Electrolyte disturbance
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
Synonyms and keywords: abnormal electrolytes, abnormal lytes, lytes
Overview
Electrolytes are electrically charged solutes necessary to maintain body homeostasis. The main electrolytes include Sodium (Na), Potassium (K), Chloride (Cl), Calcium (Ca), Phosphorus (P), and Magnesium (Mg). These electrolytes are involved in multiple physiologic and neurohormonal reactions necessary to maintain neuromuscular, neuronal, myocardial, and acid-base balance. Their balance are mainly regulated by renal and endocrine systems, any changes in their balance may be life threatening. Electrolytes are in balance to achieve neutral electrical charges. Electrolytes could be classified based on their electrical charge to anions and cations. Anions include bicarbonate, chloride, and phosphorus. Cations are calcium, magnesium, potassium, and sodium. Sodium and chloride are the major extracellular ions that has the greatest impact on serum osmolality (solute concentration in 1 liter of water). Calcium and bicarbonate are the other major extracellular electrolytes. Main intracellular electrolytes are potassium, phosphorus, and magnesium.
Nomenclature
There is a standard nomenclature for electrolyte disorders:
- The name starts with a prefix denoting whether the electrolyte is abnormally elevated ("hyper-") or depleted ("hypo-").
- The word stem then gives the name of the electrolyte in Latin. If no Latin equivalent exists, then the corresponding term in English is used.
- The name ends with the suffix "-emia," meaning "in the blood." (Note, this doesn't mean that the disturbance is only in the blood; usually, electrolyte disturbance is systemic. However, since the disturbance is usually detected from blood testing, the convention has developed.)
For instance, elevated potassium in the blood is called "hyperkalemia" from the Latin term for potassium, "kalium".
Causes
- Drug side effect: Hydrochlorothiazide, Pergolide
Table of common electrolyte disturbances
| Electrolyte | Ionic formula | Normal limits (mg/dl) | Elevation disorder | Depletion disorder |
|---|---|---|---|---|
| Sodium | Na+ | 135-145 | hypernatremia | hyponatremia |
| Potassium | K+ | 3.5-5 | hyperkalemia | hypokalemia |
| Calcium | Ca2+ | 8.9-10.1 | hypercalcemia | hypocalcemia |
| Magnesium | Mg2+ | 1.5-2.5 | hypermagnesemia | hypomagnesemia |
| Chloride | Cl- | 96-106 | hyperchloremia | hypochloremia |
| Phosphate | PO43- | 2.5-4.5 | hyperphosphatemia | hypophosphatemia |
| Bicarbonate | HCO3- | 22-28 (mmol/l) | hyperbicarbonatemia | hypobicarbonatemia |
Electrolyte Abnormalities and ECG Changes
The most notable feature of hyperkalemia is the "tent shaped" or "peaked" T wave. Delayed ventricular depolarization leads to a widened QRS complex and the P wave becomes wider and flatter. When hyperkalemia becomes severe, the ECG resembles a sine wave as the P wave disappears from view. In contrast, hypokalemia is associated with flattenting of the T wave and the appearance of a U wave. When untreated, hypokalemia may lead to severe arrhythmias.
The fast ventricular depolarization and repolarization associated with hypercalcemia lead to a characteristic shortening of the QT interval. Hypocalcemia has the opposite effect, lengthening the QT interval.
Differentiating electrolyte disturbances from other diseases
Electrolyte disturbance must be differentiated from other causes of headache, altered mental status and seizures such as brain tumors and delirium trmemns.