Blood gases, venous-201
Test info
- pH
- PCO2
- PO2
- HCO3
- Base excess
- O2 saturation
Blood gas testing is used to evaluate respiratory diseases, conditions that affect the lungs, determine the effectiveness of oxygen therapy, and provide information about the body's acid / base balance, which can reveal important clues about lung and kidney function and the body's general metabolic state.
Specimen
Blood gas syringe
Warning: Should be collected at a hospital site
Must arrive in lab within 30 minutes.
Expel all air from the sample
Blood gas syringe
- Immediately after collection, mix tube thoroughly by gentle inversion, 8 - 10 times, to prevent clotting
- The tube should be fully filled, unopened, and must arrive at AHL Central lab within one (1) hour of collection.
Do not spin and do not open
Dk green Sodium heparin (Na hep), no gel
Time sensitive
Refrigerated - 30 minutes
- Vacutainer collection tubes submitted for venous blood gas analysis cannot be sent through the Pneumatic tube system (PTS)
- Clotted specimens
- Insufficient quantity
- Incorrect anticoagulant (anything other than lithium heparin) or contaminated
- Specimens that do not meet transportation and storage requirements
- Specimen that has been exposed to air or contains air bubbles
- Specimen received in a plasma separator (PST) tube
- Improper labels (unlabeled or mislabeled)
- Leaking container resulting in compromised specimen
- Quantity not sufficient (QNS)
Performance
Ion selective electrodes
Clinical and Interpretive info
|
Venous blood gas reference ranges |
|
|
Component |
Reference range |
|
pH, venous |
7.32-7.43 |
|
pCO2, venous |
41-51 mmHg |
|
pO2, venous |
34-50 mmHg (0-<1 day) |
|
34-40 mmHg (1 day - >1 mo) |
|
|
35-40 mmHg (≥1 mo) |
|
|
HCO3, venous |
22-29 mmol/L |
|
Base excess |
-2.0 - 3.0 |
|
O2 saturation, venous |
40.0-70.0 % (<1 day) |
|
70-75 % (≥1 day) |
|
Blood gasmeasurements determine the acidity (pH) of the blood, and how much oxygen and carbon dioxide the blood contains. The pH of the blood depends on the relationship of the components of the bicarbonate buffer system – bicarbonate and carbonic acid. Carbonic acid is proportional to the dissolved carbon in the blood (0.03 × pCO2).
The plasma bicarbonate concentration is controlled mainly by the kidneys and is affected by the end products of metabolism of cells. It is referred to as the metabolic component. pCO2 is controlled by the rate of excretion of CO2 by the lungs. It is referred to as the respiratory component.
A low pH (acidosis) may be due to a fall in the HCO3- (metabolic acidosis) or a rise in pCO2 (respiratory acidosis). The body responds to a change in one component by producing a similar change in the other. This is called compensation, and is usually incomplete.