Venous Blood Gas Analysis Test
Venous Blood Gas Analysis Test
Blood gas analysis (BGA) is a laboratory test routinely used to assess the acid-base status apart from oxygenation and ventilation in patients who are critically and acutely ill. Arterial blood is collected anaerobically from an artery by a needle puncture or indwelling arterial catheter. The arterial puncture is more painful, hazardous, and technically demanding than venipuncture. By contrast, venipuncture is safe, and easy and requires minimal training. However, in intensive care settings, the patients who require frequent blood gas monitoring have a central venous catheter that helps in a safe and easy sampling of venous blood for laboratory testing.
What is a Venous Blood Gas Analysis test used for?
Venous blood gas analysis is an alternative method to estimate oxygen levels, systemic carbon dioxide, acidity, and pH in the blood that does not need sampling from the artery. This method is particularly convenient in I.C.U., either peripherally or via a central venous catheter from which the blood can be easily and quickly obtained.
The test measures:
1. pH
2. pCO2
3. pO2
4. Bicarbonates
5. Base excess
The pO2 and pCO2 values vary significantly between arterial and venous samples.
It also measures:
1. Electrolytes (sodium, potassium, calcium, chloride)
2. Glucose
3. Urea
4. Lactate
These values are generally similar between arterial and venous samples.
Who should get tested?
This test is done for diagnosing and monitoring patients with different health conditions like breathing disorders, acid-base imbalance, and kidney diseases with the following conditions
Rapid breathing & shortness of breath
Shock
Heart failure
Hemorrhage
Stroke
Uncontrolled diabetes
Chemical poisoning
Drug overdose
Preparation for test
Measurement of blood gas analysis needs obtaining a blood sample from a vein. This process is mostly done in a hospital. Before taking the test, talk to your doctor if you use oxygen therapy or blood thinners.
Interpretation of the test results
The lab report is compared to the normal values given below :
|
|
Arterial blood |
Venous blood |
|
pH |
7.4 (7.35-7.45) |
7.36 (7.33-7.43) |
|
pO2 |
80-100 mm of Hg |
35-40 mm of Hg |
|
pCO2 |
35-45 mm of Hg |
41-51 mm of Hg |
|
Bicarbonate |
22-26 mEq/L |
24-28 mEq/L |
|
O2 saturation |
>=95% |
70-75% |
|
Base excess |
-2 to +2 |
0 to +4 |
FAQs
What are the advantages of venous blood gas analysis over arterial blood gas analysis?
The advantage of venous blood gas analysis is that sample collection is technically easier for venous blood than arterial blood. It causes less pain and discomfort to the patient.
Can venous blood gas analysis be used interchangeably with arterial blood gas analysis?
Venous blood gas analysis provides valuable information about the acid-base balance and oxygenation status, but it is not a substitute for arterial blood gas analysis in all situations.
Arterial blood gas analysis remains the gold standard in accessing the acid-base balance and ventilation status, especially in critically ill patients.
Are there any risks associated with venous blood gas analysis?
Venous blood gas analysis is a relatively safe procedure. However, there is a risk of bruising, bleeding, or infection at the venipuncture site.
When is venous blood gas analysis performed?
Venous blood gas analysis helps to assess acid-base balance, oxygenation, and metabolic status.
Is fasting required for venous blood gas analysis?
Fasting is typically not required for venous blood gas analysis.
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