Effects Of Different Intraoperative End-tidal Carbon Dioxide Levels On Postoperative Nausea And Vomiting In Patients Undergoing Gynecological Laparoscopic Surgery

Objective:The incidence of postoperative nausea and vomiting（PONV）is high in patients undergoing laparoscopic gynecological surgery,and intraoperative Trendelenburg position and the use of CO₂ pneumoperitoneum are considered to increase the risk of PONV.It has been shown that intraoperative hypercapnia may increase blood perfusion to the brain and gastrointestinal tract and reduce the incidence of PONV by optimizing hemodynamics and tissue oxygenation.The partial pressure of arterial carbon dioxide（Pa CO₂）correlates well with end-tidal carbon dioxide（ETCO₂）levels.Therefore,in this study,we propose to investigate whether intraoperative ETCO₂ levels of different ranges affect the occurrence of PONV in patients undergoing gynecologic laparoscopic surgery.Methods:One hundred and twenty patients,who were to undergo gynecological laparoscopic surgery,aged 18 to 50 years,ASA class I to II,body mass index（BMI）18 to 24 kg/m~2,were randomly divided into three groups A,B,and C.ETCO₂ of 26 to 35 mm Hg（group A）,ETCO₂ of 36 to 45 mm Hg（group B）,and ETCO₂ of 46 to 55 mm Hg（group C）,with 40 patients in each group to be selected.After the patient was admitted to the operating room,routine vital signs monitoring was performed,and radial artery puncture and cannulation were performed under local anesthesia.All patients underwent ultrasound-guided posterior transversus abdominis plane block（TAPB）before induction of anesthesia.After confirming the success of the nerve block,all patients were given intravenous dexamethasone 5 mg followed by routine induction of anesthesia.Breathing was controlled after tracheal intubation with a tidal volume of 6-8 ml/kg,and the respiratory rate was adjusted to maintain the ETCO₂ range set within the three groups until the end of the procedure.Arterial blood gas analysis was performed in the three groups at 5 min after tracheal intubation and5 min after CO₂ pneumoperitoneum to determine the difference in partial pressure of CO₂ between Pa CO₂ and ETCO₂.All patients were given Flurbiprofen Axetil 50 mg intravenously at the end of the surgery,and no other postoperative medications were routinely given to prevent nausea and vomiting.After the surgery,the patient was transferred to the postanesthesia care unit（PACU）for continuous monitoring of vital signs and was transferred to the ward after meeting PACU departure criteria.Preoperative general information,hemodynamic parameters at the time of admission to the operating room（T0）,immediately after pneumoperitoneum（T1）,20 min after pneumoperitoneum（T2）,at the end of surgery（T3）,5 min after extubation（T4）,intraoperative fluid volume,anesthetic dosage,anesthesia time,surgery time,blood gas analysis,early（0-2 h after the operation）and delayed（2-24 h after the operation）nausea visual analogue scale（VAS）scores,the incidence of postoperative vomiting（POV）,PONV and use of rescue antiemetics,and occurrence of postoperative adverse events were recorded.Result（1）There was no statistically significant difference in the preoperative general information（including age,height,BMI,and ASA classification）among the three groups of patients（P>0.05）.（2）There were no statistically significant differences in intraoperative fluid volume,anesthetic dosage,anesthesia time,operation time and mean arterial pressure（MAP）,and heart rate（HR）at T0,T1,T2,T3,and T4 time points among the three groups of patients（P>0.05）;The differences in partial pressure of CO₂between Pa CO₂ and ETCO₂ at 5 min after tracheal intubation and 5 min after CO₂ pneumoperitoneum in the three groups were not statistically significant（P>0.05）.（3）The difference in nausea VAS scores from 0 to 2 h and 2 to 24 h after surgery was statistically significant in group B compared with group A（P<0.05）,and in group C compared with groups A and B（P<0.05）;For the comparison of the incidence of POV from 0 to 2 h and from 2 to 24 h after surgery,patients in group A had the highest incidence and group C had the lowest incidence,and the difference was statistically significant（P<0.05）.At 0 to 2 h,2 to 24 h,and 0 to24 h postoperatively,the highest proportion of patients in group A and the lowest proportion of patients in group C had PONV,with statistically significant differences（P<0.05）.After the operation,the proportion of patients using rescue antiemetics was highest in group A and lowest in group C.The difference was statistically significant（P<0.05）.（4）There was no statistically significant difference in the incidence of postoperative adverse events（including stridor,laryngospasm,breath-holding,hypoxia,chills,irritability,etc.）between the three groups of patients（P>0.05）.Conclusion:Intraoperative ETCO₂ levels in different ranges affect the incidence of PONV in patients undergoing gynecologic laparoscopic surgery,in which the incidence of PONV is lowest when ETCO₂ is maintained at 46-55 mm Hg and does not increase the incidence of postoperative adverse events.