In a patient on lisinopril who is dehydrated and now has elevated blood urea nitrogen, serum creatinine, and serum potassium, is this acute kidney injury from the ACE inhibitor and volume depletion, and what immediate management steps should be taken?

ACE Inhibitor-Induced Acute Kidney Injury with Volume Depletion

Yes, this is acute kidney injury (AKI) from the combination of lisinopril and volume depletion, and you must immediately discontinue the lisinopril, stop any diuretics, and restore intravascular volume. 1, 2

Diagnosis Confirmation

This patient meets KDIGO criteria for AKI Stage 1 based on the creatinine rise from 1.2 to what appears to be a higher value (exact current value not stated, but BUN elevated and potassium now concerning). 1 The clinical picture is classic for prerenal azotemia from ACE inhibitor use in a volume-depleted state:

• Initial labs showed borderline hyperkalemia (5.0 mmol/L) with mild creatinine elevation (1.2 mg/dL) - these were warning signs that should have prompted lisinopril discontinuation 2
• Suspected dehydration was present but lisinopril was continued - this was an error, as volume depletion is a critical contraindication to continuing ACE inhibitors 1, 2
• Worsening BUN, creatinine, and potassium on repeat labs confirms progression of AKI 1, 3

The FDA label explicitly warns that lisinopril "can cause symptomatic hypotension, sometimes complicated by oliguria, progressive azotemia, acute renal failure or death" in patients with "severe volume and/or salt depletion of any etiology." 2

Immediate Management Steps

1. Discontinue Lisinopril Immediately

Stop lisinopril now - do not wait for further lab deterioration. 1, 2 The FDA label states to "consider withholding or discontinuing therapy in patients who develop a clinically significant decrease in renal function on lisinopril." 2 In the setting of volume depletion with rising creatinine and hyperkalemia, this is mandatory, not optional. 1

2. Stop All Diuretics

Discontinue any diuretic therapy immediately if the patient is on diuretics. 1 The European Society of Cardiology guidelines state: "If using concomitant loop and thiazide diuretic stop thiazide diuretic" and "reduce dose/stop loop diuretics if possible" when renal impairment occurs. 1

3. Volume Repletion

Restore intravascular volume with intravenous normal saline (250-500 mL boluses) to correct the dehydration. 3 The European Heart Journal recommends this approach for patients with volume depletion causing elevated BUN. 3 Volume expansion is the primary treatment for ACE inhibitor-induced acute renal failure in the setting of volume depletion. 4

4. Review All Medications

Check for and immediately discontinue any NSAIDs, which are the most common culprit of worsening renal function in this setting. 1, 3 NSAIDs combined with ACE inhibitors and volume depletion create a "triple whammy" for the kidneys. 1, 4

5. Address Hyperkalemia

Monitor potassium closely and treat if ≥5.5 mmol/L. 3, 5 The patient's potassium of 5.0 mmol/L was already borderline, and with worsening renal function it will likely rise further. 2 Stop any potassium supplements or potassium-sparing diuretics. 1, 2

Monitoring Protocol

Recheck serum creatinine, BUN, and potassium within 1-2 weeks after discontinuing lisinopril and restoring volume. 1, 3, 5 The renal dysfunction should be reversible once the ACE inhibitor is stopped and volume status is corrected. 4, 6

Critical Pitfall You Made

The major error was continuing lisinopril when dehydration was suspected. 1, 2 The FDA label explicitly lists "severe volume and/or salt depletion of any etiology" as a condition requiring very close medical supervision or avoidance of lisinopril. 2 When you suspected dehydration with a potassium of 5.0 and creatinine of 1.2, the correct action was to:

1. Stop the lisinopril immediately 1, 2
2. Restore volume status 3
3. Recheck labs in 1-2 weeks 1, 3
4. Only restart lisinopril after volume repletion and normalization of renal function, if still indicated 1, 4

Expected Clinical Course

The renal dysfunction should reverse within days to weeks after stopping lisinopril and correcting volume depletion. 4, 6 Research shows that ACE inhibitor-induced acute renal failure in volume-depleted patients is "reversible after withdrawal of the drug." 4 The creatinine should return toward baseline once angiotensin II-mediated efferent arteriolar tone is restored and volume status is corrected. 4, 6

When to Restart ACE Inhibitor Therapy

Do not restart lisinopril until:

• Volume status is fully restored 1, 3
• Creatinine returns to within 0.3 mg/dL of baseline 1
• Potassium is <5.0 mmol/L 3, 5
• Patient has adequate oral intake and is not at risk for recurrent dehydration 1

If ACE inhibitor therapy is still indicated after recovery, restart at a lower dose with close monitoring of renal function and potassium within 1-2 weeks. 1, 5 Consider whether the patient truly needs an ACE inhibitor or if alternative antihypertensive therapy would be safer. 1