Hyperkalemia

Introduction 

Hyperkalemia is an electrolyte abnormality with adverse clinical outcome or death if not treated properly. 

Most patients with hyperkalemia slightly over 5 mmol/l are asymptomatic. When present, symptoms are nonspecific and predominantly related to muscular or cardiac function. 

Hyperkalemia can result from any of the following reasons, which often occur in combination:

  • Excessive intake
  • Decreased excretion
  • A shift of potassium from the intracellular to the extracellular space

Hyperkalemia = potassium level > 5.5 mmol/l

Moderate hyperkalemia > 6.0 mmol/l

Severe hyperkalemia > 7.0 mmol/l


ECG manifestation

ECG findings generally correlate with the potassium level, but potentially life-threatening arrhythmias can occur without warning at almost any level of hyperkalemia.

Early ECG changes of hyperkalemia (5.5-6.5mmol/l)

  • Tall, peaked T waves with a narrow base, best seen in precordial leads 
  • Shortened QT interval

  ECG changes if blood potassium is 6.5-8.0 mmol/l

  • Peaked T waves
  • Prolonged PR interval
  • Decreased or disappearing P wave
  • Widening of the QRS
  • ST elevations that can mimic STEMI / ST depressions 

 At a serum potassium level higher than 8.0 mmol/l, the ECG shows the following

  • Absence of P waves
  • Progressive QRS widening
  • Intraventricular/fascicular/bundle branch blocks
  • asystoly
  • ventricular fibrillation

Sensitivity of ECG changes is not very high - 34-43%, but specificity is about 85%. 

!! Suspect hyperkalaemia in any patient with a new bradyarrhythmia or AV block, especially patients with renal failure, on haemodialysis or taking any combination of ACE inhibitors, potassium-sparing diuretics and potassium supplements.

ECG 1 Hyperkalemia 6.5 mmol/l in a patient with chronic renal failure (slight ST elevations in I, II, avL, peaked T waves in I, II, aVF, V2-V6) 

 

ECG 2A Iatrogenic hyperkalemia in a patient with renal failure (wide QRS complexes, ST deviations, peaked  waves)

ECG 50 mm/s
 

ECG 2B ECG of the same patient after reverting hyperkalemia 

 

Management

 The aggressiveness of therapy is directly related to the rapidity with which hyperkalemia has developed, the absolute level of hyperkalemia, and the evidence of cardiotoxicity. 

  • diuretics (furosemide i.v.)
  • correcting the source of potassium intake
  • i.v. calcium to enhance cardiac toxicity
  • insulin i.v. + glucose infusion
  • sodium bicarbonate
  • beta-mimetics inh. (albuterol)
  • emergency dialysis 

  References 

  1. Eleanor Lederer, Zygimantas C Alsauskas, Lina Mackelaite, Vibha Nayak, Vecihi Batuman. Hyperkalemia: Practice Essentials, Background, Pathophysiology. Diseases & Conditions - Medscape Reference [online]. https://emedicine.medscape.com/article/240903-overview
  2. Levis JT. ECG diagnosis: hyperkalemia. Perm J. 2013;17(1):69. doi:10.7812/TPP/12-088
  3. https://www.healio.com/cardiology/learn-the-heart/ecg-review/ecg-topic-reviews-and-criteria/hyperkalemia-review
  4. https://rebelem.com/ecg-changes-hyperkalemia/
  5. https://litfl.com/hyperkalaemia-ecg-library/