A 62-year-old woman with type 2 diabetes mellitus on metformin 1000 mg BD and hypertension on lisinopril 10 mg daily presents with a 3-day history of acute gastroenteritis with persistent vomiting and diarrhoea. Her serum creatinine has risen from 0.8 mg/dL (baseline) to 1.6 mg/dL. She is haemodynamically stable but mildly dehydrated. What is the most appropriate immediate next step?

Question

Accepted Answer

A. Hold metformin and lisinopril; start intravenous fluids and reassess renal function in 48 hours. ## Clinical Context This patient has **acute kidney injury (AKI)** secondary to dehydration from gastroenteritis. The doubled serum creatinine reflects a significant drop in glomerular filtration rate (GFR). Two drugs require immediate action: **metformin** (lactic acidosis risk in renal failure) and **ACE inhibitor** (worsening renal perfusion). ## Why Metformin Must Be Held **Key Point:** Metformin is contraindicated in renal impairment (eGFR < 30 mL/min/1.73 m²) due to accumulation and risk of **metformin-associated lactic acidosis (MALA)**. In acute renal dysfunction, metformin must be held until renal function stabilizes. | Renal Function | Metformin Action | |---|---| | eGFR ≥ 45 | Use with caution; monitor | | eGFR 30–44 | Contraindicated; hold | | eGFR < 30 | Absolutely contraindicated | **High-Yield:** MALA is rare but fatal (mortality ~50%). Risk increases with renal impairment, dehydration, sepsis, and contrast exposure. ## Why ACE Inhibitors Must Be Held **Clinical Pearl:** ACE inhibitors reduce intraglomerular pressure by dilating the efferent arteriole. In acute dehydration and AKI, they can precipitate **acute tubular necrosis** or worsen renal perfusion. Holding the ACE inhibitor allows renal autoregulation to restore GFR as volume status improves. ## Management Algorithm for Drug-Induced AKI ```mermaid flowchart TD A[Acute rise in creatinine + dehydration]:::outcome --> B{Identify nephrotoxic drugs}:::decision B -->|Metformin| C[Hold metformin]:::action B -->|ACE-I/ARB| D[Hold ACE-I/ARB]:::action B -->|NSAIDs| E[Hold NSAIDs]:::action C --> F[IV fluids to restore volume]:::action D --> F E --> F F --> G[Recheck creatinine in 48-72 hrs]:::action G --> H{Creatinine improving?}:::decision H -->|Yes| I[Restart drugs cautiously]:::action H -->|No| J[Further investigation for AKI]:::action ``` ## Next Steps in This Patient 1. **Hold metformin** (risk of MALA in AKI) 2. **Hold lisinopril** (worsens renal perfusion in dehydration) 3. **IV fluids** (0.9% saline, 500 mL bolus, then maintenance based on urine output and vital signs) 4. **Antiemetics** (ondansetron 4–8 mg IV/PO) 5. **Recheck serum creatinine and electrolytes in 48 hours** 6. **Monitor urine output** (target > 0.5 mL/kg/hr) **Warning:** Do NOT continue metformin in AKI. Do NOT use NSAIDs or contrast agents until renal function recovers. ## Reinitiation Criteria - Serum creatinine returns to baseline or near-baseline - Oral intake is adequate - No ongoing diarrhoea or vomiting - eGFR is reassessed and documented [cite:KD Tripathi 8e Ch 13; Harrison 21e Ch 297]

Answer

B. Continue metformin and lisinopril; start intravenous fluids and antiemetics

Answer

C. Continue metformin at half dose; hold lisinopril; start intravenous fluids

Answer

D. Discontinue both drugs permanently and switch to insulin and amlodipine

Explanation

Clinical Context

Why Metformin Must Be Held

Why ACE Inhibitors Must Be Held

Management Algorithm for Drug-Induced AKI

Next Steps in This Patient

Reinitiation Criteria

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Renal Function	Metformin Action
eGFR ≥ 45	Use with caution; monitor
eGFR 30–44	Contraindicated; hold
eGFR < 30	Absolutely contraindicated