Effects Of Cerebral Oxygen Saturation On Postoperative Nausea And Vomiting In Patients Undergoing Thyroid Surgery

Objective:To observe the relationship between regional cerebral oxygen saturation（rSO2）and postoperative nausea and vomiting in patients undergoing thyroid surgery,and to explore the effect of cerebral oxygen saturation on postoperative nausea and vomiting in such patients.Methods:A total of 70 female patients undergoing thyroid surgery under general anesthesia,aged 25-65 years,with a BMI 18.5-24kg/m²,lasting for more than 60minutes of operation time,falling into ASA physical status I or II category were randomly divided into two groups,mannitol group（group A,n=35）and control group（group C,n=35）.At the beginning of operation,20%mannitol 0.5g/kg was infused at the rate of 150 drops per minute in group A,and the same amount of normal saline was infused in group C at the same time.The general data of patients were recorded before operation,including ASA grade,age,BMI and preoperative hemoglobin level.During the operation,duration of the anesthesia and operation,the volume of intraoperative fluid infusion,the amount of rSO2,the mean arterial pressure,heart rate and urine volume at each time point were recorded,including the time when the patient entered the room（T1）,the time after tracheal intubation（T2）,the time immediately after cervical hyperextension（T3）,the time immediately after the operation（T4）,the time 40 minutes after the operation（T5）,at the end of operation（T6）.The incidence of postoperative nausea and vomiting in each group was followed up within 48 hours.Results:There was no significant difference in ASA grade,age,BMI,preoperative hemoglobin level,duration of the anesthesia and operation,fluid infusion between the two groups（P>0.05）.At T₁,T₂,T₃ and T₄,there was no significant difference in urine volume between the two groups（P>0.05）.At T5 and T6,the urine volume of group A was significantly higher than that of group C（P<0.05）.There was no significant difference in the mean arterial pressure and heart rate between the two groups at every point in time（P>0.05）.Compared with T₁,T₃,T₄,T₅ and T₆,the rSO₂ of the two groups increased at T₂（P<0.05）.Compared with T₃ and T₄ in group C,rSO₂ was significantly lower at T₅ and T₆（P<0.05）.Compared with T₃ and T₄ in group A,there was no significant decrease in rSO2 at T5 and T6（P>0.05）.Compared with group C,the level of rSO₂ in group A was significantly higher at T₅ and T₆（P<0.05）.The incidence of postoperative nausea and vomiting in group A was significantly lower than that in group C（28.6%vs 57.1%）（P<0.05）,and the severity of postoperative nausea and vomiting in group C was higher than that in group A（P<0.05）.Conclusion:Preoperative intravenous infusion of low dose（0.5g/kg）mannitol can improve the regional cerebral oxygen saturation and reduce the incidence and severity of postoperative nausea and vomiting.