🫀 Chapter 94: Potassium Disorders (Hyperkalemia & Hypokalemia)

Hyperkalemia: ECG (peaked T, wide QRS, sine wave) · Treatment (calcium, insulin+glucose, albuterol, kayexalate, dialysis) · Pseudohyperkalemia · Hypokalemia: ECG (U waves, flat T) · Causes · KCl replacement (IV central line preferred, max 0.5-1 mEq/kg/h)

🔍 Core Concepts: Potassium Disorders

📌 Hyperkalemia (>5 mEq/L)
ECG: peaked T waves → wide QRS → loss P wave → sine wave → VF/asystole. Acute treatment: calcium (stabilises membrane), insulin+glucose, albuterol (shifts K into cells), kayexalate/dialysis (removal).
⚠️ Pseudohyperkalemia
In vitro haemolysis, tourniquet use, severe leukocytosis/thrombocytosis. No ECG changes. Repeat sample to confirm.
📉 Hypokalemia (<3.6 mEq/L)
ECG: flat T waves, U waves, ST depression, prolonged QT. Causes: vomiting, diarrhoea, diuretics, mineralocorticoid excess, alkalosis. Treatment: KCl (IV or oral).
💊 KCl Replacement (IV)
Max rate 0.5-1 mEq/kg/h (prefer central line). Concentration ≤60 mEq/L (peripheral), ≤80 mEq/L (large vein). ECG monitoring. 1 mEq/kg raises K ~1 mEq/L.
⚖️ Acid-base effect
Every 0.1 drop in pH (acute metabolic acidosis) increases serum K by 0.3-1.3 mEq/L. Alkalosis lowers K.
🧪 Causes of Hyperkalemia
Redistribution (acidosis, digoxin, succinylcholine, beta-blockers). Decreased excretion (renal failure, ACE inhibitors, spironolactone). Increased load (haemolysis, transfusion, tumour lysis).

🩺 Stepwise Approach: Hyperkalemia Emergency

1
Confirm true hyperkalemia (ECG, repeat sample)
Check for pseudohyperkalemia (haemolysis, tourniquet). ECG: peaked T waves earliest sign. If ECG changes or K >6.5-7 → treat emergently.
2
Stabilise myocardium (calcium)
Give 10% calcium gluconate 0.3-0.5 mL/kg IV over 2-5 min (max 20 mL). Calcium chloride (3x more calcium) via central line. Onset seconds, duration 30-60 min.
3
Shift K into cells (temporary)
Insulin (0.1 U/kg) + dextrose (1 g/kg) over 1 hour. Nebulised albuterol (0.05 mL/kg of 5 mg/mL solution). Sodium bicarbonate (1-2 mEq/kg) if acidosis present.
4
Remove K from body (definitive)
Kayexalate (sodium polystyrene sulfonate) 1 g/kg PR/PO. Loop diuretics (furosemide 1-2 mg/kg) if renal function ok. Haemodialysis is most effective (15-30 min onset).
5
Hypokalemia management
Mild-moderate: oral KCl. Severe (<2.5 mEq/L) or symptomatic: IV KCl 0.5-1 mEq/kg/h (max 0.5 mEq/kg/h peripheral, 1 mEq/kg/h central). Monitor ECG, K q2-4h.
6
Monitor & adjust
Repeat K after each intervention. Avoid kayexalate in post-op/immunocompromised (bowel necrosis risk). Treat underlying cause (stop offending drugs, correct acidosis).