Hyperkalemia
Kent D.W. Bream and Judith A. Fisher
Hyperkalemia is probably the most serious electrolyte abnormality. Normal serum potassium is 3.5 to 5.0 mEq/L. Severe hyperkalemia, however, is patient specific and not simply defined by a cut-off of 5.0. A serum potassium (K+) of 6.0, for example, in one patient may lead to a fatal cardiac arrhythmia, whereas it is asymptomatic and without morbidity in another.
Approach
Hyperkalemia is usually not sustained without a disorder of the normal potassium regulatory system. In an otherwise healthy individual, routine screening of potassium is not indicated. Potassium, however, should be monitored in patients on certain medications, or with acid-base disorders, abnormalities in renal function, and disorders of aldosterone secretion. These patients are at risk for potentially fatal hyperkalemia (1–4).
A. Special concerns. In diagnosing hyperkalemia, the most important characteristic to rule out is cardiac electrical abnormality on the electrocardiogram (ECG). Hyperkalemia can remain asymptomatic until its effects on cardiac conduction lead to cardiac arrest. This potential consequence requires that hyperkalemia be diagnosed and treated promptly. ECG changes include flattening of the P wave, widening of the QRS complex, and peaking of the T wave. When the QRS and T waves merge, a sine wave pattern develops which represents the severest form of cardiac abnormality.
Depending on the K+ level, some patients will require emergent evaluation for hyperkalemia. Patients with a K+ greater than 7.0 in any circumstance should have immediate cardiac evaluation. When the potassium is below 7.0, numerous factors determine the urgency of evaluation including the historical cause, the possible duration of hyperkalemia, and the probability that the level will continue to increase without treatment. These three factors, and the absolute value of serum K+, suggest the timing of cardiac evaluation.
B. Causes of hyperkalemia. Four causes of hyperkalemia are seen: spurious causes, redistribution abnormalities, renal disorders, and hormone deficiencies. Spurious hyperkalemia is the most frequent cause of hyperkalemia in a healthy patient. The most common redistribution abnormality is acidosis. Renal causes are most frequently renal insufficiency or failure with a concomitant potassium load. Finally, uncontrolled diabetes is the major cause of hyperkalemia resulting from hormonal causes (Chapter 14.1) (Table 17.5).
References
1. Evers S, Engelien A, Karsch V, Hund M. Secondary hyperkalemic paralysis. J Neurol Neurosurg Psychiatry 1998;64(2):249–252.
2. Halperin ML, Kamel KS. Potassium. Lancet 1998;352(9122):135–140.
3. Martinez-Maldonado M. Approach to the patient with hyperkalemia. In: Kelley WN, ed. Textbook of internal medicine. Philadelphia: Lippincott-Raven, 1997.
4. Wallach J, ed. Interpretation of diagnostic tests, 6th ed. Boston: Little, Brown and Company, 1996.
Pictures
Book Source Details
- Book Title: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter
- Author(s): Robert B. Taylor (editor)
- Year of Publication: 2000
- Copyright Details: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter, Copyright © 2000 Lippincott Williams & Wilkins.
Other Book Chapters Related to Hyperkalemia
Read excerpts from these other book chapters related to Hyperkalemia:
Medical Books Excerpts
- Hyperkalemia
- "The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter" (2000)
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Copyright Details: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter, Copyright © 2008 Williams & Wilkins.
More About Causes of Hyperkalemia
» Next page: Potassium imbalance (Handbook of Diseases)
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