Peripheral Circulation

Abstract

During the two years since Peterson's review of the peripheral circulation in the Annual Review of Physiology (1), such a tremendous volume of litera ture on this subject has appeared that the references reviewed in the present paper have had to be selected with extreme care. Also, because the pharma cological aspects of the peripheral circulation were reviewed in the Annual Review of Physiology by Bovet & Carpi in 1957 (2), only those aspects of the pharmacology of the peripheral circulation that shed light on physiological mechanisms will be covered. This paper presents, first, the general dynamics of the peripheral circulation and then studies relating to certain peripheral circulatory diseases and regional vascular beds. BLOOD VOLUMEMeasurements.-The methods for measuring blood volume have been reviewed by Mertz (3). Especially interesting in the past two years has been the development of far more knowledge concerning the vascular-extravascu lar interchange of fluids and proteins (4 to 12), the lack of which has long been one of the major deterrents to accurate measurements of blood volume. Studies, particularly by Mayerson et al. (4, 5) and Huggins et al. (7 to 11), have shown that transfusion of large excesses of blood or other fluids into the circulation can sometimes so overstretch the capillaries that a "stretched pore phenomenon" (5) occurs, allowing excessive leakage not only of fluid into the extravascular spaces but also of large portions of the plasma pro tein. Becapse of this effect the usual dilution techniques for measuring blood volume become very inaccurate. However, by using radioactive protein, then allowing the plasma proteins to come to equilibrium with the extra vascular proteins, and finally mathematically accounting for the extra vascular portion of the proteins, it is possible to determine plasma volumes with reasonable accuracy even when proteins leak from the circulation very rapidly (4, 6). Regulation of blood volume.-Sjostrand (13), in reviewing the regulation of blood volume, points out that the basic regulatory factor is the capacity of the vascular system itself. The next factor of importance is the shift of fluids through the capillary membrane between the extravascular and vascu lar spaces. Following transfusion into a normal animal, fluid loss into the tissues begins immediately and continues until the blood volume is read justed to a normal value; and, conversely, following hemorrhage the dynam ics of capillary equilibrium cause an immediate onset of fluid transfer into 1 The survey of the literature pertaining to this review was concluded May 1,1958. 239 Annu. Rev. Physiol. 1959.21:239-270. Downloaded from www.annualreviews.org Access provided by University of California -San Francisco UCSF on 02/02/15. For personal use only. Quick links to online content Further ANNUAL REVIEWS

Teaching venous return without throwing students a curve

“… Here we develop a comprehensive presentation of venous return. Guyton’s venous return curve describes venous return in terms of right atrial pressure, mean circulatory filling pressure, and sympathetic activity. 1 This work demonstrated the key role of venous return in cardiac function, and it has been part of undergraduate medical education since that time. However, experience shows that venous return curves are difficult to present or understand, and have limited direct clinical application.…”