Carbon Dioxide, Total

Total carbon dioxide consists of carbon dioxide (CO2) in solution or bound to proteins, bicarbonate (HCO3 ¢ ), carbonate (CO32 ¢ ), and carbonic acid (H2CO3). In practice, 80 " 90% is present as HCO3 ¢ and is a general guide to the bodys buffering capacity. It is usually measured with electrolytes as a panel.

Normal range:

0 " 2 years: 20 " 25 mmol/L

2 " 16 years: 22 " 28 mmol/L

>16 years: 24 " 32 mmol/L

Use

To evaluate the total CO32 ¢ buffering system in the body as well as the acid " base balance

Interpretation

Increased In

Respiratory acidosis with CO2 retention

Metabolic alkalosis (e.g., prolonged vomiting)

Airway obstruction

Alcoholism

Aldosteronism

Cardiac disorders

Emphysema

Fat embolism

Pulmonary dysfunction

Renal disorders

Decreased In

Respiratory alkalosis, as in hyperventilation

Metabolic acidosis (e.g., diabetes with ketoacidosis)

Alcoholic ketosis

Dehydration

Diarrhea

Head trauma

High fever

Hepatic disorders

Hyperventilation

Malabsorption syndromes

Starvation and uremia

Limitations

Antacids, corticotrophin, mercurial and thiazide diuretics, and sodium bicarbonate increase blood levels.