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ECG Changes of Hyperkalemia

Posted by Marco Torres on

Hyperkalemia is an electrolyte abnormality seen in the emergency department as well as in hospitalized patients and it can be associated with adverse clinical outcomes and death if not treated appropriately. It is important to remember that the electrophysiologic effects of hyperkalemia are directly proportional to both the absolute plasma potassium and its rate of rise. However, neither the ECG nor the plasma potassium alone are an adequate index of the severity of hyperkalemia, and therefore providers should have a low threshold to initiate therapy. Classic teaching of the chronological ECG changes of hyperkalemia include:

  1. Peaked T waves
  2. Prolongation of PR interval
  3. Widening QRS Complex
  4. Loss of P wave
  5. “Sine Wave”
  6. Asystole

Where did the evidence for order of ECG changes of hyperkalemia come from?

The order of ECG changes of hyperkalemia have been defined in the experimental setting, but no uniform order has been documented in animal models [1]. The relationship between serum potassium and cardiac manifestations is even less clear in the clinical setting [2].

How good are ECGs at predicting hyperkalemia? [3]

  • 87 patients admitted from the ED with hyperkalemia
  • ECG read by 2 EM physicians blinded to potassium level
  • Sensitivity: 34 – 43%
  • Specificity: 85 – 86%
  • When only patients with potassium > 6.5 mmol/L were analyzed: Sensitivity 55 – 62%
  • Conclusion: Based on this study the ECG has a poor correlation with detection of hyperkalemia

Any studies looking at the frequency of ECG changes with hyperkalemia? [4]

What is the treatment regimen for hyperkalemia? [5]

Additional Treatment Pearls:

  1. 1 g Calcium Chloride (CaCl) = 3 g Calcium Gluconate: Bryan Hayes (@PharmERToxGuy) had a great post on Academic Life in EM on myths associated with different calcium regimens.
  2. Hypertonic (3%) Saline: Should be restricted to patients with hyponatremia and concurrent hyperkalemia. Its effects have not been established in eunatremic patients.
  3. Insulin: 10 Units of regular insulin + dextrose (25 g as 50% solution) lowers plasma potassium by about 0.6 mmol/L. Be careful as a single bolus of 25 g of dextrose has been shown to be inadequate ion prevention of hypoglycemia at 60 minutes.
  4. Beta Agonists: 10 mg and 20 mg of inhaled albuterol decreased serum potassium by 0.6 mmol/L and 1 mmol/L, respectively. Mild tachycardia is most common side effect.
  5. Bicarbonate: Bolus injection of sodium bicarbonate has not been studied. The dogma of bolus bicarbonate was derived from studies using a prolonged (4 – 6 hr) infusion of bicarbonate which does not reduce plasma potassium in patients with dialysis-dependent renal failure. Infusion sodium bicarbonate over 4 – 6 hours may have some benefit in excretion of serum potassium in the setting of metabolic acidosis.
  6. Exchange Resin: The onset of action is very long (2 hours to onset, and 6 ours to maximum effect) and there have been case reports of patients developing colonic necrosis. Also there have been studies that show no statistical benefit at 4, 8, and 12 hours [6].
  7. Hemodialysis: Definitive treatment of hyperkalemia. Watch out for rebound hyperkalemia which can occur in 30% of patients an hour after dialysis.

Clinical Bottom Line: Neither the ECG nor the plasma potassium alone are an adequate index of the severity of hyperkalemia, and providers should have a low threshold to initiate cardiac membrane stabilization in the setting of hyperkalemia and no ECG changes.

References:

  1. Ettinger PO et al. Hyperkalemia, Cardiac Conduction, and the Electrocardiogram: A Review. Am Heart J 1974. PMID: 4604546
  2. Acker CG et al. Hyperkalemia in Hospitalized Patients: Causes, Adequacy of Treatment, and Results of an Attempt to Improve Physician Compliance with Published Therapy Guidelines. Arch Intern Med 1998. PMID: 9570179
  3. Wrenn KD et al. The Ability of Physicians to Predict Hyperkalemia from the ECG. Ann Emerg Med 1991. PMID: 1952310
  4. Montague BT et al. Retrospective Review of the Frequency of EC Changes in Hyperkalemia. clinical J Am Soc Nephrol 2008. PMID: 18235147
  5. Weisberg LS. Management of Sever Hyperkalemia. Crit Care Med 2008. PMID: 18936701
  6. Gruy-Kapral C et al. Effect of Single Dose Resin-cathartic therapy on Serum Potassium Concentration in Patients with End-Stage Renal Disease. J Am Soc Nephrol 198. PMID: 9773794

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