Clinical Observation Of Individualized Small Tidal Volume Low-frequency Ventilation Based On P_ETCO₂ For Transurethral Ureteroscopic Lithotripsy

Objective:To investigate the effect of an individualized small tidal volume low-frequency ventilation strategy based on the end-expiratory partial pressure of carbon dioxide(P_ETCO₂)on patients undergoing transurethral ureteroscopic lithotripsy（URL）.Methods:Ninety patients proposed for daytime transurethral ureteroscopic lithotripsy under general anesthesia with endotracheal intubation,of any gender,aged 25-60 years,with BMI 18-27.9 kg/m2 and ASA class I or II,were selected and divided into three groups using the random number table method:the conventional control group（group C,n=30）,the apnea group（group A,n=30）,and the individualized small-tidal-volume low-frequency group（group I,n=30）.The same anesthetic induction and anesthetic maintenance drugs were used in all three groups.Group C continued to use V_T 8 ml/kg and RR 12 times/min when the surgeon signaled lithotripsy,group A used intermittent apnea ventilation mode with a maximum of 5 min for a single apnea,and Group I used individualized small tidal volume（V_T 4～6 ml/kg）low frequency（RR 6～8 times/min）ventilation mode oriented to P_ETCO₂.HR,MAP,Sp O2,BIS were observed and recorded in the three groups at five time points before induction of anesthesia（T₀）,10minutes after tracheal intubation（T₁）,at the beginning of lithotripsy（T₂）,immediately after the end of lithotripsy（T₃）,and 30 min after removal of the tracheal tube（T₄）.Respiratory-related indexes were recorded:P_ETCO₂,Ppeak,Pplat at T_1-3,PH,Pa O₂,Pa CO₂ at T₃;surgery-related indexes were recorded:maximum stone diameter,CT value,laser lithotripsy time,operation time,operator satisfaction score;postoperative extubation time,orientation recovery time were recorded.Results:Compared with group C,P_ETCO₂ was significantly higher in group A at T₃（P<0.05）,Pplat and Ppeak were significantly lower in group I at T_2-3（P<0.05）,PH,Pa O₂ were significantly lower and Pa CO₂ was significantly higher in group A at T₃（P<0.05）;compared with group A,Pplat and Ppeak were significantly lower in group I at T_2-3（P<0.05）,PH and Pa O₂ were significantly higher at T₃（P<0.05）,P_ETCO₂ and Pa CO₂were significantly lower at T₃（P<0.05）.Compared with group C,intraoperative lithotripsy time and operative time were significantly shorter in groups A and I,and the operator satisfaction score was significantly higher in groups A and I（P<0.05）;compared with group A,intraoperative lithotripsy time and The operating time was significantly shortened in group I（P<0.05）,and the operator satisfaction score were not statistically significant in group I（P>0.05）.P_ETCO₂ and Pa CO₂were positively correlated in the three groups at T₃（r=0.7581,P<0.05）.The differences in HR,MAP,Sp O₂ and BIS were not statistically significant in the three groups（P>0.05）;the differences in the maximum diameter of stones and CT values were not statistically significant in the three groups（P>0.05）;the differences in extraction time and recovery time of orientation were not statistically significant in the three groups（P>0.05）.Conclusion:The individualized small tidal volume low-frequency ventilation strategy based on P_ETCO₂ can be used safely and efficiently for daytime URL patients and is a more optimal ventilation strategy.