- It is done on serum or plasma of the patient (plasma arterial or venous can be used).
- The best anticoagulant is heparin.
- The test should be done as soon as possible and minimize the time interval between a sample taken and analyzed.
- Collect sample anaerobically and heparin is preferred anticoagulant.
- It assists in evaluating the pH of the patient.
- It also assists to evaluate electrolyte balance.
- Bicarbonate is the most important buffer in the blood which maintains the pH (acid-base balance).
- Bicarbonate is the measure of a metabolic (Kidney) component of acid-base balance.
- Bicarbonate is easily regulated by the kidney which excretes it in excess and retains when needed.
- In the body most of the CO2 is in the form of HCO3, So CO2 level in blood is the measure of HCO3.
- The CO2 contents measure H2CO3, dissolved CO2, and the bicarbonate ions HCO3 that is present in the blood.
- Bicarbonate level is affected by a variety of respiratory and metabolic disturbances which affect acid-base balance.
- HCO3 ion is a measure of the metabolic kidney part of the acid-base balance.
- HCO3 is exchanged for other ions like Chloride and Phosphate to maintain electroneutrality.
- When HCO3 level increases, the pH also increases.
- Kidneys play important role in the balance of the acid-base system.
- In respiratory acidosis, kidney compensates by increased reabsorption of HCO3.
- In respiratory alkalosis, kidney compensates by increased excretion of HCO3.
- Arterial blood: 21 to 28 meq/L
- Venous blood: 22 to 29 meq/L
- Peritoneal fluid = 24 to 29 meq/L
- Duodenal fluid = 4 to 21 meq/L
- Pancreatic fluid = 66 to 127 meq/L
- For SI unit multiplication factor is 1, that will be in mmol/L
Lower-than-normal levels may be seen in:
- Addison disease
- Ethylene glycol poisoning
- Kidney disease
- Lactic acidosis
- Metabolic acidosis
- diabetic ketoacidosis.
- Methanol poisoning
- Salicylate toxicity (such as aspirin overdose)
- Liver disease
Higher-than-normal levels may be seen in:
- Breathing disorders (compensated respiratory acidosis)
- Cushing syndrome
- Excessive vomiting
- Ingestion of excessive amount of antacid, diuretics and steroids
- Severe vomiting.
The following conditions may also alter bicarbonate levels:
- Renal tubular acidosis, distal.
- Renal tubular acidosis, proximal.
- Respiratory acidosis: There is an absolute CO2 excess that results in decreased pH and increased pCO2 and a base deficit.
- Respiratory alkalosis: There is an absolute CO2 deficit that results in increased pH and decreased pCO2 and a base excess.
- Metabolic acidosis: There is an absolute HCO3 deficit resulting in decreased pH and HCO3.
- Metabolic alkalosis: There is absolute HCO3 excess, resulting in increased pH and HCO3 level.
||22 to 26 meq/L
||35 to 45 mm HG
||7.35 to 7.45
||Prolonged vomiting, nasogastric drainage or NaHCO3 overdoses
||Diabetes, intestinal fistula, and kidney disease
||Drugs causing respiratory depression
Possible References Used
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