A 58-year-old man with chronic kidney disease stage 4 (eGFR 22 mL/min/1.73m²) presents to the emergency department with palpitations and mild dyspnea. He was started on lisinopril 10 mg daily 2 weeks ago for hypertension. On examination, blood pressure is 148/92 mmHg, heart rate 88 bpm with irregular rhythm. Serum potassium is 6.8 mEq/L, creatinine 3.2 mg/dL, pH 7.32, HCO₃⁻ 18 mEq/L. ECG shows peaked T waves in precordial leads and prolonged PR interval. What is the most appropriate immediate intervention?

Explanation

## Clinical Context This patient presents with symptomatic hyperkalemia (K⁺ 6.8 mEq/L) with ECG changes (peaked T waves, prolonged PR interval) indicating cardiac membrane instability. The etiology is multifactorial: CKD stage 4 with reduced renal excretion, ACE inhibitor use (reduces aldosterone-mediated K⁺ excretion), and likely metabolic acidosis (pH 7.32, HCO₃⁻ 18). ## Immediate Management Hierarchy **Key Point:** ECG changes (peaked T waves, PR prolongation, widened QRS) indicate cardiac toxicity and demand immediate stabilization of the myocardial membrane before shifting K⁺ intracellularly or removing it from the body. ### Step 1: Membrane Stabilization (First-line for ECG changes) | Agent | Mechanism | Onset | Duration | Dose | |-------|-----------|-------|----------|------| | **Calcium gluconate 10%** | Raises threshold potential, antagonizes K⁺ effect on membrane | 1–3 min | 30–60 min | 10 mL IV over 2–5 min | | **Calcium chloride 10%** | Same as above (faster onset, more irritating) | 1–2 min | 30–60 min | 5–10 mL IV | **Clinical Pearl:** Calcium does NOT lower K⁺ — it buys time by stabilizing the cardiac membrane, preventing arrhythmias and cardiac arrest while other therapies work. ### Step 2: Shift K⁺ Intracellularly (After membrane stabilization) - **Insulin + dextrose:** Shifts K⁺ into cells; onset 10–20 min, duration 4–6 hours - **Beta-2 agonists (salbutamol):** Activate Na⁺-K⁺-ATPase; onset 30 min - **Sodium bicarbonate:** In acidosis (pH < 7.2); onset 30–60 min ### Step 3: Remove K⁺ from Body - **Diuretics (furosemide):** Only if euvolemic and renal function permits - **Cation exchange resins (sodium polystyrene sulfonate):** Slow onset (4–24 hours); NOT for acute symptomatic hyperkalemia - **Hemodialysis:** Definitive removal; indicated if refractory or K⁺ > 7 mEq/L with ECG changes ## Why This Answer **High-Yield:** The presence of ECG changes (peaked T waves, PR prolongation) mandates immediate calcium administration. This is a "life-saving" intervention that stabilizes the myocardium and prevents sudden cardiac death while other measures take effect. **Mnemonic: CIKI** — **C**alcium (membrane), **I**nsulin + dextrose (shift), **K**idney removal (dialysis), **I**on exchange (slow). ## Sequence in This Case 1. **Calcium gluconate 10 mL IV** (immediate — membrane stabilization) 2. **Insulin 10 units + dextrose 25 g IV** (within 5 min — shift K⁺ in) 3. **Sodium bicarbonate 50 mEq IV** (metabolic acidosis present; shifts K⁺ in) 4. **Furosemide 40–80 mg IV** (if euvolemic) 5. **Hemodialysis** (if K⁺ remains > 6.5 or recurs; CKD stage 4 will need it) [cite:Harrison 21e Ch 280]