Hyperkalemia

A hyperkalemia is defined as a blood potassium concentration > 5 mmol/l, subject to the specific standards of the reference laboratory. It is the most serious of electrolyte disorders.

Clinical Presentation

Hyperkalemia is more symptomatic when it develops rapidly. Symptoms may include paresthesia, weakness, hyperreflexia followed by hyporeflexia, confusion, and potentially fatal arrhythmias (ventricular fibrillation and asystole). ECG findings may include QRS widening (++ at > 7.5 mmol/l), P wave flattening, ST depression, and tall T waves.

Hyperkalemia becomes critical (an emergency) at > 6 mmol/l, with imminent risk of cardiac arrest at > 7 mmol/l. Associated hypocalcemia is an aggravating factor.

Additional Tests

• ECG: tall T waves, QRS widening, atrioventricular blocks (AVB), bundle branch blocks, bradycardia, ectopic beats, VF, asystole
• Blood tests: electrolytes, CK and LDH (cytolysis), creatinine (renal failure), complete blood count
• Urine electrolytes
• Blood gas analysis: acidosis?
• ACTH test: cortisol levels → 250 microg IV → cortisol levels after 1 hour (Addison's disease: response < 8 microg/dl)

Etiologies

The most common causes are by far acute or chronic kidney failure, cellular lysis (++ in rhabdomyolysis), acidosis, and iatrogenic causes (potassium-sparing diuretics, beta-blockers, ACE inhibitors, heparin, NSAIDs, excessive potassium intake). Hypoaldosteronism should also be considered, and pseudo-hyperkalemia (due to hemolysis in the sample tube, overly tight tourniquet, or rapid aspiration) must be excluded.

Therapeutic Management - Symptomatic Treatments

If K+ is between 5 and 6 mmol/l:

• Discontinue all potassium intake and implement a low potassium diet
• Ion-exchange resins: 15-30 g (1-2 spoonfuls) of sodium or calcium kayexalate orally every 2 hours (~3x)

If K+ > 6 mmol/l or ECG abnormalities: EMERGENCY! Notify an intensivist and combine the following approaches (Calcium and bicarbonate act within the first hour):

• Low potassium diet
• Insulin: 10-20 U Actrapid + 50 ml of 50% glucose or 500 cc of 10% glucose IV over 15 minutes, repeat as necessary
• Sodium bicarbonate 50-100 mEq IV (! indicated ++ in metabolic acidosis, contraindications: alkalosis, hypernatremia, oligoanuria, hypertension)
• Ion-exchange resins: 15-30 g sodium or calcium kayexalate orally every 2 hours (~3x)
• 1 g calcium gluconate or chloride IV over 2-5 minutes, repeat after 5-10 minutes if necessary
• Salbutamol IV 0.5-2 mg in 500 cc of 5% glucose over 15 minutes
• Hemodialysis if severe deterioration, renal failure, or refractory life-threatening hyperkalemia
• If renal function is preserved: aggressive fluid replacement + high-dose IV furosemide
• Monitoring, consider transfer to ICU

Bibliography

EMC, Traité de néphrologie, Elsevier, 2018

Longo DL et al., Harrison - Principes de médecine interne, 18e éd., Lavoisier, 2013