A nurse is teaching a client who has a new prescription for a nitroglycerin transdermal patch.
Which of the following instructions should the nurse include?

Lithium can cause hyponatremia by increasing the secretion of antidiuretic hormone and reducing the renal clearance of sodium.

Strenuous exercise can also cause hyponatremia by increasing sweat loss and fluid intake. Therefore, a client who is taking lithium and starting a new exercise program is at risk of developing hyponatremia.

Choice A is wrong because hypomagnesemia is not a common side effect of lithium or exercise.

Choice B is wrong because hypocalcemia is not a common side effect of lithium or exercise.

Choice D is wrong because hypokalemia is not a common side effect of lithium or exercise.

However, lithium can interact with some diuretics that can cause hypokalemia, so the client should avoid taking these drugs without consulting their doctor. Normal ranges for electrolytes are:

Sodium: 135-145 mmol/L

Magnesium: 0.7-1.1 mmol/L

Calcium: 2.1-2.6 mmol/L

Potassium: 3.5-5.0 mmol/L

This is because a weight gain of 2.5 kg (5 Ib) in 2 days indicates a worsening of heart failure and fluid retention, which may require an adjustment of the diuretic dose or other medications.

The provider should be informed of this change as soon as possible to prevent further complications.

Choice A is wrong because teaching the client about foods low in sodium is not the first action the nurse should take.

While a low-sodium diet is important for heart failure patients, it is not an urgent intervention and it does not address the immediate problem of fluid overload.

Choice B is wrong because determining medication adherence by the client is not the first action the nurse should take.

While it is important to assess if the client is taking furosemide as prescribed, it is not an urgent intervention and it does not rule out other causes of fluid retention, such as renal impairment or disease progression.

Choice C is wrong because encouraging the client to dangle the legs while sitting in a chair is not the first action the nurse should take.

While this may help reduce edema in the lower extremities, it does not address the underlying cause of fluid overload and it may worsen pulmonary congestion by increasing venous return to the heart.