A 58-year-old man with type 2 diabetes mellitus and chronic kidney disease (eGFR 22 mL/min/1.73 m²) presents to the emergency department with palpitations and generalized weakness for 2 days. He has been taking lisinopril 10 mg daily and spironolactone 25 mg daily for hypertension and proteinuria. On examination, blood pressure is 148/92 mmHg, heart rate 102/min and irregular. ECG shows peaked T waves, prolonged PR interval, and widened QRS complex. Serum potassium is 7.8 mEq/L, sodium 138 mEq/L, creatinine 3.2 mg/dL, and pH 7.28. What is the most appropriate immediate intervention?

Explanation

## Clinical Context This patient presents with **symptomatic hyperkalemia** (K⁺ 7.8 mEq/L) with **ECG changes indicating cardiotoxicity** (peaked T waves, prolonged PR interval, widened QRS). The underlying cause is **reduced renal excretion** (CKD stage 4) compounded by **ACE inhibitor and aldosterone antagonist** use. ## Management Hierarchy in Symptomatic Hyperkalemia **Key Point:** Treatment priority depends on the presence of **cardiac manifestations**. With ECG changes, the sequence is: 1. **Cardiac membrane stabilization** (calcium salts) — immediate 2. **Intracellular shift** (insulin + glucose, β₂-agonists, bicarbonate in acidosis) 3. **Removal** (diuretics, cation exchangers, dialysis) ## Why Calcium Gluconate First? **High-Yield:** Intravenous calcium (10 mL of 10% calcium gluconate IV over 2–5 minutes) **does NOT lower K⁺** but **antagonizes the cardiac effects** of hyperkalemia by: - Restoring the negative membrane potential - Reducing the threshold potential - Preventing arrhythmias and cardiac arrest This is a **life-saving temporizing measure** that must precede all other interventions when ECG changes are present. ## Subsequent Management After calcium stabilization: - **Insulin 10 units IV + 25 g dextrose** shifts K⁺ intracellularly within 10–20 minutes - **Salbutamol nebulized** (if available) provides additional intracellular shift - **Sodium bicarbonate 50 mEq IV** (indicated here because pH 7.28 = metabolic acidosis, which worsens hyperkalemia) - **Definitive removal:** Hemodialysis is the gold standard for CKD patients with refractory hyperkalemia ## Medication Adjustment **Clinical Pearl:** Lisinopril and spironolactone must be **discontinued** in this patient (CKD + hyperkalemia is a contraindication to RAAS inhibitors). However, this is a **chronic measure**, not an acute intervention. | Intervention | Onset | Duration | Mechanism | |---|---|---|---| | **Calcium gluconate** | 1–3 min | 30–60 min | Membrane stabilization | | **Insulin + glucose** | 10–20 min | 4–6 hrs | Intracellular shift | | **Bicarbonate** | 30–60 min | 2–4 hrs | Intracellular shift (in acidosis) | | **Cation exchanger** | Hours | Days | Fecal removal | | **Hemodialysis** | Immediate | Permanent | Extracorporeal removal | **Mnemonic:** **CHIME** — **C**alcium (stabilize), **H**yperventilation/bicarb (shift), **I**nsulin (shift), **M**edicine (remove), **E**xcretion (dialysis). [cite:Harrison 21e Ch 280]