Review Question - QID 105019

This patient is presenting with a severe headache, a head CT demonstrating blood in the subarachnoid space, and cerebral T waves on ECG suggesting a diagnosis of a subarachnoid hemorrhage (SAH). Hyponatremia commonly occurs in patients who experience a SAH.

SAH typically presents with a sudden/severe thunderclap headache and can be diagnosed with a head CT demonstrating blood in the subarachnoid space or with a lumbar puncture demonstrating xanthrochromia and red blood cells in the CSF. Hyponatremia after SAH is relatively common (occurring in an estimated 10-40% of cases). This abnormality typically manifests within 10 days of initial presentation. The 2 primary/suspected causes of hyponatremia in SAH include syndrome of inappropriate antidiuretic hormone secretion (SIADH) versus cerebral salt wasting.

Figure/Illustration A is a CT of the head showing blood in the subarachnoid space (red circle). Figure/Illustration B is an ECG demonstrating cerebral T waves (red arrows).

Incorrect Answers:
Answer 1: Hyperkalemia presents with peaked T waves and QRS widening on ECG and is likely to develop in a patient with kidney failure.

Answer 2: Hypermagnesemia presents with somnolence and decreased reflexes and is common in kidney failure and patients being treated for preeclampsia/eclampsia.

Answer 3: Hypernatremia is common in dehydration and can be treated with IV fluids slowly. Rapid treatment of hypernatremia can cause seizures secondary to cerebral edema.

Answer 5: Hypokalemia presents with muscle weakness and U waves on ECG and can occur in insulin overdose, when continuous albuterol nebulizers are given, or in metabolic alkalosis.

Bullet Summary:
Hyponatremia secondary to SIADH and cerebral salt wasting is a common electrolyte complication in subarachnoid hemorrhage.