Department of Anesthesiology and Intensive Care Medicine, Helsinki University Central Hospital, Helsinki, Finland.
J Neurosurg Anesthesiol. 2010 Oct;22(4):303-8. doi: 10.1097/ANA.0b013e3181e33791.
Before obtaining results of arterial blood gas analysis in mechanically ventilated patients undergoing neurosurgery, the volume of ventilation is primarily adjusted according to endtidal CO2 (EtCO2). We characterized the impact of various arterial blood pressure changes on arterial PCO2 (PaCO2) to EtCO2 differences (PaCO2-EtCO2) in patients anesthetized for craniotomy.
Seventy-two elective craniotomy patients were enrolled in this prospective study. Noninvasive blood pressure was measured before anesthesia induction. Anesthesia was induced with thiopental, rocuronium or suxamethonium, and fentanyl and was maintained with inhaled anesthetics or propofol and remifentanil. Volume-controlled ventilation was adjusted after intubation according to the clinical judgment. The first arterial blood gas analysis was taken just before the head pinning. Systolic, diastolic, and mean arterial blood pressures (MAP) and heart rate were registered after intubation every 5 minutes until the head pinning.
PaCO2-EtCO2 correlated positively with percentage difference between MAP awake at arrival in operating room and during arterial CO2 determination (P=0.0008, r=0.388). In analysis according to a MAP decrease of less than 20% (n=17), 20% to 29% (n=24), 30% to 35% (n=16), and more than 35% (n=15), the mean (SD) PaCO2-EtCO2 was greater in patients with MAP decrease of over 35% or 30% to 35% than in patients with MAP decrease of less than 20%. The mean (SD) absolute values of the PaCO2-EtCO2 were 0.96 (0.43) kPa or 0.85 (0.31) kPa versus 0.55 (0.24) kPa, respectively (P<0.05 between categories). Mean EtCO2 was not different in the various MAP difference categories, but PaCO2 was greatest when MAP decreased more than 35% (P<0.05).
There was a positive correlation between PaCO2-EtCO2 and MAP decrease shortly after induction of anesthesia. PaCO2-EtCO2 is recommended to be interpreted together with change in MAP during early phase of neuroanesthesia to guarantee optimal mechanical ventilation.
在对接受神经外科机械通气的患者进行动脉血气分析之前，通气量主要根据呼气末二氧化碳（EtCO2）进行调整。我们描述了麻醉下接受颅切除术的患者中各种动脉血压变化对动脉 PCO2（PaCO2）与 EtCO2 差值（PaCO2-EtCO2）的影响。
本前瞻性研究纳入了 72 例择期行颅切除术的患者。在诱导麻醉前测量非侵入性血压。使用硫喷妥钠、罗库溴铵或琥珀胆碱诱导麻醉，并使用吸入麻醉剂或异丙酚和瑞芬太尼维持麻醉。插管后根据临床判断调整容量控制通气。第一次动脉血气分析在头钉固定前进行。记录插管后每 5 分钟的收缩压、舒张压和平均动脉压（MAP）和心率，直到头钉固定。
PaCO2-EtCO2 与 MAP 清醒时到达手术室时与动脉 CO2 测定时的百分比差异呈正相关（P=0.0008，r=0.388）。根据 MAP 降低<20%（n=17）、20%至 29%（n=24）、30%至 35%（n=16）和>35%（n=15）进行分析，MAP 降低>35%或 30%至 35%的患者的 PaCO2-EtCO2 均值（SD）大于 MAP 降低<20%的患者。MAP 降低>35%或 30%至 35%的患者的 PaCO2-EtCO2 均值（SD）绝对值分别为 0.96（0.43）kPa 或 0.85（0.31）kPa，而 MAP 降低<20%的患者分别为 0.55（0.24）kPa（P<0.05）。不同 MAP 差值类别的平均 EtCO2 无差异，但 MAP 降低超过 35%时 PaCO2 最大（P<0.05）。
麻醉诱导后不久，PaCO2-EtCO2 与 MAP 降低之间存在正相关。建议在神经麻醉早期将 PaCO2-EtCO2 与 MAP 变化一起解读，以保证最佳的机械通气。
