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What do Cord Gas values mean?

Posted Jun 16 2008 10:51pm

In the different hospitals I have worked at over the years where the respiratory therapists either draw or run the umbilical cord gases I have often wondered about what the normal values of a cord gas was. Just from running a lot of cord gases I have came to my own conclusion of what a cord gas value should probably be but have never really looked into what the real normal values are and what a value out of the norm would mean.

I have done some research online to see what I could find out. Here are some fact about umbilical cord gases and the normal values:


  • The umbilical cord blood is studied for the status of the fetal acid base. Cord gases are obtained to detect the presence or absence of acidosis and to decide whether the cause of the acidosis is respiratory or metabolic. Establishing the source and type of acidosis make it easier to a.) plan resuscitation b.) treat complications.
  • Umbilical cord blood pH and acid-base balance is most useful in association with the delivery of an infant with a low APGAR score.
  • Only newborns who have a persistent APGAR score of 0-3 for 5 minutes or longer and an umbilical artery blood pH of less than 7.00 are at risk of manifesting anoxic brain injuries.
  • Premature infants are at higher risk for intracranial hemorrhage and subsequent neurological dysfunction, such as cerebral palsy. Without umbilical cord blood gas analysis, these neurological complications could be incorrectly attributed to intrapartum or birth asphyxia, especially if the latter is solely based on APGAR scores. Normal umbilical cord blood values in the premature infant virtually eliminate the diagnosis of significant intrapartum hypoxia or birth asphyxia.

The information I used above was found from different sources who are all basically saying the same thing. Now how about those normal values and the values the show a respiratory or metabolic acidosis.

As a reminder the umbilical cord is backwards as the Venous side carries the oxygenated blood and the Arterial side the unoxygenated blood. Doctors prefer to use the Venous cord blood but can assess PH with he arterial side also. Also these values are not set in stone, they are just a reference point, I have came across values the differ but very slightly.


After Birth­Normal Fetal cord blood pH and gas values:




VEIN

ARTERY

pH

7.25 - ­7.35 7.28

p02

28­ - 32 mmHg. 16­ - 20 mmHg.

pC02

40­ - 50 mmHg. 40 - ­50 mmHg.

Base Excess

+/- 0 - ­5 mEq/Liter +/- 0­ - 10 mEq/Liter

Abnormal Venous cord blood pH and gas values

Respiratory Acidosis

Metabolic Acidosis

pH

<>< 7.25

P02

Variable < 20 mmHg

pC02

> 50 mmHg 45­ - 55 mmHg.

Base Deficit

< 10mEq/liter
> 10mEq/liter





Respiratory Acidosis

Metabolic Acidosis


Low pH Low pH

High pC02 Normal to high pC02

Normal Base Excess High base excess



As always I hope you have learned or been refreshed on this topic, I know just researching for this information I have learned a bit of information.

Thanks for reading.

Drive on RT's
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