Potassium, the principal ion inside cells, maintains acid-base balance. Other functions include nerve impulse transmission and contraction of muscles, including cardiac, or heart muscles. Your blood potassium normally ranges from 3.6 to 5.0 milliequivalents per liter.
Hyperkalemia, a common and a potentially life-threatening electrolyte disorder in hospitalized patients, occurs in 1 to 10 percent of patients. Kidney failure commonly causes high levels of potassium. Type 1 diabetes, Addison's disease or adrenal insufficiency, and destruction of red blood cells due to severe injury or burns can also cause high potassium, according to Mayo Clinic. Hyperkalemia most dramatically affects the heart by slowing electrical conduction.
Mild Hyperkalemia: Potassium greater than 6.0, but less than 7.0 mEq/L
Progressive electrocardiogram changes occur with increasing serum potassium levels and require immediate treatment. ECG changes with mild hyperkalemia greater than 6.0, but less than 7.0 mEq/L include increased amplitude and peaking of the "T" waves. Even though lab tests are the gold standard for checking serum electrolytes, commonly a delay of one or more hours occurs before the result is known. Consequently, the electrocardiogram is a useful tool in diagnosing a patient with suspected hyperkalemia.
Moderate hyperkalemia: Potassium greater than, or equal to 7.0 mEq/L, but less than 8.0 mEq/L
A blood potassium level higher than 7.0 mEq/L requires immediate treatment. Patients with hyperkalemia become dull and lethargic, and gradually become confused, according to "Davidson's Principles and Practice of Medicine." ECG changes with moderate hyperkalemia include prolongation of the PR interval.
Severe hyperkalemia: Potassium greater than or equal to 8.0 meq/L
A severely high potassium level, greater than, or equal to 8.0 meq/L, is clinically important due to the danger of cardiac arrest, according to "Davidson's Principles and Practice of Medicine." The patient might experience profound weakness. The electrocardiogram might show absent "P" waves with widening of the QRS complex and merging with the "T" wave, producing a sine wave pattern. Absent P waves mean atrial activity is lost and ventricular arrhythmias, or cardiac arrest, might occur.
Factitious Serum Potassium
It is important to note that high serum potassium might be falsely elevated, or factitious, due to a traumatic blood draw, or a hemolyzed sample, because potassium will be released from red blood cells in both cases. The physician should use good clinical judgment and not react to treat factitious hyperkalemia because hypokalemia might result.
References
- "Harrison's Principles of Internal Medicine"; Dennis Kasper; 2005
- "Davidson's Principles and Practice of Medicine"; John Macleod; 1977
- Mayo Clinic: Hyperkalemia
- Rx MED: Potassium Salts
- ICU room Pearls
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