A 49-year-old man who presented with chief complaint of “severe headache” was diagnosed with a subarachnoid hemorrhage (SAH) without hydrocephalus and significant neurological defects. After successful intravascular coiling of a right posterior communicating artery aneurysm, he is admitted to the intensive care unit (ICU). On postoperative day 1, patient complains of feeling weak, then becomes progressively more confused. Labs drawn prior to his seizure demonstrate the following:
Additional studies are ordered which demonstrate urine sodium of 40 mmol/L, urine osmolality of 452 mOsm/kg, and serum osmolality of 265 mOsm/kg. The patient then suffers a grand mal seizure which is terminated with intravenous levetiracetam.
Which is the most appropriate next step in management?A. Immediate reimaging and neurosurgical consult
Correct Answer: B
The patient is severely hyponatremic and symptomatic, with evidence that he has SIADH. With his underlying intracranial disease, the serum sodium must be raised quickly to prevent further cerebral edema and prevent irreversible neurologic injury. To raise the serum sodium concentration, electrolyte concentration of the fluid given must be greater than the electrolyte concentration of the urine. Thus, the administration of hypertonic saline is the only rapid way to raise the serum sodium and improve neurologic symptoms in patients with symptomatic severe hyponatremia. Fluid restriction should not be done in patients with SAH, as it may promote cerebral vasospasm.
Although there is no set protocol of hypertonic saline therapy, various studies recommend 100 mL of 3% saline given as an intravenous bolus, which should raise serum sodium approximately 1.5 mEq/L in men and 2 mEq/L in women. If neurologic symptoms persist, a 100 mL bolus of 3% saline can be repeated up to two more times at 10-minute intervals.
Of note, the serum sodium should not be raised greater than 8 to 12 mEq/L in a 24-hour period. Overly rapid correction of sodium increases risk of central pontine myelinolysis.