Cardiovascular physiology: Integrative function

Abstract

A thorough understanding of cardiovascular physiology is a cornerstone of patient management in the perioperative period. The primary role of the cardiovascular system is to provide sufficient blood flow to satisfy the metabolic demands of the body tissues. This chapter presents the primary determinants of tissue blood flow (arterial pressure and local vascular resistance) and the factors that alter them. Because of its critical pumping role, the physiology of the heart is given particular emphasis. The major determinants of stroke volume, i.e., preload, contractility, and afterload, are discussed. Indices of cardiac function are reviewed, including cardiac output using thermodilution, ejection fraction from image-based measurements, and myocardial contractility assessed by cardiac function curves using a pulmonary artery catheter, and by end-systolic pressure-volume relations from pressure-volume loops. The determinants of coronary blood flow and myocardial oxygen demand are described, as well as how an imbalance between these variables may produce myocardial ischemia. Other topics covered include: 1) the principles of hemodynamics, and the mechanisms regulating function of the various vessel types, including the large arteries, arterioles, capillaries, and veins; 2) the transport of oxygen by blood and its delivery to the body tissues; 3) methods to measure tissue oxygen consumption, along with their advantages and limitations; 4) the role of the capillaries in tissue oxygen delivery, and in fluid filtration and absorption; 5) the responses elicited by activation of the major circulatory reflexes (the arterial baroreceptor, Bezold-Jarisch, and Bainbridge reflexes); 6) emerging developments in noninvasive perioperative cardiovascular monitoring.