Too Sweet to Be True: Erythritol-Induced Hyponatremia

Introduction: Natural and artificial sweeteners are commonly used glucose substitutes. They are usually well tolerated; hyponatremia secondary to oral sugar alcohols is not an established side effect. We present a case of hyponatremia due to erythritol-based sweetener use. Case Description: A 86 year old diabetic lady presented to the ED with right-side weakness confirmed on physical exam. She was hypertensive (BP187/90 mmHg), otherwise stable. Brain scan revealed left occipital lobe ischemic punctate lesions. Given the late presentation, she was not a candidate for invasive therapy. Labs revealed hyponatremia with sNa132 mmol/L. 24 hrs after admission, sNa dropped to 123 mmol/l (126 mmol/L corrected for glucose). Measured serum osmolarity 287 mOsm/kg with osmolar gap of 21 mOsm/kg. Urine Na < 20 mmol/L and urine osmolarity 305mOsm/kg. The repeat serum osmolarity was 297 mOsm/Kg. The iso-osmolar hyponatremia at that time was attributed to hyperglycemia and iodine contrast. Hyperglycemia management ensued; the patient was given intermittent normal saline boluses to ensure normovolemia. The sNa rose to 130 mmo/l before dropping again to 127 mmol/L a day later. A free water restriction followed, but her sodium remained between 127 and 130 mmol/l. Repeat workup revealed normal serum glucose, measured serum osmolarity of 323 mOsm/kg and osmolar gap of 44 mOsm/kg, urine Na 26 mmo/l and urine osmolarity of 314 mOsm/kg. Renal function, anion gap, total protein, and lipid panel were normal. SPEP were negative, and she had normal AM cortisol. During hospitalization, her urine output ranged from 600 -1400ml/24hrs. Finally, it was noted that she was using PYURE® sweetener numerous times a day as a glucose substitute. We asked her to stop the pyure®, and sodium improved in the subsequent days, and she was discharged with a normal sNa. Discussion: In our case, we argue that the hyponatremia is related to increased serum osmolarity, with the sugar alcohol use causing osmotic shift of intracellular free water and hence an iso-osmolar/hyperosmolar hyponatremia. The fluctuation in serum osmolarity and osmolar gap possibly reflects the relationship of blood sampling to time of consumption and excretion of erythritol. Finally, stopping the offending agents corrected the hyponatremia, and considering it in the rare differentials of iso/hyperosomolar hyponatremia may save resources and time for patients and healthcare.