What medication should be discontinued in a diabetic (diabetes mellitus), hypertensive, and chronic heart failure patient with deep vein thrombosis (DVT) on insulin, furosemide (Lasix), and enalapril (Angiotensin-Converting Enzyme (ACE) inhibitor) with hyperkalemia (elevated potassium level of 6.0 mmol/L)?

Enalapril Should Be Discontinued

In this patient with severe hyperkalemia (6.0 mmol/L), elevated creatinine (120 μmol/L), and diabetes mellitus on triple therapy with enalapril, furosemide, and heparin for DVT, enalapril must be discontinued immediately as it is the primary driver of the life-threatening hyperkalemia. 1, 2

Why Enalapril Must Be Stopped

Direct Mechanism of Hyperkalemia

• ACE inhibitors like enalapril block angiotensin II production, which reduces aldosterone secretion and directly impairs renal potassium excretion 2, 3
• The FDA label explicitly warns that enalapril "attenuates potassium loss" and that potassium-sparing agents should "generally not be used in patients with heart failure receiving enalapril" 2
• This patient's potassium of 6.0 mmol/L represents severe hyperkalemia requiring immediate intervention 1, 4

Amplified Risk in This Patient

• Diabetes mellitus independently amplifies hyperkalemia risk with ACE inhibitors, regardless of renal function 1, 3
• The ATMOSPHERE trial showed that diabetic heart failure patients on enalapril had severe hyperkalemia (>6.0 mmol/L) rates approaching 4% over 27 months, with real-world rates likely higher 1
• Elevated creatinine (120 μmol/L, above normal 44-115) indicates renal impairment, which further increases hyperkalemia risk 1, 5
• The combination of diabetes, renal insufficiency, and heart failure creates a "perfect storm" for ACE inhibitor-induced hyperkalemia 6, 5

Evidence-Based Discontinuation Strategy

• The American Heart Association guidelines recommend holding ACE inhibitors temporarily until potassium falls below 5.0 mmol/L 4
• Patients with serum urea nitrogen >6.4 mmol/L (this patient has 7.9 mmol/L) and creatinine >136 μmol/L are independently associated with ACE inhibitor-induced hyperkalemia 5
• Once hyperkalemia is controlled and concurrent conditions stabilize, enalapril can be cautiously reintroduced at low doses with intensive monitoring 1, 4

Why Other Medications Should Continue

Insulin (Option A) - Continue

• Insulin is safe in renal impairment and is actually used therapeutically to treat hyperkalemia by shifting potassium intracellularly 1, 4
• The American Heart Association states insulin may require lower doses with reduced eGFR but remains safe 1
• Stopping insulin would worsen diabetic control without addressing the hyperkalemia 1

Heparin (Option C) - Continue

• Active DVT requires continued anticoagulation to prevent life-threatening pulmonary embolism 2
• The APTT of 50 seconds (therapeutic range 30-40) indicates adequate anticoagulation that may need minor adjustment, not discontinuation 2
• Heparin does not cause hyperkalemia 2, 3

Furosemide (Option D) - Continue and Likely Increase

• Loop diuretics like furosemide actually reduce hyperkalemia risk by promoting renal potassium excretion 2, 7
• The FDA label states "enalapril attenuates potassium loss caused by thiazide-type diuretics," implying diuretics counteract ACE inhibitor hyperkalemia 2
• Diabetic heart failure patients require higher furosemide doses, with an independent 26% higher odds of needing ≥80 mg daily 8
• This patient's elevated urea (7.9 mmol/L) and creatinine suggest volume overload requiring continued or intensified diuretic therapy 8

Immediate Management Algorithm

Step 1: Discontinue Enalapril

• Stop enalapril immediately 1, 4, 2
• Document reason as severe hyperkalemia with diabetes and renal impairment 1

Step 2: Acute Hyperkalemia Treatment

• Administer IV calcium gluconate 10% (15-30 mL) over 2-5 minutes for cardiac membrane stabilization 4
• Give 10 units regular insulin IV with 50 mL D50W to shift potassium intracellularly 4
• Consider nebulized albuterol 10-20 mg to lower potassium by 0.5-1.0 mEq/L 4
• Increase furosemide to 40-80 mg IV to eliminate potassium renally 4, 8

Step 3: Monitoring Protocol

• Check potassium every 2-4 hours until stable below 5.5 mmol/L 4
• Continuous cardiac monitoring for at least 6 hours 4
• Reassess renal function within 24 hours 4

Step 4: Long-Term Management

• Reinitiate enalapril only after potassium <5.0 mmol/L, starting at lowest dose (2.5 mg daily) 1, 4
• Monitor potassium within 1 week after restarting 4
• Educate patient to avoid potassium supplements, salt substitutes, and NSAIDs 1, 2
• Consider potassium binder therapy (patiromer or zirconium cyclosilicate) if chronic hyperkalemia develops 3

Critical Pitfalls to Avoid

Do Not Stop Furosemide

• Discontinuing diuretics paradoxically worsens hyperkalemia by reducing renal potassium excretion 2, 7
• Studies show concurrent loop diuretics are associated with reduced hyperkalemia risk in ACE inhibitor users 5

Do Not Continue Enalapril "Because Guidelines Recommend It"

• While ACE inhibitors improve heart failure outcomes, continuing them during severe hyperkalemia (6.0 mmol/L) risks fatal arrhythmias 3, 6
• Temporary discontinuation is safer than risking sudden cardiac death 6
• Discontinuing RAAS inhibitors for hyperkalemia is associated with increased mortality, but so is uncontrolled hyperkalemia—the key is temporary discontinuation with planned reinitiation 3, 6

Monitor for Rebound After Acute Treatment

• Insulin and albuterol effects last only 4-6 hours and 2-4 hours respectively, with possible rebound hyperkalemia 4
• Furosemide provides sustained potassium elimination 4, 8

The correct answer is B: Enalapril must be discontinued.