Prescribing Safety Assessment (PSA) Practice Exam

Which condition is a cause of euvolemic hyponatraemia?

1. Heart failure

2. Shock

3. SIADH

4. Acute kidney injury

The correct answer is: SIADH

Euvolemic hyponatraemia occurs when there is a low sodium concentration in the serum while the total body fluid is normal. One of the primary causes of euvolemic hyponatraemia is the Syndrome of Inappropriate Antidiuretic Hormone secretion (SIADH). In this condition, excessive release of antidiuretic hormone (ADH) leads to water retention without a corresponding increase in sodium levels. This dilution of sodium in the bloodstream results in hyponatraemia, but the body's volume remains relatively normal, hence the term "euvolemic." In contrast, heart failure and acute kidney injury typically lead to fluid overload and volume depletion respectively, altering the body’s fluid balance and leading to different forms of hyponatraemia. Shock, generally associated with significant changes in blood volume and pressure, can also lead to hypovolaemia and not euvolemia. Thus, SIADH is the distinctive condition associated with euvolemic hyponatraemia due to its mechanism of promoting water retention without isolating sodium loss.