This chapter has some borderline relevance to Section I1(i) of the 2017 CICM Primary Syllabus, which expects the exam candidate to "explain the ...movement of body fluids". Any mention of fluid movement must sound dangerously circulatory in character, and it is true that the bulk of these discussions takes place wherever the circulatory system is discussed. Still, the college wants what it wants, and so this chapter is left here as a brief summary of the forces that govern transvascular fluid movement. Let's call them Starling forces.
Starling, in 1896, published a paper on the absorption of fluids from the connective tissue spaces. The basis of his work were a series of experiments injecting serum or saline solution into the hindlimb of a dog, to track the movement of extravascular fluid. From his findings, Starling deduced that the capillaries and post-capillary venules behave as semi-permeable membranes absorbing fluid from the interstitial space. Thereafter, the true "classical model" of Starling's Principle finally took its modern form in the hands of Krogh, Landis and Turner (1931):
This is consistent with the current data:
(It is now thought that the intravascular volume increase which occurs with the administration of hyperoncotic albumin is likely the result of water moving into the circulation out of the non-circulating glycocalyx, which contributes about 25% to the total intravascular volume).