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ELECTROLYTES, SERUM (OR HEPARINIZED PLASMA): SODIUM, POTASSIUM, CHLORIDE, CARBON DIOXIDE

Item Value
Available Stat? Yes
Test code Na, K, Cl, CO2
Performed by? Chemistry
Sendout? no
Price range $$
In House Availability Routine: 7 days.
STAT: 24 hours/7 days.
Moderately hemolyzed serum will not be assayed for potassium
Principle 1. Sodium: potentiometric procedure by use of a sodium ion-selective glass electrode.

2. Potassium: potentiometric procedure by means of a potassium ion-selective electrode.

3. Chloride: potentiometric procedure by means of chloride ion-selective electrodes.

4. Carbon Dioxide: Enzymatic end-point.
Interpretation 1. Sodium: decreased with excessive sweating, diarrhea, pyloric obstruction, malabsorption, adrenal cortical insufficiency, diabetic acidosis, diuretics, renal tubular acidosis, and renal failure; increased with dehydration, primary aldosteronism.

2. Potassium: decreased with diarrhea, pyloric obstruction, starvation, malabsorption, primary aldosteronism, diuretics; Increased with adrenal cortical insufficiency, acute renal failure and hemolysis.

3. Chloride: decreased with pulmonary emphysema, congestive heart failure, sweating, diarrhea, pyloric obstruction, primary aldosteronism, adrenal cortical insufficiency, diabetic acidosis, thiazide, mercurial diuretics; increased with dehydration, salicylates.

4. Carbon Dioxide: decreased with diarrhea, salicylates, diabetic acidosis, diuretics, and in renal failure; increased with emphysema, pyloric obstruction, and in primary aldosteronism.
Container type gel tube (gold or green top)
Amount to Collect 2 mL
Sample type Blood
Special instructions Since electrolyte components undergo changes upon prolonged contact with RBCs, it is necessary to separate the serum from the clot without delay (see Interferences). There may be some postprandial depression of serum potassium. Moderately hemolyzed serum will not be assayed for potassium. Do not draw from an arm receiving an IV transfusion.
Normal range
Sodium (age) 0-2 wks 2 wks-2 yrs 2-16 yrs 16-90 yrs >90 yrs
mmol/L 133-146 139-146 138-145 136-145 132-146


Potassium (age) 0-2 wks 2 wks-1 yr 1-16 yrs >16 yrs
mmol/L 3.7-5.9 4.1-5.3 3.4-4.7 3.5-5.1


Chloride (age) 0-30 days >30 days >90 yrs
mmol/L 98-113 98-109 98-111


CO2 (age) 0-2 wks 2 wks-16 yrs >16 yrs
mmol/L 13-22 20-28 22-29


Anion Gap (age > 16 yrs) 7-16



Calculation of Anion Gap: Na – (Cl + CO2). Prior to 7/1/04,
Gap calculation included K (Potassium).

The following values are considered Critical Values and are called to the
physician or patient care unit immediately.


Critical Values: Low High
Sodium < 125 > 155
Potassium < 3.0 > 6.0
Chloride -- --
Carbon Dioxide < 15 > 40

Synonyms Carbon Dioxide;Chloride, Serum;Metabolic Basic Panel (METB): NA, K, CL, CO2, CREA, BUN, GLUC, CA;Metabolic Comprehensive Panel (METC): METB, TBIL, TP, ALB, ALT, AST, ALKP);Potasium;Sodium, Serum;
Stability Serum Sodium, Potassium, and Chloride are stable at refrigerator or room temperature for at least 2 weeks. Stable indefinitely when frozen. However, Carbon Dioxide cannot be adequately preserved and loss of CO 2should be expected by storage of more than 2 hours at room temperature.
Interferences Hemolysis of RBC will raise the K+, as will clotting with platelet aggregation and damage to leukocytes. Therefore, it is essential to separate serum from clot immediately.
References 1. Bayer(TM) Clinical Methods ISE Module B01-4171-51; B01-4173-51 Advia 1650 Operator's Guide. PN 073-5001-09. Last accessed June 2003. Siemens Medical Solutions Diagnostics, Malvern, PA.

2. Bayer(TM) Clinical Methods CO2 (45) B01-4146-01 Advia 1650 Operator's Guide. PN 073-5001-09. Last accessed June 2003. Siemens Medical Solutions Diagnostics, Malvern, PA.

3. Eisenman, G.: Glass electrodes for hydrogen and other cations; Principles and practice. NY, Marcel Dekker Inc., 1967:2.

4. Pioda, L.A.R., Siman, W., Bosshard, H.R., Curtius, H.C.: Determination of potassium ion concentration in serum using a highly selective liquid-membrane electrode. Clin Chem Acta, 29:289-293, 1970.

5. Young, DS. Effects of Drugs on Clinical Laboratory Tests, 5th ed. Washington D.C.: AACC Press; 2000.
CPT coding 84132, 82435 , 82374
Last Updated 10/26/2012 9:58:52 AM
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