Synonym
Tubes
- Red or tiger top tube - CO2 content is measured along with electrolytes
- Green top tube or heparinized syringe - test is performed alone or with blood gas analysis
- 5 mL of venous blood
Additional information:
- Fill the tube to its full capacity
- Tighten the cap to prevent exposure to air
- Send the sample immediately to lab on ice
Info
- This test measures bicarbonate ion [HCO3-] levels in the blood and is a part of a basic metabolic panel (BMP)
- Bicarbonate acts as a buffer ion to prevent accumulation of acids in the blood
- Bicarbonate is regulated by the kidneys which can either generate bicarbonate (increasing the bicarbonate level), or fail to reabsorb bicarbonate (decreasing the bicarbonate level)
Clinical
Bicarbonate levels are clinically useful to:
- To detect, evaluate, and monitor electrolyte imbalances in the body due to
- Endocrine disease
- Evaluation of acidosis or alkalosis
- Renal disease
- Lung disorders
- Metabolic disorders
- Sepsis
- To evaluate and monitor acid-base balance in the body due to
- Decreased venous CO2
- Metabolic acidosis
- In compensation to respiratory alkalosis
- Increased venous CO2
- Metabolic alkalosis
- In compensation to respiratory acidosis
Additional information:
- Often measured along with the test for arterial blood gases (ABG)
- Bicarbonate levels are increased in metabolic alkalosis and compensated respiratory acidosis. They are decreased in metabolic acidosis and compensated respiratory alkalosis
- In normal individuals there is a 30% day to day variation
- It is highest in spring and lowest in summer
- In women, it is lowest during the menstrual periods
Nl Result
Consult your laboratory for their normal ranges as these may vary somewhat from the ones listed below.
| Conv. units
(mEq/L) | SI units
(mmol/L) |
|---|
| Adult: | 22-30 | 22-30 |
| Child/Infant: | 20-28 | 20-28 |
| Critcal Values | | <15 |
| | >40 |
Erroneous results may result from:
- A delay in analysis (Lowers bicarbonate concentration)
- Exposure to air (Reduces CO2 levels)
- Specimen not maintained at low temperature (Glycolysis & production of lactic acid will result in a fall in pH & rise in PCO2)
High Result
Conditions associated with elevated bicarbonate levels include:
- GI loss of acids
- NG suctioning
- Vomiting (Severe)
- Respiratory disorders
- Airway obstruction
- Asthma (w/ Resp. Acidosis)
- COPD (w/ Resp. Acidosis)
- Hypoventilation/Respiratory center depression
- Pneumonia or other pulmonary infections
- Acute intermittent Porphyria
- Aldosteronism (Primary)
- Brain tumor
- Conn's syndrome
- Cushing's syndrome
- Metabolic alkalosis
- Respiratory acidosis
- Cardiac disorders
- Hypothyroidism
- Myopathy
- Poliomyelitis
- Drugs
- Acetylsalicylic acid
- Aldosterone
- Amphotericin B
- Anesthetics
- Antacids
- Bicarbonate
- Calcium carbonate
- Carbenicillin
- Carbenoxolone
- Corticosteroids
- Dexamethasone
- Diuretics (Loop)
- Glycyrrhiza
- Laxatives (chronic abuse)
- Mafenide
- Metolazone
- Opiates/Sedatives
- Volume depleting agents
- X-ray contrast agents
Low Result
Conditions associated with decreased bicarbonate levels include:
- Anxiety (due to compensation for respiratory alkalosis with hyperventilation)
- Burns
- Dehydration
- Diabetic ketoacidosis
- Diarrhea (Severe)
- Fever (High)
- Hyperthyroidism
- Metabolic acidosis
- Renal failure
- Respiratory alkalosis (Compensation for)
- Shock
- Starvation (Ketosis)
- Drugs
- 2,4-dinitrophenol intoxication
- Acetazolamide
- Aldosterone antagonists
- Amiloride
- Ammonium chloride
- Aspirin/Salicylate ingestion
- Capreomycin
- Citrates
- Dimercaprol
- Dimethadione
- Diuretics (Thiazides)
- Ether
- Ethylene glycol
- Fluorides
- Gentamicin
- Heroin withdrawal
- Metformin
- Methicillin
- Methyl alcohol
- Nitrofurantoin
- Paraldehyde
- Streptomycin
- Tetracycline
- Triamterene
- Xylitol
References
- A-Z Health Guide from WebMD®: Medical Tests. Bicarbonate. [Homepage on the Internet] ©1995-2006. Last updated July 16, 2004. Last accessed October 28, 2006. Available at URL: http://www.webmd.com/hw/lab_tests/hw3427.asp
- Fuchs S et al. Drug Points: Metabolic abnormality induced by streptomycin. BMJ 1994; 309: 512
- Khanna A et al. Metabolic alkalosis. J Nephrol. 2006 Mar-Apr;19 Suppl 9:S86-96.
- Lab Tests Online®. CO2: The Test. [Homepage on the Internet] ©2001-2006.Last reviewed on April 22, 2005. Last accessed on October 28, 2006. Available at URL: http://www.labtestsonline.org/understanding/analytes/co2/test.html
- Nagler J et al.End-tidal carbon dioxide as a measure of acidosis among children with gastroenteritis. Pediatrics. 2006 Jul; 118(1): 260-7