CHAPTER 4 



Blood volume 



TORGNY SJO STRAND | Laboratory of Clinical Physiology, Karolinska sjukhuset, Stockholm, Sweden 



CHAPTER CONTENTS 



Noiinal Values in Animals and in Man 



Evaluation of Results Obtained by Different Methods 



Variation in Blood Volume with Body Size 



Variation with Body Type 



Variation with Sex 



Variation with Age 

 Internal Factors that Affect Blood Volume 



Plasma Volume/Cell Volume Ratio 



Arterial Oxygen Content 



Basal Metabolic Rate 



Hormone Levels 



Intravascular Pressure 



Increased Cardiac Output 



Pregnancy 

 External Factors that Affect Blood Volume 



Season 



Climate 



Barometric Pressure 

 Circumstantial Factors that Affect Blood Volume 



Nutrition 



Physical Activity 



Stress 

 Experimental Situations that Affect Blood Volume 



Body Position 



Physical Work 



Bleeding 



Blood Transfusion 



Plasma Expander Infusions 

 Regulation of Blood Volume 



Regulation of the Body's Water Balance 



Factors Influencing Distribution of Water Between Blood 

 Vessels and Extracellular Space 



Factors Influencing the Capacity of the Vascular System 



Regulatory Mechanisms 



Regulation of Hematopoietic Acti\ity 



THE BLOOD may be regarded as a tissue consisting of 

 cells and intercellular substance which fills the vas- 

 cular system. Thus, the blood volume varies with the 

 vascular system and its adjustment to the size and 

 metabolism of the tissues which it supplies. 



The blood volume may also be regarded as the 



volume of fluid in a closed pumping system with 

 elastic "pipes," in which the maximal rate of flow is 

 determined (among other things) by the fluid volume 

 and the filling pressure of the pump. It is therefore to 

 be expected that the total blood volume is adjusted 

 to meet the maximum circulatory requirements that 

 arise under different conditions. These requirements 

 vary with external circumstances, which primarily 

 influence the development and functional capacity of 

 the locomotive organs. 



The variations of blood volume between individuals 

 and in an individual should be analyzed from these 

 two viewpoints in order to determine whether such 

 variations are bound by any laws. This also applies 

 to the regulation of the total volume of blood and its 

 composition of cellular elements and plasma. Accord- 

 ingly, the blood \olume, regarded as a tissue, can be 

 expected to have a certain optimum in relation to the 

 supplied tissues, as well as a certain optimal ratio 

 between cells and plasma. In the hemodynamic 

 adjustment, other additional factors can be expected 

 to influence these relationships. 



NORMAL VALUES IN ANIMALS AND IN MAN 



Evaluation of Results Obtained by Different Methods 



Up to the present numerous values for blood 

 volumes, plasma volumes, and red cell volumes in 

 diff'erent animals have been published. In many cases, 

 however, the determinations are not directly com- 

 parable, because different methods have been used. 

 Earlier direct determinations of blood volume with 

 bleeding-out and infusion of the vessels are, on the 

 whole, mutually comparable but not directly by 

 indirect dilution methods. Values obtained by indirect 

 methods based on determination of the plasma volume 

 differ significantly from values obtained by the 

 methods by which the blood cell volume is directlv 



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