1. Providence Nursing Institute Clinical Academy
Perinatal Curriculum
Last reviewed: June 13, 2016
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2. Intro to Acid-Base Status
Interpreting FHR and Cord Gases
“What does it mean?”
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3. Reduced gas exchange occurs at approximately 20 mmHg
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4. Minimum palpable strength
If you can palpate the contraction, then it is having some effect on blood flow and gas exchange
Minimum palpable strength
If you can palpate a contx then it is having some effect on blood flow!
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5. Study from Bakker et al. demonstrates that increased uterine activity (especially decreased relaxation time) is significantly associate with a higher incidence of an umbilical artery pH of ≤ 7.11
Bakker, Kurver, Kuik, & Van Geijn (2007)
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6. Aerobic Primary mode of energy production in a well-oxygenated fetus
Fetal Metabolism
Aerobic
L. Miller, Advanced Fetal Monitoring Course (2015)
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7. Anaerobic Happens when oxygen is not available
Produces much less energy compared to aerobic metabolism
Uses glucose and glycogen stores
Produces lactic acid
Needs a buffer – HCO3 (bicarb)
Fetal Metabolism
Anaerobic
L. Miller, Advanced Fetal Monitoring Course (2015)
L. Miller, Advanced Fetal Monitoring Course (2015)
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8. Fetal Acidemia Problem: Too much CO2 – can’t clear it
Respiratory
Metabolic
Problem: Too much CO2 – can’t clear it
First breath at birth can correct this issue
Problem: Not enough O2
Leads to lactic acid production
Potential for injury
Base deficit (or base excess) reflects the severity
Remember, in normal aerobic metabolism, the end products are energy, CO2 & H2O.
When uterine, placental & cord blood flow are all functioning properly, the by-products
CO2 & H2O are efficiently cleared. If blood flow is decreased, CO2 may not be effectively
removed and will accumulate, quickly turning into hydrogen & bicarbonate ions. The
bicarbonate ions shift into the tissue. The accumulation of free hydrogen ions in the
blood causes a decrease in pH. This results in a respiratory acidemia and is related to
the accumulation of CO2.
Should blood flow decrease resulting in significant hypoxia, the peripheral tissues will
shift into anaerobic metabolism, utilizing glucose as well as any stored glycogen. Lactic
acid is the by-product here and lactic acid must be buffered, or neutralized with a base,
which is bicarbonate (HCO3). When the amount of lactic acid exceeds fetal buffering
capacity, metabolic acidemia is the end result. Should the hypoxia become severe
enough (or prolonged enough), metabolic acidosis may occur not only in the peripheral
tissues, but it may extend to the vital organs (brain, heart, adrenals) where blood flow
was initially redistributed as a protective mechanism. Once metabolic acidosis reaches
these vital organs, the fetus is at risk for organ damage. The severity of metabolic
acidemia is evidenced by the base deficit (reported as a positive number, known as
base excess when reported as a negative number). The greater the base deficit, the
more the fetus has “used up”, or exceeded, its buffering capacity and therefore the more
severe the metabolic acidemia.
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9. Cord Gas Interpretation#1 pH #2
Base Deficit #3
pCO2
Read cord gas results in this order
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10. 2016.06 Providence Clinical Academy
L. Miller, Advanced Fetal Monitoring Course (2015)

11. Cord Gas InterpretationpH
pO2 9
pCO2 78
HCO3 12
BD 17
Cord Gas Interpretation
Practice #1
Respiratory
Metabolic
Mixed
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12. Cord Gas InterpretationpH
pO2 20
pCO2 62
HCO3 21
BD 7
Cord Gas Interpretation
Practice #2
Respiratory
Metabolic
Mixed
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13. Cord Gas InterpretationpH
pO2 12
pCO2 58
HCO3 21
BD 17
Cord Gas Interpretation
Practice #3
Respiratory
Metabolic
Mixed
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