An internist is preparing hospital discharge orders for a 69-year-old male who was admitte… — USMLE Step 3

An internist is preparing hospital discharge orders for a $69$ -year-old male who was admitted four days ago for an acute exacerbation of heart failure. The patient has a known history of ischemic cardiomyopathy with a left ventricular ejection fraction of $25\%$ , type 2 diabetes mellitus, and stage 3 chronic kidney disease. Following successful intravenous diuresis, he is now euvolemic and breathing comfortably on room air.

Vital signs today show a blood pressure of $118/74$ mmHg and a heart rate of $72$ /min.

Current medications planned for discharge include:
- Lisinopril $20$ mg daily
- Carvedilol $12.5$ mg twice daily
- Dapagliflozin $10$ mg daily
- Oral torsemide $20$ mg daily

Laboratory results obtained this morning:

Test	Result
Sodium	$139$ mEq/L
Potassium	$4.3$ mEq/L
Blood urea nitrogen	$24$ mg/dL
Creatinine	$1.6$ mg/dL (baseline $1.5$ mg/dL)

To fully optimize guideline-directed medical therapy, the internist plans to prescribe spironolactone before the patient leaves the hospital.

Which of the following is the most appropriate action or instruction regarding the addition of this medication?

Initiate the medication and arrange for a follow-up basic metabolic panel in one to two weeks.Answer
B
Advise the patient to replace dietary sodium with a potassium-enriched salt substitute.
C
Discontinue lisinopril to prevent the synergistic development of life-threatening hyperkalemia.
D
Defer initiation of the medication because the current serum creatinine level is an absolute contraindication.
E
Prescribe the medication and concurrently start daily naproxen to reduce the risk of diuretic-induced gout flares.

Answer

The most appropriate action is to initiate the medication and arrange for a follow-up basic metabolic panel in one to two weeks.

The correct answer involves initiating the medication and scheduling a follow-up metabolic panel in one to two weeks. Mineralocorticoid receptor antagonists (MRAs) such as spironolactone provide a significant mortality benefit in patients with heart failure with reduced ejection fraction (HFrEF). However, because they are potassium-sparing diuretics, their use carries a substantial risk of hyperkalemia and worsening renal function. This risk is heavily amplified in patients with underlying chronic kidney disease and those concurrently taking ACE inhibitors (like lisinopril), ARBs, or ARNIs. Therefore, clinical guidelines strongly recommend checking serum potassium and renal function within

1

2

weeks after initiating an MRA or increasing its dose to prevent life-threatening hyperkalemia.

Step-by-Step Solution

Identify the patient's underlying conditions and current status.

The patient has heart failure with reduced ejection fraction (HFrEF) and chronic kidney disease, and is currently euvolemic on a regimen of lisinopril, carvedilol, dapagliflozin, and torsemide.

Establishing the clinical baseline is necessary to determine what guideline-directed therapies are missing and what risks they may pose.

Evaluate the safety and indications for adding spironolactone.

Spironolactone is a mineralocorticoid receptor antagonist (MRA) indicated for HFrEF to reduce mortality. The patient's creatinine (

1.6

mg/dL) and potassium (

4.3

mEq/L) are within safe parameters for initiation.

MRAs are contraindicated in severe renal failure or baseline hyperkalemia, so lab values must be verified before prescribing.

Determine the necessary follow-up protocol for the new medication.

Guidelines mandate checking a basic metabolic panel within

1

2

weeks of starting an MRA.

The combination of an MRA, an ACE inhibitor (lisinopril), and baseline chronic kidney disease significantly elevates the risk of acute hyperkalemia and renal dysfunction, requiring prompt surveillance.

Key Concept

Initiation of mineralocorticoid receptor antagonists in heart failure requires close laboratory monitoring of potassium and renal function, typically within 1 to 2 weeks, due to the risk of hyperkalemia, especially when co-administered with ACE inhibitors.

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