Department of Physiology and Pharmacology, Faculty of Medicine, University of Salamanca, Salamanca, Spain.
Department of Anesthesiology, Centro Hospitalar do Baixo Vouga.
J Neurosurg Anesthesiol. 2020 Apr;32(2):147-155. doi: 10.1097/ANA.0000000000000572.
Induction of anesthesia and the knee-chest position are associated with hemodynamic changes that may impact patient outcomes. The aim of this study was to assess whether planned reductions in target-controlled infusion propofol concentrations attenuate the hemodynamic changes associated with anesthesia induction and knee-chest position.
A total of 20 patients scheduled for elective lumbar spinal surgery in the knee-chest position were included. In addition to standard anesthesia monitoring, bispectral index and noninvasive cardiac output (CO) monitoring were undertaken. The study was carried out in 2 parts. In phase 1, target-controlled infusion propofol anesthesia was adjusted to maintain BIS 40 to 60. In phase 2, there were 2 planned reductions in propofol target concentration: (1) immediately after loss of consciousness-reduction calculated using a predefined formula, and (2) before positioning-reduction equal to the average percentage decrease in CO after knee-chest position in phase 1. Changes from baseline in CO and other hemodynamic variables following induction of anesthesia and knee-chest positioning were compared.
Induction of anesthesia led to decreases of 25.6% and 19.8% in CO from baseline in phases 1 and 2, respectively (P<0.01). Knee-chest positioning resulted in a further decrease such that the total in CO reduction from baseline to 10 minutes after positioning was 38.4% and 46.9% in phases 1 and 2, respectively (P<0.01). There was no difference in CO changes between phases 1 and 2, despite the planned reductions in propofol during phase 2. There was no significant correlation between changes in CO and mean arterial pressure.
Planned reductions in propofol concentration do not attenuate anesthesia induction and knee-chest position-related decreases in CO. The knee-chest position is an independent risk factor for decrease in CO. Minimally invasive CO monitors may aid in the detection of clinically relevant hemodynamic changes and guide management in anesthetized patients in the knee-chest position.
麻醉诱导和膝胸位会引起血流动力学变化，可能会影响患者的结局。本研究旨在评估目标控制输注丙泊酚浓度的计划性降低是否能减轻麻醉诱导和膝胸位相关的血流动力学变化。
共纳入 20 例行膝胸位择期腰椎手术的患者。除了标准的麻醉监测外，还进行了脑电双频指数和无创心输出量（CO）监测。该研究分两部分进行。在第 1 部分中，调整目标控制输注丙泊酚麻醉以维持 BIS 40 至 60。在第 2 部分中，有 2 次计划降低丙泊酚靶浓度：（1）意识丧失后立即降低-使用预定义公式计算；（2）定位前降低-等于第 1 部分膝胸位后 CO 的平均百分比降低。比较麻醉诱导和膝胸位后 CO 和其他血流动力学变量与基线的变化。
麻醉诱导导致 CO 分别比基线下降 25.6%和 19.8%（P<0.01）。膝胸位导致进一步下降，以至于定位后 10 分钟时 CO 与基线相比的总降低率分别为 1 期和 2 期的 38.4%和 46.9%（P<0.01）。尽管第 2 部分计划降低丙泊酚浓度，但 CO 变化在 1 期和 2 期之间没有差异。CO 变化与平均动脉压之间无显著相关性。
丙泊酚浓度的计划性降低不能减轻麻醉诱导和膝胸位相关的 CO 下降。膝胸位是 CO 下降的独立危险因素。微创 CO 监测器可能有助于检测临床相关的血流动力学变化，并指导膝胸位麻醉患者的管理。
