Which medication should be stopped in an elderly patient with hypertension, diabetes type 2, and DVT on metformin, atorvastatin, lisinopril, furosemide, and heparin, with hyperkalemia and prolonged PT and APTT?

Lisinopril Should Be Stopped Immediately

In this elderly patient with hyperkalemia (K+ 6.0 mEq/L) and declining renal function (Cr 120 μmol/L), lisinopril must be discontinued immediately as it is the primary cause of the hyperkalemia. 1, 2

Rationale for Stopping Lisinopril (Answer C)

Hyperkalemia Mechanism and Severity

• Potassium of 6.0 mEq/L represents moderate-to-severe hyperkalemia requiring immediate intervention 1, 2
• ACE inhibitors like lisinopril cause hyperkalemia by blocking angiotensin II-mediated aldosterone release, reducing renal potassium excretion 1
• The European Society of Cardiology recommends discontinuing RAAS inhibitors immediately when K+ >6.5 mEq/L, and this patient at 6.0 mEq/L is approaching this critical threshold 1, 2
• The American College of Cardiology identifies discontinuing ACE inhibitors as the primary intervention in moderate hyperkalemia with declining renal function 1, 2

High-Risk Patient Profile

• Elderly diabetic patients on ACE inhibitors have significantly increased hyperkalemia risk, particularly with declining renal function 1
• This patient has multiple risk factors: advanced age, diabetes type 2, declining renal function (Cr 120→115 μmol/L suggests worsening), and concurrent diuretic use 3, 1
• The combination of ACE inhibitor with diabetes and renal insufficiency creates a particularly dangerous scenario for hyperkalemia 3, 4

Why Other Medications Should NOT Be Stopped

Heparin (Option A) - Continue

• Heparin is essential for treating the acute DVT and cannot be stopped 5
• While heparin can cause hyperkalemia through aldosterone suppression, this typically occurs only with prolonged use (>7 days) and is far less pronounced than ACE inhibitor-induced hyperkalemia 1, 2, 4
• The patient was just started on heparin for acute DVT, making it an unlikely cause of the current hyperkalemia 4
• The prolonged PT/APTT is expected with therapeutic heparin and does not indicate toxicity requiring discontinuation 6

Furosemide (Option B) - Continue

• Loop diuretics like furosemide actually reduce hyperkalemia risk by promoting urinary potassium excretion and should be continued 1, 2
• The European Society of Cardiology recommends continuing thiazide/loop diuretics to promote potassium excretion and help lower serum potassium 2
• Stopping furosemide would worsen hyperkalemia and potentially cause volume overload 3

Metformin (Option D) - Continue

• Metformin does not cause hyperkalemia and has no direct effect on potassium homeostasis 1, 2
• Metformin is safe to continue with eGFR ≥30 mL/min/1.73 m² 3
• While metformin requires monitoring in renal insufficiency due to lactic acidosis risk, the current creatinine level does not mandate discontinuation 3
• Metformin should be temporarily held only if acute kidney injury develops or before contrast procedures 3

Immediate Management Steps

Acute Intervention

• Discontinue lisinopril immediately 1, 2
• Obtain ECG to assess for hyperkalemia-related cardiac changes (peaked T waves, widened QRS) 2
• Recheck potassium and creatinine within 24-48 hours after stopping lisinopril 2

If Potassium Remains Elevated

• If K+ remains >5.5 mEq/L after stopping lisinopril, initiate sodium zirconium cyclosilicate or patiromer 2
• Avoid sodium polystyrene sulfonate (Kayexalate) in elderly patients due to serious gastrointestinal adverse events including colonic necrosis 2

Long-Term Blood Pressure Management

• Once potassium normalizes to 4.0-5.0 mEq/L, consider alternative antihypertensive agents that do not affect potassium homeostasis 2
• Calcium channel blockers (such as amlodipine) are preferred alternatives in this setting 2
• If cardio-renal protection from RAAS inhibition is essential, newer potassium binders can enable reintroduction of lisinopril at lower doses with close monitoring 2

Common Pitfalls to Avoid

• Do not continue ACE inhibitors hoping the hyperkalemia will resolve spontaneously - this can lead to life-threatening cardiac arrhythmias 1
• Do not stop heparin for DVT treatment - the hyperkalemia is not primarily heparin-induced given the short duration of therapy 4
• Do not discontinue furosemide - this will worsen hyperkalemia and is counterproductive 2
• Do not use older potassium binders like Kayexalate in elderly patients - they carry significant GI toxicity risk 2