Monday, January 21, 2019

Topic Discussion: Icodextrin and it's important pseudo-lab effects

Icodextrin is a glucose polymer used in peritoneal dialysis to help in improved clearance and ultrafiltration. Laboratory and metabolic effects of icodextin is important to know( especially the effect on glucose, Na and serum osmolarity)

There are a few that are important to remember

1.      The predominant circulating metabolites of icodextrin are maltose , maltotriose , and maltotetraose, with little glucose released in the systemic circulation due to the absence of circulating maltase. The release of glucose from the metabolized polymers occurs predominantly during the intra-cellular metabolism of maltose or other polymers by way of cellular enzymes involved in carbohydrate metabolism.

2.       The “glucose load” arising from the use of icodextrin is “functionally invisible” to the peritoneal cavity and systemic circulation, and its predominant systemic exposure is intracellular.

3.      In contrast to the acute hyperglycemia and hyperinsulinemia associated with glucose-based solutions, icodextrin does not lead to hyperglycemia or hyperinsulinemia following its intraperitoneal administration. 

4.      Point of care glucose testing might not be accurate when using icodextrin and serum glucose values should be used for insulin management.  Maltose interferes with glucose assays that utilize glucose dehydrogenase enzymes of the pyrroloquinolinequinone class (GDH PQQ), causing falsely elevated readings. The overestimation of glycemia is likely due to the presence of maltose and other oligosaccharide metabolites of icodextrin in the systemic circulation and the reaction of GDH-PQQ with the free reducing group of the glucose molecule located at the end of each saccharide chain.

5.      The decline in serum sodium and chloride associated with icodextrin therapy is caused mainly by a dilutional effect resulting from blood levels of icodextrin metabolites, particularly maltose and maltotriose. The presence of osmotically active particles in the vascular compartment is sufficient to cause a slight shift in water from the interstitial and cellular compartments to the vascular compartment, resulting in the dilutional hyponatremia (sometimes called hypertonic hyponatremia). It is like having hyperglycemia or mannitol induced hyponatremia.  

6.      Use of icodextrin has been associated with a slight increase in plasma osmolality in some studies. It can last up to 2 weeks after discontinuing icodextrin

7.      A small increase in mean serum alkaline phosphatase  has been reported in some studies of icodextrin Increases in alkaline phosphatase are not associated with true liver or billiary disease.

8.      Icodextrin interferes with amylase activity measurements by acting as a competitive inhibitor in the amylase activity assay.

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