Misdiagnosing CSW as SIADH can lead to dangerous fluid restriction, increasing the risk of vasospasm and cerebral infarction.
Metabolic Sentinel Probe
Input the clinical volume status and urinary biochemical markers to establish the differential profile between SIADH and Cerebral Salt Wasting (CSW).
Guidelines & Evidence
Clinical Details
Section 1
When to Use
When to Use
Evaluating hyponatremia in a patient following subarachnoid hemorrhage (SAH), head trauma, or neurosurgery.
Deciding between fluid restriction vs aggressive fluid resuscitation in neurological hyponatremia.
Section 2
Literature
Pathophysiology
SIADH is the inappropriate release of ADH, causing the kidneys to retain free water, which dilutes serum sodium (euvolemic hyponatremia). Cerebral Salt Wasting (CSW) is defined by the brain releasing natriuretic peptides (BNP/ANP) in response to injury, forcing the kidneys to aggressively dump sodium into the urine. Water follows the sodium out, leading to severe volume depletion alongside hyponatremia (hypovolemic hyponatremia).
Section 3
Pearls/Pitfalls
The Fatal Mistake: Fluid Restricting CSW
The biggest danger is misdiagnosing CSW as SIADH due to identical lab profiles (low serum Na, high urine Na). If you fluid restrict a patient with CSW (particularly an SAH patient), they will become profoundly hypovolemic, which precipitates severe cerebral vasospasm and catastrophic ischemic strokes. The paramount clinical distinction is VOLUME STATUS (CSW is dry; SIADH is wet/euvolemic).
Section 4
Evidence Appraisal
Primary Reference
Cerebral salt wasting syndrome: review
Cerdá-Esteve M et al. • Eur J Intern Med. 2008;19(4):249-54
