adjusted based on BIS and hemodynamics to maintain bis values between 40 and 60.Remifentanil was continuously injected（0.1-0.2 mg/kg/min）,and the pumping rate of remifentanil was adjusted according to the changes of MAP and HR.All patients were given lactate Ringer solution 4～8 m L/kg·h supplement fluid.In addition,colloids were used instead of blood loss.Dexmedetomidine was stopped 30 minutes before the end of surgery.Sevoflurane tank was closed and inhalation of sevoflurane was stopped.Remifentanil was stopped at the end of sevoflurane and the residual sevoflurane was replaced and discharged with 3-4L/min of fresh pure oxygen until the patient woke up naturally.ResultsThe incidence of nausea within 2 hours after surgery in dexmedetomidine 0.6ug/kg/h group was lower than that in the control group[27.5%（11/40）vs.57.5%（23/40）,P=0.007],and the overall incidence of PONV within 2 hours after surgery in Dex group was lower than that in the control group,the difference was statistically significant（P=0.014）.Gender,smoking history,history of motion sickness and postoperative nausea and vomiting were risk factors for PONV.ConclusionsFor adult patients undergoing thyroid surgery,continuous pumping dexmedetomidine during general anesthesia can reduce the incidence of early postoperative nausea,and 0.6ug/kg/h continuous pumping is recommended.