Department of Biomedical Sciences for Health, Galeazzi Orthopedic Institute, University of Milan, Milan, Italy;
J Appl Physiol (1985). 2013 Oct 1;115(7):1032-42. doi: 10.1152/japplphysiol.00537.2013. Epub 2013 Jul 18.
Cardiac baroreflex is a fundamental component of the cardiovascular control. The continuous assessment of baroreflex sensitivity (BRS) from spontaneous heart period (HP) and systolic arterial pressure (SAP) variations during general anesthesia provides relevant information about cardiovascular regulation in physiological conditions. Unfortunately, several difficulties including unknown HP-SAP causal relations, negligible SAP changes, small BRS values, and confounding influences due to mechanical ventilation prevent BRS monitoring from HP and SAP variabilities during general anesthesia. We applied a model-based causal closed-loop approach aiming at BRS assessment during propofol anesthesia in 34 patients undergoing coronary artery bypass graft (CABG) surgery. We found the following: 1) traditional time and frequency domain approaches (i.e., baroreflex sequence, cross-correlation, spectral, and transfer function techniques) exhibited irremediable methodological limitations preventing the assessment of the BRS decrease during propofol anesthesia; 2) Granger causality approach proved that the methodological caveats were linked to the decreased presence of bidirectional closed-loop HP-SAP interactions and to the increased incidence of the HP-SAP uncoupling; 3) our model-based closed-loop approach detected the significant BRS decrease during propofol anesthesia as a likely result of accounting for the influences of mechanical ventilation and causal HP-SAP interactions; and 4) the model-based closed-loop approach found also a diminished gain of the relation from HP to SAP linked to vasodilatation and reduced ventricular contractility during propofol anesthesia. The proposed model-based causal closed-loop approach is more effective than traditional approaches in monitoring cardiovascular control during propofol anesthesia and indicates an overall depression of the HP-SAP closed-loop regulation.
心脏压力反射是心血管控制的基本组成部分。在全身麻醉期间，从自发的心率 (HP) 和收缩压 (SAP) 变化中连续评估压力感受反射敏感性 (BRS)，可提供有关生理条件下心血管调节的相关信息。不幸的是，由于机械通气的影响，包括 HP-SAP 因果关系未知、SAP 变化可忽略不计、BRS 值较小以及混杂影响等多种困难，使得在全身麻醉期间无法从 HP 和 SAP 变异性监测 BRS。我们应用了基于模型的因果闭环方法，旨在评估 34 例行冠状动脉旁路移植术 (CABG) 患者的丙泊酚麻醉期间的 BRS。我们发现：1）传统的时频域方法（即压力反射序列、互相关、频谱和传递函数技术）表现出不可弥补的方法学局限性，无法评估丙泊酚麻醉期间 BRS 的降低；2）格兰杰因果关系方法证明，方法上的缺陷与双向闭环 HP-SAP 相互作用的减少以及 HP-SAP 解耦的发生率增加有关；3）我们基于模型的闭环方法检测到丙泊酚麻醉期间 BRS 的显著降低，这可能是由于考虑了机械通气和因果 HP-SAP 相互作用的影响；4）基于模型的闭环方法还发现，与丙泊酚麻醉期间血管扩张和心室收缩力降低相关，从 HP 到 SAP 的关系增益降低。与传统方法相比，所提出的基于模型的因果闭环方法在监测丙泊酚麻醉期间的心血管控制方面更有效，并表明 HP-SAP 闭环调节总体受到抑制。
