Albumin does not control the distribution of extracellular fluid

Dean Professor Glenister delivered the Welcome to Med School speach when I arrived at CXHMS London in 1973, and it included the famous bon mot that “half of what we will teach you is wrong, we just don’t know which half.” Well we can certainly add to the “wrong” catalogue the following: “Physiologically, maintenance of oncotic pressure/colloid osmotic pressure (COP) is considered [albumin’s] major function as it controls the distribution of extracellular fluid between the vascular and extra-vascular compartments.” This version was quoted just this year! ref. PLOS ONE | DOI:10.1371/journal.pone.0159839

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The fact that there is a higher concentration of albumin in the intravascular compartment is due to the asymmetry of the transendothelial barrier, the glycocalyx model. Admittedly this generates delta π which restricts (but never reverses) Jv, but albumin cannot be said to be a sine qua non of plasma volume. Just try telling analbuminaemic people that they should in theory not exist. “Important clinical signs are usually not present in analbuminaemia, a congenital condition inherited as an autosomal recessive trait,”

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