Sharma S K, McGuire G P, Cruise C J
Department of Anaesthesia, Toronto Hospital, University of Toronto, Ontario, Canada.
Can J Anaesth. 1995 Jun;42(6):498-503. doi: 10.1007/BF03011688.
This study was undertaken to examine the variation of the arterial to end-tidal PCO2 (Pa-PETCO2) difference during prolonged neurosurgical anaesthesia. Hyperventilation is often used to reduce intracranial pressure in neurosurgical patients. Continuous end-tidal CO2 monitoring is used as a guide between arterial CO2 measurements. We examined the stability of the Pa-PETCO2 difference in 21 patients undergoing elective craniotomies lasting greater than four hours. A balanced neuroanaesthetic technique was used with the ventilation variables at the discretion of the attending anaesthetist. Once patients were positioned for surgery, simultaneous samples of arterial PCO2 through an arterial catheter, and end-tidal PCO2 via a mass spectrometer were obtained. The Pa-PETCO2 differences of each patient were plotted against time and a slope was derived with simple linear regression. The mean slope for all patients was then computed. There were no changes in the Pa-PETCO2 difference with time (P > 0.05) suggesting a constant relationship between the arterial and end-tidal PCO2 measurements over time. We conclude that end-tidal PCO2 can be used as a reliable guide to estimate arterial PCO2 during neurosurgical procedures of greater than four hours duration once the Pa-PETCO2 difference has been established.
本研究旨在探讨长时间神经外科麻醉期间动脉血与呼气末二氧化碳分压（Pa-PETCO2）差值的变化。过度通气常用于降低神经外科患者的颅内压。持续呼气末二氧化碳监测用于指导动脉血二氧化碳测量之间的操作。我们检查了21例接受持续时间超过4小时的择期开颅手术患者的Pa-PETCO2差值的稳定性。采用平衡神经麻醉技术，通气变量由主治麻醉师酌情决定。患者一旦摆好手术体位，就通过动脉导管同时采集动脉血二氧化碳样本，并通过质谱仪获取呼气末二氧化碳值。将每位患者的Pa-PETCO2差值与时间作图，并通过简单线性回归得出斜率。然后计算所有患者的平均斜率。Pa-PETCO2差值随时间无变化（P>0.05），表明随着时间推移，动脉血与呼气末二氧化碳测量值之间存在恒定关系。我们得出结论，一旦确定了Pa-PETCO2差值，则在持续时间超过4小时的神经外科手术过程中，可以将呼气末二氧化碳用作估计动脉血二氧化碳的可靠指标。
