Dextran biodegradability

Although smaller molecules of dextran (below ca. 35 kDa) can normally be eliminated renally (provided urine production is adequate), one important advantage of dextrans relative to other colloids such as HES is that dextran can also be fully degraded by dextranase in the liver or reticuloendothelial system. In this case, dextran is degraded to water (H2O) plus carbon dioxide (CO2), which means that complete elimination can be achieved via the lungs, even in patients with renal insufficiency.  

Most of the original research on dextran metabolism using C14 isotope labelling was done 50-60 years ago1,2 when dextrans were first launched as plasma substitutes. An updated study was performed in 19923 where isotope (C14) labelled dextran was given to both normovolemic and haemorrhaged hypovolemic rabbits. After 96 hours, the concentration of C14-labelled dextran was about 20-fold higher in the liver than in other organs tested (lung, kidney, spleen). Dextranase activity was also significantly higher in the liver than in other organs.

In the first 2-4 hours most dextran is excreted renally into the urine, while smaller molecules below the renal threshold (Mw 35 -55 kDa) pass through the kidneys and leave larger molecules in circulation. These remaining larger molecules are metabolised in the liver and the reticuloendothelial system to water and carbon dioxide.