Providence Nursing Institute Clinical Academy Perinatal Curriculum Last reviewed: June 13, 2016 Providence Clinical Academy 2016.06

Intro to Acid-Base Status Interpreting FHR and Cord Gases “What does it mean?” Providence Clinical Academy 2016.06

Reduced gas exchange occurs at approximately 20 mmHg Providence Clinical Academy 2016.06

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! Providence Clinical Academy 2016.06

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) Providence Clinical Academy 2016.06

Aerobic Primary mode of energy production in a well-oxygenated fetus Fetal Metabolism Aerobic L. Miller, Advanced Fetal Monitoring Course (2015) Providence Clinical Academy 2016.06

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) Providence Clinical Academy 2016.06

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. Providence Clinical Academy 2016.06

Cord Gas Interpretation #1 pH #2 Base Deficit #3 pCO2 Read cord gas results in this order Providence Clinical Academy 2016.06

2016.06 Providence Clinical Academy L. Miller, Advanced Fetal Monitoring Course (2015) 2016.06

Cord Gas Interpretation pH 7.01 pO2 9 pCO2 78 HCO3 12 BD 17 Cord Gas Interpretation Practice #1 Respiratory Metabolic Mixed Providence Clinical Academy 2016.06

Cord Gas Interpretation pH 7.10 pO2 20 pCO2 62 HCO3 21 BD 7 Cord Gas Interpretation Practice #2 Respiratory Metabolic Mixed Providence Clinical Academy 2016.06

Cord Gas Interpretation pH 6.96 pO2 12 pCO2 58 HCO3 21 BD 17 Cord Gas Interpretation Practice #3 Respiratory Metabolic Mixed Providence Clinical Academy 2016.06