An important message regarding the current COVID-19 pandemic. Click here to read more.

Exercise Induced Hyponatremia


Step 1: View clinicals

A 35 year old marathon runner is brought in after falling down and developing a generalised tonic-clonic seizure lasting 3 minutes. He had been running for 5 hours continuously at that time, in a very hot climate. His medical history is unremarkable, and there is no family history of cardiac disease or early deaths. His random plasma glucose is 83.8 mg/dl.

Step 2: Order all relevant investigations

Arterial Blood Gases

On room air: PO2: 80 mmHg (> 75) PCO2: 37 mmHg (35 - 45) pH: 7.4 (7.35 - 7.45) HCO3: 24 mmol/l (22 - 26)


The EEG shows only generalized slowing compatible with a postictal state.

CT Brain

The CT scan demonstrates effacement of the cortical sulci and basilar cisterns. There is no midline shift, or evidence of hemorrhages or mass lesions.

Serum Electrolytes

Na+ 116 mmol/l (135 - 145) K+ 4.7 mmol/l (3.5 - 5.5) Cl- 97 mmol/l (95 - 105)

Step 3: Select appropriate management

Hypertonic saline
Fluid restriction
DVT prophylaxis
IV 50% glucose stat

Score: ★★☆