Peritoneal dialysis solutions containing glucose polymers are becoming more popular, particularly in patients on APD who tend to retain fluid during their daytime fills. The rationale for their use is that they lead to a reduced absorption of the solute with more ultrafiltration. The commonest fluid used currently is icodextrin which comes in a 7.5% solution and is generally regarded as being safe and well tolerated albeit with a slightly increased incidence of cutaneous reactions compared with traditional, dextrose-containing solutions. However, there is one side effect which is potentially life-threatening if unrecognized.
A 60-year-old patient on PD with a history of poorly controlled diabetes presented to the ED with nausea, slurred speech and drowsiness. Fingerstick blood sugar was elevated at 360mg/dl. He was started on an insulin infusion and had a CT brain that had no acute changes. Despite the insulin infusion, his blood glucose remained elevated and a simultaneous blood sugar was sent to the lab which came back at 24. He was immediately given a glucose bolus and his symptoms resolved.
Icodextrin is not metabolized in the peritoneum. However, it can cross into the systemic circulation at which point it is metabolized to maltose. Some commercial blood sugar test strips cannot distinguish between glucose and other sugars which, under normal circumstances, are not present in large amounts in the blood. Specifically, strips that contain a reagent called glucose dehydrogenase with coenzyme pyrroloquinolinequinone (GDH PQQ) will give falsely elevated blood sugar readings in patients who use icodextrin. Reagent strips that use glucose oxidase and glucose hexokinase (GDH-NAD, GDH-FAD) do not detect other sugars and thus are more accurate in patients receiving icodextrin. There have been a number of severe adverse events reported to the FDA related to this side-effect and at least one death.
Interestingly, this is not limited to PD patients. A similar problem has been noted with some immunoglobulin preparations which also contain maltose. Other sugars which may cause falsely elevated blood glucose readings include galactose and xylose. Thankfully, my institution uses GDH-NAD so this has not been an issue but it is something to be aware of in PD patients with elevated blood sugars and inconsistent symptoms. See this case report from the BMJ for details.