Icodextrin (ICO) Lowers Serum Sodium (Na) in Dose-Dependent Fashion

Introduction: ICO is widely used in peritoneal dialysis (PD). Hyperosmolar hyponatremia (hypoNa) has been reported as an adverse event of ICO but it is unknown whether there is a dose effect relationship between the two. We present a case demonstrating this relationship. Case Description: A 34.5 Kg woman with ESKD began PD with a single daily dwell of 1L of ICO. Her serum Na (mmol/L) fell from 138.9 ± 2.2 (SD) to 133.6 ± 2.1. She developed a pericardial effusion prompting a change in prescription (Rx) to 4 exchanges of 1.5L, 1.5% dextrose; Na rose to 138. Her effusion improved, and Rx was switched back to 2 cycles of 1.5L of ICO. 11 days later Na was 122. Measured serum osmolality (osm) was 302 with calculated osm 264 and a gap of 38. Whole blood Na matched serum Na. She was intravascularly contracted and given boluses of NS and the same PD Rx was continued. She had a mild increase in Na (≤ 129) but never achieved normonatremia. One month later she was still hypoNa at 121. The Rx was decreased to 1 cycle of 1.5L ICO and Na improved to 125. Her Rx was switched to 3 cycles of 1.5% dextrose with no ICO, and Na improved to 135, during which measured serum osm was 299 and calculated osm of 291 with a gap of 8. She maintained normonatremia (139.2 ± 1.5) for the subsequent 2 years – all while her Rx was dextrose based. Years later a single 2L ICO dwell was started, and she developed hypoNa (131). ICO was stopped, and Na normalized. Discussion: HypoNa is a risk factor for ESKD patients that leads to increased morbidity and mortality. ICO can cause increases in serum osm and hypoNa, the degree of which, we've shown, is related to the dose of ICO used. The concentration of ICO [ICO] is 75g/L (7.5%). We plotted the Na vs [ICO] and show a strong correlation (R2 >0.7). For patients considering stopping ICO due to hypoNa it may be reasonable to lower the dose instead.Serum Na vs. total daily ICO in grams