The efficacy of transfusion of blood and plasma for relief of shock has become well established. An important problem in replacement therapy is the amount of blood or plasma which is necessary for the individual patient. This depends primarily on two factors: (1) the amount of blood and/or plasma which was originally lost or which continues to be lost subsequent to the shock stimulus or as a result of additional shock stimuli, and (2) the extent to which the compensatory mechanisms of the body, such as vasoconstriction and hemodilution, can make up for the deficiency in blood volume. (Vasoconstriction attempts to adjust the size of the vascular bed to the remaining blood volume, and hemodilution endeavors to replace the loss of whole blood or plasma with tissue fluids.)
The effectiveness of the compensation for a reduction in blood volume depends to a large extent on the original condition of the