From renal salt wasting to SIADH

Abstract

Hyponatraemia is common following major head injury and is associated with significant morbidity and mortality. A 20-year-old man presented with reduced consciousness after head trauma and was found to have a fractured skull base with bilateral frontal contusions. On day 3 of his admission, he developed hyponatraemia with raised urine sodium and osmolality, despite receiving dexamethasone and intravenous fluid therapy. His hyponatraemia worsened after the treatment with fluid restriction and oral salt. He was in negative fluid balance suggesting possible renal salt wasting. A trial of isotonic normal saline resulted in a further fall in serum sodium level. He was subsequently treated for suspected syndrome of inappropriate ADH with a hypertonic (3%) saline infusion. His sodium level and neurological status improved. This case report illustrates the confounding factors that commonly affect clinical decision-making when treating patients with hyponatraemia following head injury. The guidelines for diagnosis and management are discussed.

Keywords: fluid electrolyte and acid-base disturbances; medical management; neurological injury.

Figure 1

(Left) CT demonstrates a fracture extending from the right lambdoid suture into the mastoid process is shown. A further longitudinal fracture of the mastoid process and a subtle fracture in the posterior wall of the right sphenoidal sinus were also seen but not demonstrated in this slice. (Right) There are petechial haemorrhages in the inferior aspect of both frontal lobes consistent with brain contusions.

Figure 2

Changes in serum sodium.

Figure 3

Changes in fluid intake, output and balance.