A senior nurse is providing instructions to a newly hired nurse about caring for clients who are receiving diuretic therapy to treat heart failure. The senior nurse should explain that which of the following medications puts clients at risk for both hyperkalemia and hyponatremia?

A) Spironolactone:
Spironolactone is a potassium-sparing diuretic commonly used in the treatment of heart failure. Unlike other diuretics, spironolactone works by antagonizing aldosterone, a hormone that promotes sodium and water retention and potassium excretion. By blocking aldosterone's action, spironolactone prevents the kidneys from excreting potassium, thus increasing potassium levels in the blood (hyperkalemia). Additionally, spironolactone can lead to hyponatremia (low sodium levels), as it also causes the kidneys to retain sodium and water, diluting sodium levels in the blood.

B) Furosemide:
Furosemide, a loop diuretic, is typically used in heart failure to remove excess fluid. It works by inhibiting the reabsorption of sodium, chloride, and potassium in the loop of Henle, which increases urine output. While furosemide can cause hypokalemia (low potassium levels) due to the increased excretion of potassium, it does not typically cause hyperkalemia.

C) Hydrochlorothiazide:
Hydrochlorothiazide is a thiazide diuretic, which works by inhibiting sodium and chloride reabsorption in the distal convoluted tubule of the kidney, leading to increased urine production. Thiazide diuretics can cause hypokalemia (low potassium levels) and hyponatremia (low sodium levels) due to the enhanced excretion of both electrolytes.

D) Metolazone:
Metolazone is also a thiazide-like diuretic that works similarly to hydrochlorothiazide. It can cause hypokalemia and hyponatremia, but like hydrochlorothiazide, it does not typically cause hyperkalemia. Metolazone is more potent than hydrochlorothiazide but still does not carry the risk of hyperkalemia like spironolactone does.

A) Prepare the client for mechanical ventilation:
A myasthenic crisis is a medical emergency characterized by severe weakness of the respiratory muscles, leading to respiratory failure. This can result from insufficient levels of acetylcholine due to insufficient medication (e.g., pyridostigmine) or from an infection. In such cases, airway support is the priority. The nurse should first prepare the client for potential mechanical ventilation to ensure they can breathe properly and to prevent respiratory arrest.

B) Instruct the client to perform pursed-lip breathing:
While pursed-lip breathing is a useful technique to help with shortness of breath and improve ventilation in certain respiratory conditions (like COPD), it is not the first action in managing a myasthenic crisis. The immediate priority is to ensure the client can breathe and maintain oxygenation, which may require mechanical ventilation if the respiratory muscles are too weak to support breathing effectively.

C) Prepare to administer IVIG:
IV immunoglobulin (IVIG) can be used in the treatment of myasthenic crisis by suppressing the immune response and increasing acetylcholine receptor activity. However, IVIG is not typically the first intervention. Respiratory support and stabilization should take precedence, especially if there is significant respiratory distress.

D) Administration of an immunosuppressant:
Immunosuppressive therapy, such as corticosteroids or azathioprine, may be used to manage myasthenia gravis over the long term, but it is not an acute intervention for a myasthenic crisis. The immediate priority in a crisis situation is to manage respiratory distress and ensure airway protection.