From the Department of Anaesthesiology, Hospital Clínic de Barcelona, University of Barcelona (JT, IG, PH, NdR, EC, MG-O, IB, NF, RV), Institut d'Investigacions Biomédiques August Pi i Sunyer (IDIBAPS) and Centro de Investigación Biomédica en Red de Salud Mental (CIBERSAM) (RV), Medical Statistics Core Facility, IDIBAPS and Hospital Clinic de Barcelona (JR), Biostatistics Unit, Faculty of Medicine, Universitat Autònoma de Barcelona, Barcelona, Spain (JR) and Department of Anaesthesiology, Faculty of Medicine, Hospital Clínico Universidad de Chile, University of Chile, Santiago, Chile (FM).
Eur J Anaesthesiol. 2021 Jan;38(1):49-57. doi: 10.1097/EJA.0000000000001356.
Maintaining adequate blood pressure to ensure proper cerebral blood flow (CBF) during surgery is challenging. Induced mild hypotension, sitting position or unavoidable intra-operative circumstances such as haemorrhage, added to variations in carbon dioxide and oxygen tensions, may influence perfusion. Several of these circumstances may coincide and it is unclear how these may affect CBF.
To describe the variation in transcranial Doppler and regional cerebral oxygen saturation (rSO2), as a surrogate of CBF, after cardiac preload and gravitational positional changes.
Observational study.
Operating room at Hospital Clínic de Barcelona.
Ten healthy volunteers, white, both sexes.
Measurements were performed in the supine, sitting and standing positions during hyperoxia, hypocapnia and hypercapnia protocols and after a Valsalva manoeuvre.
Cardiac index (CI), haemodynamic and respiratory variables, maximal and mean velocities (Vmax, Vmean) (transcranial Doppler) and rSO2 were acquired. Results were analysed using a generalised estimating equation technique.
CI increases more than 16% after a preload challenge were not accompanied by differences in rSO2 or Vmax - Vmean. With positional changes, Vmean decreased more than 7% (P = 0.042) from the supine to the seated position. Hyperoxia induced a cerebral rSO2 increase more than 6% (P = 0.0001) with decreases in Vmax, Vmean and CI values more than 3% (P = 0.001, 0.022 and 0.001) in the supine and standing position. During hypocapnia, CI rose more than 20% from supine to seated and standing (P = 0.0001) with a 4.5% decrease in cerebral rSO2 (P = 0.001) and a decrease of Vmax - Vmean more than 24% in all positions (P = 0.001). Hypercapnia increased cerebral rSO2 more than 17% (P = 0.001), Vmax - Vmean more than 30% (P = 0.001) with no changes in CI. After a Valsalva manoeuvre, rSO2 decreased more than 3% in the right hemisphere in the upright position (P = 0.001). Vmax - Vmean decreased more than 10% (P = 0.001) with no changes in CI.
CBF changes in response to cerebral vasoconstriction and vasodilatation were detected with rSO2 and transcranial Doppler in healthy volunteers during cardiac preload and in different body positions. Acute hypercapnia had a greater effect on recorded brain parameters than hypocapnia.
在手术过程中维持足够的血压以确保适当的脑血流（CBF）是具有挑战性的。诱导轻度低血压、坐姿或术中不可避免的情况（如出血），加上二氧化碳和氧气张力的变化，可能会影响灌注。这些情况中的一些可能同时发生，目前尚不清楚这些情况可能如何影响 CBF。
描述心脏前负荷和重力位置变化后经颅多普勒和局部脑氧饱和度（rSO2）的变化，rSO2 是 CBF 的替代指标。
观察性研究。
巴塞罗那 Clinic 医院手术室。
10 名健康志愿者，白种人，男女不限。
在过度通气、低碳酸血症和高碳酸血症方案以及瓦尔萨尔瓦动作后，在仰卧位、坐位和站立位进行测量。
心指数（CI）、血流动力学和呼吸变量、最大和平均速度（Vmax、Vmean）（经颅多普勒）和 rSO2。使用广义估计方程技术分析结果。
心脏前负荷挑战后 CI 增加超过 16%，但 rSO2 或 Vmax-Vmean 没有差异。体位变化时，从仰卧位到坐位 Vmean 下降超过 7%（P=0.042）。高氧诱导 rSO2 增加超过 6%（P=0.0001），仰卧位和站立位 Vmax、Vmean 和 CI 值下降超过 3%（P=0.001、0.022 和 0.001）。在低碳酸血症期间，CI 从仰卧位增加超过 20%至坐位和站立位（P=0.0001），脑 rSO2 下降 4.5%（P=0.001），所有体位 Vmax-Vmean 下降超过 24%（P=0.001）。高碳酸血症使 rSO2 增加超过 17%（P=0.001），Vmax-Vmean 增加超过 30%（P=0.001），CI 无变化。瓦尔萨尔瓦动作后，右半球 rSO2 在直立位下降超过 3%（P=0.001）。Vmax-Vmean 下降超过 10%（P=0.001），CI 无变化。
在心脏前负荷和不同体位下，健康志愿者 rSO2 和经颅多普勒检测到脑血流对脑血管收缩和扩张的反应变化。急性高碳酸血症对记录的脑参数的影响大于低碳酸血症。
