Hyperkalemia

Background

• Defined as >6.0 mEq/L
• Consider pseudohyperkalemia (e.g. from hemolysis)
• Potassium secretion is proportional to flow rate and sodium delivery through distal nephron
  • Thua, loop & thiazide diuretics cause hypokalemia

Diagnosis

ECG

Changes NOT always predictable and sequential

• 6.5 - 7.5 mEq/L: peaked T waves, prolonged PR interval, shortened QT interval
• 7.5 - 8.0 mEq/L: widened QRS interval, flattened P waves
• 10 - 12 mEq/L: sine wave, ventricular fibrillation, heart block

Differential Diagnosis

1. Pseudohyperkalemia: hemolyzed specimen, prolonged tourniquet use prior to blood draw, thrombocytosis or leukocytosis
2. Redistribution (shift from intracellular to extracellular space)
   1. Acidemia (see DKA)
   2. Cellular breakdown: see Rhabdomyolysis/Crush Injury, hemolysis, see Tumor Lysis Syndrome
3. Increased total body potassium
   1. Inadequate excretion: Acute/chronic renal failure, Addison's disease, type 4 RTA
   2. Drug-induced: potassium-sparing diuretic (spironolactone), angiotensin converting enzyme inhibitors (ACE-I), nonsteroidal anti-inflammatory drugs (NSAIDs)
   3. Excessive intake: diet, blood transfusion
4. Other causes: succinylcholine, digitalis, beta-blockers

Treatment

Stabilize cardiac membranes

1. Indicated if there are any ECG changes or evidence of arrhythmias. Consider if K >7 mEq/L
2. Intravenous calcium only if QRS interval is prolonged
3. Can give as calcium gluconate or calcium chloride
   1. Calcium gluconate: Give 10ml of a 10% solution over 10 mins
      1. Only 1/3 the calcium compared to calcium chloride
      2. Can cause hypotension due to osmotic shift
   2. Calcium chloride 1 gram IV
      1. Give over 1 - 2 minutes
      2. Extravasation is bad: use a good IV
      3. Usually given in code situations
   3. Duration of action: 30 - 60 minutes
   4. Use caution in patients taking Digoxin although risk of Stone Heart may be unsubstantiated
   5. Do serial EKGs to track progress: may need to give multiple doses

Shift K+ intracellularly

1. Intravenous insulin + dextrose
   1. Give 10 units regular insulin intravenously with 25 to 50 grams (1 - 2 50 mL ampules) of 50% dextrose (D50)
      1. May withhold dextrose if blood sugar >300 mg/dl (>17 mmol/L)
      2. Duration of effect: 4 - 6 hours
2. Nebulized albuterol 5 - 20 mg
   1. Response is dose-dependent
   2. Peak effect: 30 minutes
   3. Duration of effect: 2 hours
3. Intravenous sodium bicarbonate 50 ml of 8.4% solution (1 ampoule) given over 5 minutes
   1. Duration of effect: 1 - 2 hours
   2. Generally not required, unless pH <7.1

Remove K+ from system

1. Intravenous furosemide (Lasix) 40 - 80 mg
   1. Ensure adequate urine output first
2. Sodium polystyrene sulfonate (Kayexylate): 30 gm oral or per rectum
   1. Controversial, see: EBQ: Use of Kayexylate in Hyperkalemia
3. Intravenous normal saline solution for volume expansion if dehydrated, rhabdomyolysis, diabetic ketoacidosis or other acidosis
4. Definitive treatment is hemodialysis

See Also

• Electrolyte Abnormalities (Main)
• Acute Renal Failure
• Crush Syndrome

External Links

• ECG Weekly -Hyperkalemia

Source

Tintinalli Management Severe Hyperkalemia. Crit Care Med, 2008, 36:12 EMCrit Podcast #32