cerebral salt wasting (CSW)

Last reviewed 01/2018

Cerebral salt wasting (CSW)

• a syndrome that occurs after head injury or neurosurgical procedures
• initiating event is loss of sodium and chloride in the urine, which results in a decrease in intravascular volume leading to water retention and hyponatraemia because of a baroreceptor-mediated stimulus to arginine vasopressin (AVP) secretion.
• CSW resembles SIADH: both are hyponatremic disorders seen after head injury with relatively high urine sodium excretion rates and urine osmolality, along with plasma arginine vasopressin (AVP) levels that are inappropriately high in relation to serum osmolality
  • in patients with CSW the increase in AVP is secondary to volume depletion
    • this contrasts with SIADH where a high AVP level is the primary aetiologic event - who are euvolaemic or have a modest increase in plasma volume from water retention
    • high urine sodium is not the cause of the hyponatraemia in SIADH - it consequence of the modest volume expansion and need to maintain sodium balance in the face of continuing sodium intake
  • relative distribution of CSW and SIADH among neurosurgery patients with hyponatraemia is unknown
  • aetiology of CSW has not been definitively established
  • differentiation of CSW from SIADH - requires establishment that a period of urinary sodium loss and volume depletion preceded development of hyponatraemia

Reference:

• (1) hyponatraemia Treatment Guidelines 2007: Expert Panel Recommendations.American Journal of Medicine 2007; 120 (11);S1:S1-S21.