Department of Anaesthesiology.
Department of Medical Biology, Laboratory for Clinical Cardiovascular Physiology.
Br J Anaesth. 2017 Dec 1;119(6):1141-1149. doi: 10.1093/bja/aex333.
Cerebral autoregulation (CA) is the mechanism that maintains constancy of cerebral blood flow (CBF) despite variations in blood pressure (BP). Patients with attenuated CA have been shown to have an increased incidence of peri-operative stroke. Studies of CA in anaesthetized subjects are rare, because a simple and non-invasive method to quantify the integrity of CA is not available. In this study, we set out to improve non-invasive quantification of CA during surgery. For this purpose, we introduce a novel method to amplify spontaneous BP fluctuations during surgery by imposing mechanical positive pressure ventilation at three different frequencies and quantify CA from the resulting BP oscillations.
Fourteen patients undergoing sevoflurane anaesthesia were included in the study. Continuous non-invasive BP and transcranial Doppler-derived CBF velocity (CBF V ) were obtained before surgery during 3 min of paced breathing at 6, 10, and 15 bpm and during surgery from mechanical positive pressure ventilation at identical frequencies. Data were analysed using frequency domain analysis to obtain CBF V -to-BP phase lead as a continuous measure of CA efficacy. Group averages were calculated. Values are means ( sd ), and P <0.05 was used to indicate statistical significance.
Preoperative vs intraoperative CBF V -to-BP phase lead was 43 (9) vs 45 (8)°, 25 (8) vs 24 (10)°, and 4 (6) vs -2 (12)° during 6, 10, and 15 bpm, respectively (all P =NS).
During surgery, cerebral autoregulation indices were similar to values determined before surgery. This indicates that CA can be quantified reliably and non-invasively using this novel method and confirms earlier evidence that CA is unaffected by sevoflurane anaesthesia.
NCT03071432.
脑自动调节（CA）是一种机制，它可以在血压（BP）变化的情况下维持脑血流（CBF）的恒定性。已经证明，CA 减弱的患者围手术期中风的发生率增加。由于缺乏简单且非侵入性的方法来量化 CA 的完整性，因此在麻醉患者中进行 CA 研究很少见。在这项研究中，我们旨在改进手术期间 CA 的非侵入性量化。为此，我们提出了一种新方法，通过在三个不同频率下施加机械正压通气来放大手术期间的自发性 BP 波动，并从由此产生的 BP 振荡中量化 CA。
本研究纳入了 14 名接受七氟醚麻醉的患者。在手术前，患者接受了 3 分钟的 paced breathing，频率分别为 6、10 和 15 bpm，然后在手术期间接受相同频率的机械正压通气，连续获得非侵入性 BP 和经颅多普勒衍生的 CBF 速度（CBF V ）。使用频域分析来获得 CBF V 到 BP 的相位领先作为 CA 功效的连续测量。计算组平均值。值表示为平均值（标准差），P <0.05 表示具有统计学意义。
术前与术中 CBF V 到 BP 的相位领先分别为 43°（9°）和 45°（8°）、25°（8°）和 24°（10°）以及 4°（6°）和-2°（12°），分别在 6、10 和 15 bpm 时（所有 P =NS）。
在手术期间，CA 指数与术前值相似。这表明可以使用这种新方法可靠且非侵入性地量化 CA，并证实了早期的证据，即 CA 不受七氟醚麻醉的影响。
NCT03071432。
