Correct Answer: A

Rationale: To calculate the volume to administer, use the formula: (Desired dose / Concentration) = Volume to administer. In this case, (15,000 units / 20,000 units/mL) = 0.75 mL, which is rounded up to 0.8 mL. Therefore, the healthcare professional should administer 0.8 mL per dose of heparin.

Correct Answer: D

Rationale: An adverse effect of prochlorperazine is acute dystonia, which is evidenced by spasms of the muscles in the face, neck, and tongue. Diphenhydramine is used to suppress extrapyramidal effects of prochlorperazine, making it the most appropriate choice to address the client's spasms.

Correct Answer: C

Rationale: In older adults, reduced hepatic function can lead to prolonged effects of medications metabolized by the liver. This prolonged effect may result in drowsiness the next morning. Adjusting the dosage of the hypnotic medication may be necessary for this client.

Correct Answer: C

Rationale: A serum potassium level of 5.2 mEq/L indicates hyperkalemia. Spironolactone is a potassium-sparing diuretic that can cause potassium retention. Hyperkalemia is a serious condition that can lead to cardiac dysrhythmias. The healthcare professional should withhold the medication and promptly notify the provider to prevent potential complications.

Correct Answer: A

Rationale: Orthostatic hypotension is a known adverse effect of MAOIs, such as Phenelzine. It is characterized by a drop in blood pressure upon standing, which can lead to dizziness or fainting. Monitoring for orthostatic hypotension is crucial when administering MAOIs to prevent potential complications.