A 58-year-old man with CKD stage 4 (eGFR 22 mL/min/1.73m²) and type 2 diabetes presents to the emergency department with palpitations and muscle weakness. ECG shows peaked T waves and prolonged PR interval. Serum potassium is 7.2 mEq/L. He is haemodynamically stable with normal sinus rhythm. What is the most appropriate immediate next step in management?

Explanation

## Clinical Assessment This patient has **symptomatic hyperkalemia with ECG changes** (peaked T waves, prolonged PR interval) indicating **cardiac membrane instability**. Although haemodynamically stable, ECG abnormalities mandate immediate cardioprotection regardless of haemodynamic status. ## Management Algorithm for Hyperkalemia ```mermaid flowchart TD A[Hyperkalemia diagnosed]:::outcome --> B{ECG changes present?}:::decision B -->|Yes| C[Cardiac membrane instability]:::urgent C --> D[IV Calcium gluconate 10%<br/>10 mL over 2-5 min]:::action D --> E[Stabilize cardiac membrane]:::outcome E --> F[Shift K+ intracellularly:<br/>Insulin + glucose, beta-2 agonist]:::action F --> G[Remove K+ from body:<br/>Diuretics, dialysis, binders]:::action B -->|No| H[No immediate cardiac risk]:::outcome H --> F ``` ## Rationale for Calcium Gluconate **Key Point:** Calcium gluconate is the **first-line emergency intervention** for hyperkalemia with ECG changes. It does NOT lower serum potassium but **stabilizes the cardiac cell membrane** by raising the threshold potential, preventing arrhythmias and sudden cardiac death. **High-Yield:** - **Onset:** 1–3 minutes (fastest acting) - **Duration:** 30–60 minutes - **Mechanism:** Antagonizes K⁺ effect on cardiac excitability - **Dose:** 10 mL of 10% solution IV over 2–5 minutes; may repeat once after 5 minutes if ECG changes persist ## Subsequent Steps (After Calcium) | Intervention | Mechanism | Onset | Duration | K⁺ Reduction | |---|---|---|---|---| | **Insulin 10 U + Dextrose 25 g IV** | Shift K⁺ into cells | 10–20 min | 4–6 hours | 0.5–1.2 mEq/L | | **Salbutamol 10–20 mg nebulised** | β₂-adrenergic shift | 30 min | 2–4 hours | 0.5–1 mEq/L | | **Sodium bicarbonate 50 mEq IV** | Alkalinization (if acidotic) | 30–60 min | 2–4 hours | 0.5–1 mEq/L | | **Haemodialysis** | K⁺ removal from body | Immediate | Ongoing | 1–2 mEq/L per hour | | **Sodium polystyrene sulfonate** | GI K⁺ binding | 4–24 hours | Prolonged | 0.5–1 mEq/L | **Clinical Pearl:** In this patient with CKD stage 4, haemodialysis will eventually be needed, but calcium gluconate MUST be given first to prevent sudden death from arrhythmia during the time it takes to initiate dialysis. ## Why Calcium Gluconate First? **Mnemonic: ABCDE of Hyperkalemia Management** - **A** = Assess ECG (peaked T, prolonged PR, widened QRS) - **B** = **Calcium** (membrane stabilization) - **C** = Cellular shift (insulin, β₂-agonist, bicarbonate) - **D** = Diuretics (if volume overloaded) - **E** = Excretion (dialysis, binders) [cite:Harrison 21e Ch 280]