Renal · Year 2 · from Renal
Case 2: Hyperkalemia in Diabetic Kidney Disease
Patient Presentation
A 62-year-old male with type 2 diabetes and stage 4 CKD (eGFR 22 mL/min) presents to the emergency department after his cardiologist noted "tall T waves" on a routine ECG. He reports no symptoms.
History of Present Illness
- Routine cardiology follow-up for stable coronary artery disease
- ECG changes prompted immediate ED referral
- No chest pain, palpitations, or weakness
- Medications: lisinopril 20 mg, metoprolol 50 mg, spironolactone 25 mg, empagliflozin 10 mg
- Recently started on ibuprofen 600 mg TID for knee osteoarthritis
Physical Examination
- Blood pressure: 142/88 mmHg
- Heart rate: 58 bpm, regular
- No peripheral edema
- Normal strength throughout
- Alert and oriented
Workup
Laboratory Studies:
- Serum potassium: 6.8 mEq/L (severely elevated)
- Creatinine: 2.8 mg/dL (baseline 2.4)
- BUN: 48 mg/dL
- Bicarbonate: 18 mEq/L (low - metabolic acidosis)
- Glucose: 168 mg/dL
ECG:
- Peaked, narrow T waves
- PR interval 240 ms (prolonged)
- QRS 110 ms (borderline widened)
- No P wave loss or sine wave pattern
Diagnosis
Severe Hyperkalemia due to Type 4 RTA and Multiple Contributing Medications
Discussion
This case demonstrates multiple mechanisms of hyperkalemia:
- Type 4 RTA (Hyporeninemic Hypoaldosteronism): Common in diabetic nephropathy. The lecture explains that hyperkalemia inhibits renal ammoniagenesis, reducing net acid excretion and causing the mild metabolic acidosis typical of type 4 RTA.
- Medication Contributions: Multiple drugs that raise potassium - lisinopril (ACE inhibitor reduces aldosterone), spironolactone (blocks mineralocorticoid receptor), metoprolol (beta-blocker impairs cellular potassium uptake), ibuprofen (NSAID reduces prostaglandin-mediated renin release and directly affects potassium secretion).
- ECG Changes: The lecture describes the progression of ECG changes - peaked T waves appear first (5.5-6.5 mEq/L), followed by PR prolongation and QRS widening (6.5-7.5 mEq/L).
- Pseudohyperkalemia Excluded: The patient has no hemolysis, thrombocytosis, or leukocytosis, and ECG changes confirm true hyperkalemia.
Treatment
Immediate Management:
- Calcium gluconate 10 mL of 10% IV over 2-3 minutes (membrane stabilization)
- Regular insulin 10 units IV with 25 g dextrose (shift potassium intracellularly)
- Sodium bicarbonate 50 mEq IV for the acidosis
- Continuous cardiac monitoring
Subsequent Management:
- Discontinue spironolactone and ibuprofen
- Hold lisinopril temporarily
- Sodium polystyrene sulfonate 30 g orally
- Consider dialysis if refractory
- Potassium-restricted diet
Clinical Pearl
The combination of ACE inhibitor, mineralocorticoid receptor antagonist, and NSAID in a patient with CKD and diabetes represents a "perfect storm" for hyperkalemia. Each medication alone may be tolerated, but together they can precipitate life-threatening hyperkalemia.