Quick Review Cards for Medical Laboratory Science

Major Electrolytes Clinical Chemistry Review 93

ANALYTE REFERENCE RANGE CLINICAL SIGNIFICANCE OTHER

Sodium
(Na+)

Potassium
(K+)

136–145 mmol/L

3.5–5.1 mmol/L

↑(hypernatremia): Due to ↑intake or

IV administration, hyperaldosteronism,

excessive sweating, burns, diabetes insipidus.

Causes tremors, irritability, confusion, coma.

↓(hyponatremia): Due to renal or extrarenal

loss (vomiting, diarrhea, sweating, burns) or

↑extracellular fluid volume. Causes weak-

ness, nausea, altered mental status.

↑(hyperkalemia): Due to ↑intake,

↓excretion, crush injuries, metabolic acido-

sis. Can cause muscle weakness, confusion,

cardiac arrhythmia, cardiac arrest.

↓(hypokalemia): Due to ↑GI or urinary loss,

use of diuretics, metabolic alkalosis. Can

cause muscle weakness, paralysis, breathing

problems, cardiac arrhythmia, death.

Major extracellular cation. Contributes almost

half to plasma osmolality. Maintains normal

distribution of water & osmotic pressure. Levels

regulated by aldosterone. Ion-selective electrode

(ISE) is most common method. Normal

Na+/K+ratio in serum approximately 30:1.

Major intracellular cation. Artifactual ↑due to

squeezing site of capillary puncture, prolonged

tourniquet, pumping fist during venipuncture,

contamination with IV fluid, hemolysis,

prolonged contact with RBCs, leukocytosis,

thrombocytosis. Serum values 0.1–0.2 mmol/L

higher than plasma due to release from

platelets during clotting. Most common

method is ISE with valinomycin membrane.

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