## Acute Management of Hyperkalemia: Mechanisms & Timing ### Three Categories of Intervention | Mechanism | Agent | Onset | Duration | Use Case | |-----------|-------|-------|----------|----------| | **Cardiac stabilization** | IV Ca²⁺ gluconate 10% | 1–3 min | 30–60 min | ECG changes (peaked T, widened QRS) | | **Shift K⁺ intracellularly** | Insulin + dextrose | 10–20 min | 4–6 hrs | Rapid reduction needed | | **Shift K⁺ intracellularly** | β₂-agonist (albuterol) | 30 min | 4–6 hrs | Adjunct to insulin | | **Shift K⁺ intracellularly** | NaHCO₃ | 30–60 min | 2–4 hrs | Metabolic acidosis present | | **Total body K⁺ removal** | Diuretics (loop) | 1–2 hrs | Depends on urine output | Preserved renal function | | **Total body K⁺ removal** | Cation exchange resin | 4–24 hrs | Slow, unreliable | Chronic management | | **Total body K⁺ removal** | Dialysis | Immediate | Definitive | Renal failure, severe K⁺ | **Key Point:** Sodium polystyrene sulfonate (Kayexalate) has **no role in acute hyperkalemia management**. It takes 4–24 hours to work, is unreliable, and causes constipation and GI necrosis (especially with sorbitol). It is used only for **chronic, mild hyperkalemia** in outpatient settings. ### Why This Patient Needs Immediate Action **High-Yield:** With K⁺ = 6.8 mEq/L and CKD stage 4, this patient is at imminent risk of cardiac arrhythmia. The management sequence is: 1. **Stabilize myocardium** → IV calcium gluconate (protects against dysrhythmia) 2. **Shift K⁺ into cells** → Insulin + dextrose (fastest intracellular shift) 3. **Add NaHCO₃** if metabolic acidosis present (acidosis worsens hyperkalemia by shifting K⁺ out of cells) 4. **Remove K⁺ from body** → Dialysis (definitive in CKD stage 4) or loop diuretics (if urine output preserved) **Clinical Pearl:** Kayexalate is a **chronic management agent**, not acute. In acute hyperkalemia, it delays definitive therapy and provides false reassurance. ### Why Kayexalate Fails in Acute Settings - Onset: 4–24 hours (too slow) - Efficacy: Unpredictable, ~1 mEq/L reduction per dose - Mechanism: Binds K⁺ in colon; requires intact GI transit - Complications: Colonic necrosis, especially with sorbitol co-formulation (now avoided) - Evidence: No RCT support for acute use; included in many older guidelines but **de-emphasized in current practice** [cite:Harrison 21e Ch 280]
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