The Goal of Heparinization in ABG

To coat the syringe with a thin, even layer of heparin (an anticoagulant) to prevent the blood sample from clotting, while avoiding excess heparin that can dilute the sample and distort the results (especially pH, PaCO₂, and electrolytes).

Method 1: Using a Pre-Heparinized Syringe (Standard Practice)

• What it is: A commercially prepared, sterile, disposable syringe pre-treated with a precise amount of lyophilized (dried) lithium heparin.
• Procedure:
  1. Remove from packaging.
  2. Gently push the plunger in and pull it back a few times to distribute the dried heparin coating evenly on the barrel walls.
  3. Expel ALL excess air and heparin crystals by holding the syringe upright, tapping it, and pushing the plunger to the “dead space” volume (usually to the 1 mL mark on a 3 mL syringe). A small pellet of dried heparin may be expelled.
  4. The syringe is now ready. Do not pull or push the plunger again until the needle is in the artery, as this will draw in air.

Method 2: Manual Heparinization (For Plain Syringes – Less Common)

This requires sterile technique and is prone to error. Not recommended for routine clinical use.
Materials Needed: Sodium or lithium heparin solution (typically 1000 IU/mL), a plain syringe and needle, a sterile container.

Step-by-Step:

1. Aspirate Heparin: Draw up a small amount of heparin solution (about 0.5-1 mL) into the syringe.
2. Coat the Syringe: Hold the syringe horizontally, roll and tilt it to coat the entire interior surface, including the hub and the base of the plunger.
3. Expel ALL Excess: Point the syringe upright and forcefully expel ALL the liquid heparin. A thin, barely visible film should remain. Only the heparin coating the walls is needed.
4. Check for Dead Space: The heparin solution will fill the needle and hub (“dead space”). This tiny volume is acceptable and will mix with the blood sample.