Tonicity Matters, Especially in Complex Hyponatremia Resulting from Pseudo-, Trans-locational, and True Hypotonic Hyponatremia: An Educational Case Report

Abstract

Serum tonicity is defined by the serum concentrations of sodium (sNa) and glucose, which can promote free water movement across intra/extracellular compartments. Rapid changes in serum tonicity can cause brain damage. We herein report an educational case of a patient with hyponatremia (sNa: 112 mEq/L) concomitant with acute alcoholic pancreatitis. The cause of hyponatremia was considered complex. Pseudo-and trans-locational natremia was secondary to hyperglycemia (721 mg/dL) and hypertriglyceridemia (1768 mg/ dL), respectively, and true hypotonic hyponatremia. Regarding sNa correction, rapid correction was suspected. However, this was safely managed by monitoring tonicity (not sNa or osmolarity), thereby avoiding brain damage.

Tonicity or serum osmolality? Comment on management of hyperosmolar hyperglycaemic state in adults: An updated guideline from the Joint British Diabetes Societies for Inpatient Care Group

“…We previously reported a complex case of hyponatraemia with an inverse trajectory of serum osmolality and tonicity. 2 In cases involving sodium abnormalities, correction of sNa should be done carefully because rapid changes in sNa can potentially cause brain damage. While hypernatremia can lead to cerebral oedema, hyponatraemia can result in osmotic demyelination syndrome (ODS).…”