Is "cerebral hyponatraemia" iatrogenic?

Area of Science:

• Neurology
• Endocrinology
• Nephrology

Background:

• Hyponatraemia and hypoosmolality are commonly observed in patients with central nervous system (CNS) disease or trauma.
• These electrolyte imbalances are frequently attributed to the inappropriate secretion of antidiuretic hormone (ADH), a condition termed the syndrome of inappropriate antidiuretic hormone secretion (SIADH).
• A "cerebral" aetiology for these changes has been previously postulated.

Purpose of the Study:

• To re-evaluate the aetiology of hyponatraemia in patients with CNS disease or trauma.
• To determine if the observed increase in antidiuretic activity is truly inappropriate or a physiological response.
• To provide recommendations for fluid management in this patient population.

Main Methods:

• Review of published reports on hyponatraemia in CNS disease.
• Analysis of data from the present study concerning antidiuretic activity and fluid balance.
• Correlation of clinical findings with laboratory parameters.

Main Results:

• The increase in antidiuretic activity observed in patients with CNS disease or trauma is generally appropriate and expected.
• Hyponatraemia in these patients is suggested to be primarily caused by excessive administration of intravenous fluids.
• The data challenges the prevailing notion of widespread inappropriate ADH secretion as the sole cause.

Conclusions:

• The hyponatraemia observed in CNS disease or trauma is likely a result of iatrogenic fluid overload rather than inappropriate ADH secretion.
• Intravenous fluid administration in patients with CNS disease or brain injury should be strictly limited during acute stress.
• A fluid intake of approximately 1 litre per day (e.g., 2.5% glucose in 0.45% saline for a 70 kg adult) is suggested.