Application Of Methoxamine In Patients With Hypertension Undergoing Lumbar Surgery In Prone Position

Objective:The main purpose of this study was to investigate whether continuous intravenous injection of methoxamine could reduce the incidence of hypotension and maintain stable hemodynamics in patients with hypertension under general anesthesia in prone position for lumbar spine surgery,and provide some references for clinical anesthesia.Methods:Forty patients with hypertension undergoing lumber PLIF surgery under general anesthesia were randomly divided into two groups:control group?n=20?and trial group?n=20?.After entering the operating room,vital signs including electrocardiogram,non-invasive blood pressure,SpO₂,BIS were routinely monitored.Radial artery puncture was performed under local anesthesia,and invasive arterial blood pressure was continuously monitored.The patients in both groups were given 5ml/kg lactate Ringer injection before anesthesia and endotracheal intubation was performed 2 minutes after induction with midazolam 0.03 mg/kg,sufentanil 0.5 mg/kg,rocuronium 0.8 mg/kg and etomidate 0.3mg/kg.Volume controlled ventilation mode was used to maintain the P_ETCO₂ at 35⁴5mmHg.The body was slowly turned over to the prone position after the hemodynamics was stable and continuous intravenous infusion of propofol and remifentanil were used to maintain anesthesia.After prone position,methoxamine was continuous intravenous injected by 1.5²?g·kg^-1·min^-11 for 30 min in the patients of trial group.In the control group,6mg ephedrine was given intravenously if the patients'systolic blood pressure was lower than 100mmHg after prone position.The fluid was rehydrated at the speed of 5ml·kg^-1·h^-11 during the operation.The depth of anesthesia was adjusted according to the surgical stimulation,and the BIS value was maintained between 40 and 60.Atropine 0.5mg was given if the heart rate was less than 50 bpm.The blood pressure and heart rate of the two groups were recorded at the following 12 time points,including before induction?T0?,2 minutes after induction?T1?,before prone position?T2?,after prone position?T3?,5 minutes after prone position?T4?,10 minutes after prone position?T5?,15 minutes after prone position?T6?,20 minutes after prone position?T7?,25 minutes after prone position?T8?,30 minutes after prone position?T9?,45 minutes after prone position?T10?and 60 minutes after prone position?T11?.The number and total amount of ephedrine and atropine used in the two groups were recorded.The total amount of propofol,remifentanil,fluid rehydration,blood loss and urine volume were summarized at the end of the experiment.Adverse events such as severe hypotension?SBP<80mmHg?,hypertension?SBP>180mmHg?,arrhythmia were recorded.Results:There was no significant difference in general data between the two groups.Compared with pre-anesthesia,MBP and HR of the two groups were decreased significantly after prone position.Compared with the blood pressure at 5 minutes after prone position,the blood pressure in the control group decreased significantly at 10³0minutes after prone position,but in the trial group there was no significant difference in blood pressure at the time of 10,20 and 30 minutes and the blood pressure dropped slightly at the time of 15,25,45 and 60 minutes after prone position.Compared with the control group,the blood pressure in the trial group was significantly higher at the time of10 and 20⁴5minutes after prone position.There was no significant difference in HR between the two groups.There was no significant difference in the drug dosage of anesthetic,as well as the volume of fluid rehydration,blood loss and urine volume.210mg ephedrine was used in the control group,while 6mg ephedrine was used in the trial group.Neither group was given atropine during the surgery.No serious hypotension?SBP<80mmHg?,hypertension?SBP>180mmHg?,arrhythmia and other adverse events occurred during anesthesia.Conclusion:Hypotension is easy to occur in patients with hypertension undergoing lumbar PLIF operation in prone position under general anesthesia.Both intermittent intravenous injection ephedrine and continuous intravenous injection methoxamine after prone position with proper volume supplement can increase blood pressure.But continuous intravenous injection of 1.5²?g·kg^-1·min^-11 methoxamine for 30 minutes after prone position can effectively reduce the occurrence of hypotension in prone position,maintain stable hemodynamics during operation,and have no significant effect on heart rate.