A green-top tube is used for Arterial Blood Gas (ABG) tests. Specifically, either a sodium heparin or lithium heparin green top tube is used. These tubes contain an anticoagulant, preventing the blood from clotting and therefore giving a sample that can be accurately analysed.
Understanding ABG Tubes
- Green-Top Tubes: These tubes are easily identifiable by their green stopper. They contain either sodium heparin or lithium heparin.
- Anticoagulant: Heparin is an anticoagulant that prevents the blood from clotting, which is crucial for accurate ABG analysis. This is essential because clotted blood can interfere with test results.
- Immediate Inversion: After collecting blood in the green-top tube, it is essential to immediately invert the tube several times to thoroughly mix the heparin with the blood. This ensures proper anticoagulation and prevents clot formation within the tube.
How Heparin Works in ABG Collection
Heparin prevents coagulation by inhibiting the action of thrombin, a key enzyme in the clotting cascade. This action ensures that the blood sample remains in a liquid state suitable for analysis. The type of heparin, whether sodium or lithium, usually doesn’t significantly impact the results, but different laboratories might have preferences.
Practical Insight
The proper collection, immediate inversion, and handling of the sample in a heparinized tube are crucial for accurate and reliable ABG results, which is a critical test for assessing respiratory and metabolic function.
