Jan Wernerman’s respected team at the Karolinska are publishing interesting data from their investigations into perioperative and inflammatory hypoalbuminaemia. Followers of fluidphysiology.org understand that albumin has two vital circulations; in steady state conditions most of our albumin is within the extravascular circulation of interstitial fluid. Acute dehydration can increase the plasma concentration of albumin, and haemorrhage entails true albumin loss, but in many illnesses it is a rebalancing of the distribution of albumin that contributes to the hypoalbuminaemia that is documented and is a crude indicator of the severity of illness.
In PMID:26313170 Wernerman’s team report that plasma albumin concentration was reduced by a third two days after major surgery. Did they find an associated reduction in plasma volume? No, as I try hard to explain, albumin is not necessary for the maintenance of plasma volume. Ask any congenitally analbuminaemic person. Inflammatory markers two days after surgery were at their highest, so did they document an increased capillary escape rate of albumin? No, TCER Alb was normal. Raised TCER Alb would mostly be due to convective paracellular escape and so we may deduce that capillaries in these patients were not ‘leaky’, whether by ‘leaky’ you mean volume flow of solvent or mass transit of albumin. So was albumin synthesis raised to correct the hypoalbuminaemia or reduced as a contributory cause of the hypoalbuminaemia? Neither; albumin synthesis rate was normal.
In PMID:27846908 further data are added. Hypoalbuminaemic patients with inflammatory intra-abdominal disease were also found to have normal TCER Alb and albumin synthesis.TCER Alb is elevated at the end of a major surgical procedure, and then a new steady state with apparently low plasma albumin is established.
I have recently highlighted the important discovery that in the presence of acute phase proteins laboratory measurement of albumin becomes inaccurate and exaggerates the true magnitude of hypoalbuminaemia. (doi:10.1371/journal.pone.0159839.g001) This, plus a small salt and water retention under adrenal control, could account for the Karolinska data.