Two weeks after initiating antihypertensive therapy, a 65-year-old man presents to the amb… — USMLE Step 3

Two weeks after initiating antihypertensive therapy, a 65-year-old man presents to the ambulatory care clinic for reassessment. His medical history is significant for type 2 diabetes mellitus complicated by microalbuminuria. At his previous visit, his blood pressure was $158/94$ mm Hg, and lisinopril was prescribed. Currently, the patient is asymptomatic, specifically denying dizziness, headaches, or peripheral swelling. Vital signs today show a blood pressure of $132/82$ mm Hg and a pulse of $72$ /min. Physical examination is unremarkable.

A basic metabolic panel is obtained today, and the results are compared to his baseline labs from two weeks ago:

Parameter	Baseline (2 weeks ago)	Current (Today)
Serum sodium	140 mEq/L	139 mEq/L
Serum potassium	4.3 mEq/L	4.8 mEq/L
Blood urea nitrogen	18 mg/dL	22 mg/dL
Serum creatinine	1.5 mg/dL	1.8 mg/dL

Based on these findings, which of the following is the most appropriate next step in the management of this patient?

A
Discontinue lisinopril and initiate amlodipine
B
Order a renal Doppler ultrasound
Continue lisinopril and schedule a routine follow-upAnswer
D
Admit the patient to the hospital for intravenous fluid resuscitation
E
Add aliskiren to the current medication regimen

Answer

Continue lisinopril and schedule a routine follow-up

The patient's serum creatinine increased from

1.5

mg/dL to

1.8

mg/dL after starting lisinopril, representing a

20

% rise from baseline. Angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs) decrease intraglomerular pressure by causing preferential vasodilation of the efferent arteriole. This hemodynamic change is beneficial for long-term renoprotection, particularly in patients with diabetic nephropathy, but it predictably reduces the glomerular filtration rate (GFR) slightly and increases serum creatinine. Current guidelines assert that a rise in serum creatinine of up to

30

% from baseline within the first few weeks of initiating an ACE inhibitor is acceptable. Because this patient's increase (

20

%) is within the acceptable limit and his potassium level remains within normal limits (

4.8

mEq/L), the most appropriate action is to continue the medication and proceed with routine outpatient monitoring.

Step-by-Step Solution

Calculate the percentage increase in serum creatinine from baseline.

1.8 - 1.5 = 0.3

mg/dL increase, which represents a

20

% rise.

To determine if the decline in renal function falls within the expected, safe physiological limits.

Evaluate the serum potassium level.

Potassium increased from

4.3

4.8

mEq/L, remaining within the normal range.

ACE inhibitors block aldosterone production, which can cause hyperkalemia. Levels must be monitored to ensure safety.

Determine the clinical significance of the laboratory changes.

The

20

% creatinine increase is below the

30

% threshold for concern, and the patient is asymptomatic with improved blood pressure.

An increase in creatinine of up to

30

% is expected due to efferent arteriolar vasodilation and is associated with long-term renoprotection.

Key Concept

An isolated increase in serum creatinine of up to 30% from baseline is an expected, benign physiological response to ACE inhibitor initiation and does not require medication discontinuation if hyperkalemia is absent.

Question

Answer

Step-by-Step Solution

Key Concept

Common Mistakes

Topics

More questions from this topic