What are the implications of cerebral salt wasting (CSW) after traumatic brain injury (TBI)?

From the Guidelines

Cerebral salt wasting (CSW) after traumatic brain injury (TBI) should be managed with aggressive sodium and fluid replacement, using 0.9% saline as the first-line fluid therapy, as recommended by the international multidisciplinary perioperative quality initiative 1. The goal of treatment is to restore volume status and correct hyponatremia, while avoiding the use of albumin due to its association with higher mortality in TBI patients 2. Key aspects of management include:

• Aggressive sodium and fluid replacement to restore volume status and correct hyponatremia
• Use of isotonic or hypertonic saline (3% NaCl) administration, with 3% NaCl typically given at 0.5-2 mL/kg/hr and titrated based on serum sodium levels
• Oral salt supplementation (3-12 g/day in divided doses) can be used in less severe cases
• Fludrocortisone (0.1-0.4 mg daily) is often added as it enhances sodium reabsorption in the kidneys
• Volume status should be carefully monitored through clinical assessment, daily weights, and fluid balance
• Serum sodium should be corrected gradually (not exceeding 8-10 mEq/L in 24 hours) to avoid osmotic demyelination syndrome
• CSW typically resolves within 3-4 weeks but can persist longer
• The condition differs from SIADH (Syndrome of Inappropriate Antidiuretic Hormone) by presenting with hypovolemia rather than euvolemia, making accurate diagnosis crucial as treatment approaches differ significantly 3. Regular monitoring of electrolytes, particularly sodium, is essential throughout treatment. It is also important to note that the primary goal for fluid therapy during neurosurgery is to maintain normal blood volume, optimize cerebral blood flow, and avoid reduction in plasma osmolarity, and that hypotonic solutions such as Hartmann’s or Ringer’s lactate are commonly avoided in favor of 0.9% saline 2.

From the Research

Definition and Diagnosis of Cerebral Salt Wasting

• Cerebral salt wasting (CSW) is a condition characterized by hyponatraemia, reduced volume status, and inappropriately high renal sodium loss, often occurring in patients with cerebral pathology 4, 5, 6.
• The diagnosis of CSW requires a high index of suspicion and distinguishing it from the syndrome of inappropriate antidiuretic hormone (SIADH) is essential for prompt treatment 4, 7.
• The hallmarks of substantial CSW include hyponatraemia, reduced volume status, and inappropriately high renal sodium loss, which can be diagnosed by measuring fractional excretion of urinary sodium and uric acid 6.

Treatment of Cerebral Salt Wasting

• Managing CSW requires correction of the intravascular volume depletion and hyponatraemia, as well as mitigation of on-going substantial sodium losses, which can be achieved with substantial volumes of hypertonic saline for a prolonged period of time 4.
• Fludrocortisone has a role in the management of CSW, as it can reduce the doses of hypertonic saline required and maintain serum sodium levels, and has been shown to be effective in several case reports 5, 6, 8.
• Treatment with fludrocortisone can be complicated by hypokalemia and hypertension, which necessitate dose reduction or brief cessation of therapy 5.

Clinical Presentation and Management Challenges

• CSW can present with hyponatraemia, polyuria, and extracellular volume contraction, and can be challenging to diagnose and manage, particularly in pediatric patients 5, 8.
• The use of fludrocortisone therapy can be an effective adjunct to treatment, but requires careful monitoring of serum electrolytes and blood pressure 5, 6, 8.
• The duration of therapy with fludrocortisone can vary from 4 to 125 days, depending on the individual patient's response to treatment 5.