Magder Sheldon
Crit Care. 2012 Oct 29;16(5):236. doi: 10.1186/cc11395.
Hemodynamic monitoring is used to identify deviations from hemodynamic goals and to assess responses to therapy. To accomplish these goals one must understand how the circulation is regulated. In this review I begin with an historical review of the work of Arthur Guyton and his conceptual understanding of the circulation and then present an approach by which Guyton's concepts can be applied at the bedside. Guyton argued that cardiac output and central venous pressure are determined by the interaction of two functions: cardiac function, which is determined by cardiac performance; and a return function, which is determined by the return of blood to the heart. This means that changes in cardiac output are dependent upon changes of one of these two functions or of both. I start with an approach based on the approximation that blood pressure is determined by the product of cardiac output and systemic vascular resistance and that cardiac output is determined by cardiac function and venous return. A fall in blood pressure with no change in or a rise in cardiac output indicates that a decrease in vascular resistance is the dominant factor. If the fall in blood pressure is due to a fall in cardiac output then the role of a change in the return function and cardiac function can be separated by the patterns of changes in central venous pressure and cardiac output. Measurement of cardiac output is a central component to this approach but until recently it was not easy to obtain and was estimated from surrogates. However, there are now a number of non-invasive devices that can give measures of cardiac output and permit the use of physiological principles to more rapidly appreciate the primary pathophysiology behind hemodynamic abnormalities and to provide directed therapy.
血流动力学监测用于识别与血流动力学目标的偏差，并评估对治疗的反应。为实现这些目标，必须了解循环系统是如何调节的。在本综述中，我首先对亚瑟·盖顿的工作及其对循环系统的概念理解进行历史回顾，然后介绍一种可将盖顿的概念应用于床边的方法。盖顿认为，心输出量和中心静脉压由两种功能的相互作用决定：心脏功能，由心脏性能决定；以及回心血量功能，由血液回心量决定。这意味着心输出量的变化取决于这两种功能之一或两者的变化。我从一种基于以下近似关系的方法开始：血压由心输出量和体循环血管阻力的乘积决定，心输出量由心脏功能和静脉回心血量决定。血压下降而心输出量不变或升高表明血管阻力降低是主要因素。如果血压下降是由于心输出量下降，那么回心血量功能和心脏功能变化的作用可以通过中心静脉压和心输出量的变化模式来区分。心输出量的测量是这种方法的核心组成部分，但直到最近，心输出量都不容易获得，而是通过替代指标来估计。然而，现在有许多非侵入性设备可以测量心输出量，并允许运用生理学原理更快速地了解血流动力学异常背后的主要病理生理学情况，并提供针对性治疗。
