Factors Influencing Regional Cerebral Oxygen Saturation during One-lung Ventilation in Thoracic Surgery

Objective To identify factors influencing regional cerebral oxygen saturation (rScO₂) during one-lung ventilation (OLV) in thoracic surgery. Methods Totally 33 patients with an ASA physical status of 1-3 scheduled for elective thoracic surgery with one-lung ventilation under general anesthesia were recruited. After anesthesia was induced with propofol,fentanyl/sufentanil,and rocuronium. All patients received balanced anesthesia using sevoflurane. During OLV,volume-controlled ventilation was used with a tidal volume of 6-7 ml/kg and an inspiration:expiration ratio of 1:1.5. The ventilator frequency was adjusted with a target end-tidal carbon dioxide partial pressure (PetCO₂) between 35 mmHg and 45 mmHg. During the anesthesia,patients were maintained at a pulse oxygen saturation (SpO₂) of>90%,systolic blood pressure (SBP) of>90 mmHg (or reducing no more than 30% of the basic values),heart rate (HR) of>50 beat/min,and hemoglobin concentration of>90 g/L. Changes of rScO₂ were monitored with FORESIGHT probes by specialized researchers. Patients were classified into low rScO₂ (L-rScO₂) group (n=10) or high rScO₂ (H-rScO₂)group(n=23) according to whether the lowest intraoperative rScO₂ was under 65% or 15% lower than the baseline values. We compared gender,age,body mass index (BMI),intraoperative hemoglobin level,and the values of peak airway pressure (Ppeak),SBP,PetCO₂,and SpO₂ when rScO₂ dropped to the lowest level between these two groups. Results Statistically higher Ppeak and lower SBP were noted in the L-rScO₂ group compared with H-rScO₂ group (P=0.028,P=0.046). SpO₂ was lower in the L-rScO₂ group compared with H-rScO₂ group,but the difference was not statistically significant (P=0.421). There was also no significant difference between the two groups according to age,BMI,SpO₂,PetCO₂,or hemoglobin level. Ppeak appeared to be a risk factor for rScO₂ reduction during OLV,as shown by unconditioned Logistic regression analysis. Conclusion During OLV in thoracic surgery,Ppeak is a risk factor for rScO₂ reduction.