Heparin tubes are used in clinical biochemistry.
The tube is coated with the anti-coagulant Sodium-Heparin.
Heparin activates antithrombin, i.e. blocking the coagulation cascade.
The Sodium Heparin in BD Vacutainer tubes is spray dried onto the inner walls to achieve the best possible solubility.
To avoid micro-clotting, mix the Heparin tube with 8-10 inversions immediately after the blood sample has been taken.