To the Editor:—
I wish to report a little-known and potentially dangerous mechanism of interference between Extraneal® (Baxter Healthcare Corporation, Deerfield, IL) peritoneal dialysis solution and the Accu-Chek® (Roche Diagnostics, Basel, Switzerland) blood glucose test strip monitor. Extraneal® is being integrated into continuous ambulatory peritoneal dialysis regimens because of its increased ultrafiltration and its extralong dwell (time a solution resides in the abdomen). Unfortunately, this new solution interferes with most modern capillary glucose strip–based measuring devices, including the Accu-Chek® brand. The test strip devices can dangerously overestimate the true blood glucose, potentially leading to erroneous treatment and hypoglycemia. A full year before the Food and Drug Administration approved Extraneal® in the United States in December 2002, a case series in a British diabetes journal highlighted this concern.1Several patients in that report experienced symptomatic hypoglycemia although their glucose strip machine reported a normal or even increased blood sugar. This year, a case report published in Diabetes Care , the journal of the American Diabetes Association, described a patient on Extraneal® who fell into a hypoglycemic coma secondary to this interference in capillary blood glucose measurement.2As anesthesiologists, we must be aware of this potentially lethal monitoring malfunction, especially because during anesthesia, there may be no other clinical warnings of hypoglycemia.
The mechanism behind this interference is quite interesting.3Icodextrin, a starch-derived, water-soluble glucose polymer, is the osmotically active colloid in the Extraneal® formulation. Up to 40% of indwelling icodextrin is systemically absorbed and then metabolized by α-amylase into several oligosaccharides, including maltose, maltotriose, and maltotetrose. Although the serum metabolite concentration peaks at the end of the long dwell (approximately 12 h after infusion into the peritoneum), metabolites remain in the circulation for a full 7 days after the last dwell. Many handheld blood glucose monitors use a glucose dehydrogenase–based method to determine glucose concentration, and both maltose and maltriose interfere with this test, leading to a falsely increased reported value. In contrast, laboratory-based blood glucose–quantifying machines typically use the glucose oxidase–based method, which does not interfere with icodextrin metabolites, thus providing an accurate measurement. In conclusion, before relying on handheld glucose monitors, we must be sure that the specific monitor is compatible with icodextrin-based peritoneal dialysis.
UCLA Medical Center, Los Angeles, California. firstname.lastname@example.org