Page 177 - pathology_services_handbook_5th_edition_2018

4.2 Fetal Cord Blood Gas Specimen

A) Specimen Collection

1. Rinse two (2) 1 ml disposable syringes with heparin (5,000 units per ml). Expel
the excess heparin; leaving only the dead space of the syringes filled by the
heparin. INTEGRATED
2. Double clamp the umbilical cord to isolate 10 cm of cord segment immediately
after birth.
3. Wipe the segment of cord to be sampled with alcohol swab.
4. Identify vessels in cord: 2 arteries (small vessels) and 1 vein (large vessel).
5. Insert the needle into an artery between the clamps, and withdraw 1 mL (at
least 0.5 ml) of blood (Always sample the artery first as the vessel is smaller and
the distended vein will stabilize the artery). Follow Procedure A3-A8 as in 4.1
Blood Gas and Lactate Specimen.
6. Repeat Procedure 5 with the vein.

B) Specimen Transportation

1. Follow Procedure B1-B2 as in 4.1 Blood Gas and Lactate Specimen.

Notes:
In the event when only one vessel can be sampled, the umbilical artery should be
sampled.

4.2 Ammonia

Specimen for ammonia analysis requires special procedure to prevent changes in
ammonia concentration while and after the specimen is drawn.

A) Preparation before Specimen Collection

1. The specimen should be collected in a fasted state (or at least 4 - 6 hours after
a meal), not following physical exercise, and smoking should be avoided for at
least 9 hours before specimen collection, unless in an emergency.
2. Contact Integrated Laboratory before the specimen is taken to ensure that
specimen analysis can be performed without delay.

B) Procedure of Collection

1. A venous specimen is best drawn without a tourniquet or immediately after the
tourniquet has been applied briefly.

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