The primary care provider prescribes intravenous fluid replacement therapy with potassium chloride to be added for a child with severe gastroenteritis. Before adding the potassium chloride to the...

The primary care provider prescribes intravenous fluid replacement therapy with potassium chloride to be added for a child with severe gastroenteritis. Before adding the potassium chloride to the intravenous fluid, which of the following assessments would be most important?

1. Ability to void.

2. Passage of stool today.

3. Baseline electrocardiogram.

4. Serum calcium level.