Umbilical Cord Blood Gases | Romanucci & Blandin
When the baby is inside of the mother’s uterus, they are dependent on their mother for exchanging oxygen and carbon dioxide. Although a fetus does develop lungs while in the womb, they do not use their lungs for breathing the same way that they do once they are born. Fetus “breathing” happens in the intervillous space inside of the placenta, which is where the maternal blood travels. The blood that gets oxygenated from the mother is diffused into capillaries inside of the placenta. The umbilical vein inside of the umbilical cord then is able to get this oxygenated blood and brings it to the baby’s heart, which will then pump the blood to the baby’s body. Once the blood has been used by the baby, it is taken away from the heart and brought back to the placenta.
Also in the intervillous space, carbon dioxide is diffused into the mother’s circulation to enable her to get rid of it when she exhales and oxygen is brought into the baby’s circulation. This gas exchange’s main function is to bring in oxygen for breathing and to eliminate carbon dioxide.
The umbilical artery blood may be examined to figure out if a baby suffered oxygen deprivation, which is called an anoxic or hypoxic/ischemic event. If it is found that the umbilical artery blood is academic, that will usually mean that anaerobic metabolism has happened, which is metabolism that happens if oxygen was unavailable. This is typically an indicator that an anoxic event has taken place. Anoxic/hypoxic ischemic events are known to cause hypoxic ischemic encephalopathy (HIE), which is when permanent brain damage occurs and this can lead to seizure disorders or cerebral palsy.
For a full-term newborn, the following show what normal values would look like in an umbilical arterial sample:
- PH: 7.18 – 7.38
- PCO2: 32 – 66 (mmHg)
- HCO3: 17 – 27 (mmol/L)
- PO2: 6 – 31 (mmHg)
- Base excess: -8 – 0 (mmol/L); (Base deficit: 0 – 8)
For a preterm newborn, the following show what normal umbilical arterial values look like:
- PH: 7.14 – 7.4
- PCO2: 32 – 69 (mmHg)
- HCO3: 16 – 27 (mEq/L)
- Base excess: -7.6 – 1.3 (mEq/L)
In PCO2 and PO2, the P stands for “partial pressure,” the measure for these gases.
How is Blood Gas Interpreted?
Each of the following could cause a low pH/fetal acidosis:
- High PCO2
- Metabolic acidosis
- Mixed academia
How Does Fetal Hypoxemia Occur?
There are three different ways in which fetal hypoxemia can occur, which include:
- If there is a lessened amount of oxygen being delivered to the placenta, fetal hypoxemia can occur.
- If there is a reduced transfer of oxygen going across the placenta from the maternal side to the fetal side, fetal hypoxemia can occur.
- If there is a lessened transporting of oxygen by fetal circulation, fetal hypoxemia can occur.
Artery Cord Blood Sample and Acidosis in the Fetus or Newborn
In the majority of newborns who are severely asphyxiated, when they are born, perfusion is poor to nonexistent. This also includes poor umbilical circulation too. The umbilical arteries only reflect the fetal tissue status until the flow in them has ceased. Any lactic acid that came from hypoxia/anoxia at the tissue level will not be cleared to go to central circulation, which includes the umbilical arteries. Therefore, if a fetus or newborn is asphyxiated, their cord gas sample could severely underestimate the acidosis. Once the baby is resuscitated, their circulation gets better and the tissue lactic acid is cleared into the central circulation. Since the lactic acid entered the central circulation, the postnatal base deficit that was received from the asphyxiated newborn during the first hour after they were born is often found to be higher than in the umbilical cord blood gas. Blood gas is an extremely accurate predictor of neurological outcomes.
How are Umbilical Cord Gases Used in Litigation?
There are many different times in which umbilical cord blood cases can be used in litigation. Hospitals may try to use normal umbilical cord gas results in order to defend themselves in a case. However, there are numerous reasons why a baby who suffered asphyxia/hypoxia could have received a normal cord gas:
- The baby may have had poor circulation and perfusion right after they were born
- The baby may have received invalid results due to an error in how the cord gas was drawn, stored or analyzed
- The baby may have suffered a head injury while being delivered that caused ischemia in their brain
In addition, there are many different technical errors that can also have an effect on the umbilical cord gas results. In fact, around 18-20% of cord gas results are not valid because of a technical error.
Free Consultation with a Chicago Birth Injury Attorney
RB Law has experience handling birth injury cases. Umbilical cord gas results can play a very important role in litigation and it is imperative that you obtain the legal services of an attorney with experience in this area. RB Law’s proficient attorneys have the necessary skills and experience to know what to look for in a medical record in order to determine if a cord gas sample was valid and accurate in reflecting the baby’s condition when they were born.
If you have questions regarding your birth injury case, contact us today for a free consultation at (312) 458-1000, 24 hours a day, 7 days a week.