## Clinical Context This patient has **symptomatic hyperkalemia with ECG changes** (peaked T waves, prolonged PR interval) and **metabolic acidosis** (pH 7.32), which worsens hyperkalemia by shifting K⁺ out of cells. The combination of CKD stage 4, ACE inhibitor use, and diabetes creates a high-risk setting for life-threatening hyperkalemia. ## Mechanism of ECG Changes **Key Point:** Peaked T waves and PR prolongation indicate **cardiac membrane instability** — a medical emergency. Hyperkalemia depolarizes the resting membrane potential, increasing automaticity and conduction delays. This can progress to ventricular fibrillation without immediate intervention. ## Immediate Management Algorithm ```mermaid flowchart TD A[Serum K⁺ > 6.5 mEq/L + ECG changes]:::urgent --> B{Cardiac membrane stabilization needed?}:::decision B -->|Yes: peaked T, PR prolongation| C[IV Calcium gluconate 10% immediately]:::action B -->|No ECG changes| D[Shift K⁺ intracellularly]:::action C --> E[Calcium stabilizes cardiac membrane in 1-3 min]:::outcome E --> F[Then shift K⁺: insulin + glucose, beta-2 agonist]:::action D --> F F --> G[Remove K⁺: diuretics, cation exchangers, dialysis]:::action ``` ## Why Calcium Gluconate First **High-Yield:** Calcium **does NOT lower serum K⁺** — it **stabilizes the cardiac membrane** and buys time (1–3 minutes effect) for other therapies to work. In the presence of ECG changes, this is the **only life-saving first step**. - **Dose:** 10 mL of 10% solution IV over 2–3 minutes (or 5–10 mL of 10% solution) - **Onset:** 1–3 minutes - **Duration:** 30–60 minutes - **Mechanism:** Increases the threshold potential, opposing hyperkalemia-induced depolarization **Clinical Pearl:** If ECG changes are present, calcium gluconate must be given **before** or **concurrent with** potassium-shifting agents. Delaying calcium to give insulin first risks cardiac arrest. ## Subsequent Steps (After Calcium) | Agent | Mechanism | Onset | Duration | Dose | |-------|-----------|-------|----------|------| | **Insulin + glucose** | Shift K⁺ into cells via Na⁺-K⁺-ATPase | 10–20 min | 4–6 hrs | 10 U regular IV + 25 g dextrose | | **Albuterol** (salbutamol) | β₂-agonist; shift K⁺ intracellularly | 30 min | 2–4 hrs | 10–20 mg nebulized | | **Sodium bicarbonate** | Useful in acidosis (as here, pH 7.32) | 30–60 min | 2 hrs | 50–100 mEq IV | | **Diuretics** (furosemide) | Remove K⁺ via urine (if urine output adequate) | 1–2 hrs | Variable | 40–80 mg IV | | **Cation exchangers** (sodium polystyrene) | Remove K⁺ via GI tract | 4–24 hrs | Slow | 15 g PO/PR | | **Hemodialysis** | Definitive removal; for refractory or severe cases | Immediate | Complete | Urgent if K⁺ > 7 or refractory | ## Why This Patient Needs Dialysis Eventually With **eGFR 22 mL/min/1.73 m²**, this patient has **severely reduced renal K⁺ excretion**. After medical stabilization, **hemodialysis is indicated** because: - ACE inhibitor (lisinopril) blocks aldosterone → K⁺ retention - Diabetes + CKD = hyperreninemic hypoaldosteronism - Metabolic acidosis worsens hyperkalemia - Medical therapy alone will not prevent recurrence **Warning:** Sodium polystyrene sulfonate is **slow** (4–24 hours) and **not appropriate as first-line** in symptomatic hyperkalemia. It is useful for **chronic management** or **mild asymptomatic hyperkalemia** but should never delay calcium or insulin in an emergency. ## Summary: The Sequence 1. **Calcium gluconate** → stabilize heart (1–3 min) 2. **Insulin + glucose + albuterol** → shift K⁺ in (10–30 min) 3. **Sodium bicarbonate** → correct acidosis (helps shift K⁺ in) 4. **Diuretics** → remove K⁺ via urine 5. **Hemodialysis** → definitive removal (arrange urgently) [cite:Harrison 21e Ch 280]
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