A test that measures oxygen, carbon dioxide, and acid-base balance in the blood. It is used in the diagnosis of respiratory and metabolic disorders.
Indication
- Suspected respiratory failure (COPD exacerbation, asthma attack, pneumonia)
- Metabolic acidosis or alkalosis (diabetic ketoacidosis, kidney failure)
- Evaluation of sepsis and shock
- Monitoring of patients on mechanical ventilation
- Suspected poisoning (carbon monoxide, salicylate)
- Acid-base monitoring of intensive care patients
- Pre-operative assessment of respiratory reserve
Preparation
- No special preparation is generally needed
- In patients receiving oxygen therapy, the oxygen level at the time of sampling is recorded
- Body temperature is noted before the procedure (for interpreting results)
How it's performed
- A doctor or nurse draws blood from the wrist (radial), groin (femoral), or arm artery
- When a venous sample is requested, blood is drawn from a vein in the arm
- The sample is collected into a sealed tube without air contact and quickly delivered to the laboratory
- The analyzer measures pH, pCO2, pO2, bicarbonate (HCO3), and base deficit values
- Results are usually available within 10-15 minutes
Post-procedure
- Pressure is applied to the puncture site for 5-10 minutes (due to bleeding risk in arteries)
- The area is observed for hematoma (blood collection)
- In critically ill patients, the test may be repeated based on response to treatment
- Results are interpreted together with the clinical picture and other tests
Risks
- Mild pain or bruising at the needle insertion site
- Hematoma (especially with arterial sampling)
- Rare vascular spasm or transient circulatory disturbance
- Very rarely, infection
FAQ
Is drawing blood from an artery painful?
It can be more uncomfortable than a venous sample. A brief stinging and throbbing sensation may be felt at the wrist.
What is the normal pH value?
In arterial blood, pH ranges from 7.35 to 7.45. Below this range is considered acidosis and above it alkalosis.
How long does it take to get the result?
Modern analyzers provide results in 10-15 minutes. For this reason, the test is frequently used in emergency departments and intensive care units.
Is fasting required?
Fasting is generally not required. However, your physician may give different instructions in special situations.
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