The Effects Of Femoral Nerve Block Guided By Ultrasound On The MAC_BAR Of Sevoflurane In Patients Undergoing Knee Arthroscopy Surgery

Objective:To compare the effect of femoral nerve block guided by ultrasound on the MACBAR of sevoflurane in patients undergoing knee arthroscopy with arthroscopy stimulus.In addition to observing the changes of plasma adrenaline and norepinephrine concentrations before and after knee arthroscopy stimulus.Methods:From May 2019 to August 2019,50 patients who undergoing unilateral knee arthroscopy in our hospital were selected and randomly divided into two groups:one for the control group with only general anesthesia,and the other for the experimental group with femoral nerve block plus general anesthesia,25 patients in each group.Patients in the experimental group were treated with ultrasound-guided femoral nerve block and the effect of femoral nerve block was confirmed before induction of intravenous anesthesia.Patients in the two groups were treated with unified standard intravenous anesthesia induction,tracheal intubation and mechanical ventilation.After intubation,all patients in each group inhaled sevoflurane,and the preset end tidal sevoflurane concentration was maintained stable at least for 15 minutes before knee arthroscopy stimulus.The hemodynamic changes were observed before and after the knee arthroscopy stimulus.The MACBAR of sevoflurane was measured by a sequential method,and the radial arterial blood samples were taken before and after the knee arthroscopy stimulus for determining the plasma norepinephrine and epinephrine concentrations.Results:The MACBAR of sevoflurane in the control group(3.50±0.29)%was significantly higher than that in the experimental group(2.73±0.13)%,P<0.05.No statistically significant differences were found in the changes of adrenaline and norepinephrine concentrations in the blood when half patients’ adrenergic responses were inhibited in each group.Conclusion:Ultrasound-guided femoral nerve block can effectively reduce the MACBAR of sevoflurane for 22%in patients undergoing knee arthroscopic surgery.No significant changes of epinephrine and norepinephrine concentrations were found in the plasma when the stress response of patients was suppressed to a same extent.