Hyperkalemia laboratory findings

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Priyamvada Singh, M.B.B.S. [2] ; Aditya Ganti M.B.B.S. [3]

Overview

In a patient who does not have a risk for hyperkalemia, repeating the blood test is indicated before taking any actions unless changes are present on electrocardiography.

Laboratory Findings

Hyperkalemia is defined as serum potassium greater than 5.0-5.5 mEq/L in adults. Levels higher than 7 mEq/L can lead to significant hemodynamic and neurologic consequences, whereas levels exceeding 8.5 mEq/L can cause respiratory paralysis or cardiac arrest and can quickly be fatal. In a patient who does not have a risk for hyperkalemia, repeating the blood test is indicated before taking any actions unless changes are present on electrocardiography.

Grade	Potassium level
Mild	5-7mEq/L
Moderate	7-8.5mEq/L
Severe	>8.5mEq/L

• The first step in diagnosing hyperkalemia is to exclude pseudohyperkalemia by repeating the blood test.

Initial tests

• Complete blood count (CBC)
• Metabolic profile
• Urine potassium, sodium, and osmolality
• Aldosterone

Hyperkalemia

Exclude psuedohyperkalemia by repeating the blood test

Acute rise in potassium

Persistent hyperkalemia

Increase release of K+ from cells Trauma,radiation therapy, DKA, metabolic acidosis

Decreased urinary excreation of K+ rule out aldosterone deficency 24 hr urine K+ excreation

Cause specific

• Blood glucose In patients with history of diabetes mellitus
• Digoxin level
• Arterial or venous blood gas (acidosis)
• Urinalysis (renal insufficiency)
• Serum cortisol and aldosterone levels (mineralocorticoid deficiency)
• Serum uric acid and phosphorus assays (tumor lysis syndrome)
• Serum creatinine phosphokinase (CPK) and calcium measurements and urine myoglobin test (crush injury or rhabdomyolysis)

Psudeohyperkalemia

• Defined as the release of potassium from cells after their breakdown. Most commonly seen during blood collection, so it's required to repeat blood test in patients with a transient rise in potassium without any risk factors.
• Other causes include
  • Clotting increases release of potassium from platelets
  • In patients with history of leukamia where the WBC count is >120,000/microL the potassium is raised to cell fragility
  • Hereditary (familial) forms of pseudohyperkalemia