Understanding Blood Gases in the NICU
Understanding Blood Gases: A Guide for Parents of Babies with HIE
When your baby is diagnosed with hypoxic-ischemic encephalopathy (HIE), it can feel overwhelming to navigate the medical information and terminology. One term you may hear frequently in the neonatal intensive care unit (NICU) is “blood gases.” Understanding what blood gases are and why they are important can help you feel more informed and involved in your baby’s care.
Digging into your medical records after the NICU to make sense of your own medical care and the state your baby was in when they were born is a common need from families, and is often an important part of processing the journey of HIE.
What Are Blood Gases?
Blood gases refer to a set of tests that measure specific components in the blood, including:
- Oxygen levels (PaO2): The amount of oxygen in the blood.
- Carbon dioxide levels (PaCO2): The amount of carbon dioxide in the blood.
- pH: Indicates how acidic or basic the blood is.
- Bicarbonate (HCO3): A buffer that helps maintain the blood’s pH balance.
- Base excess/deficit: Reflects the metabolic component of acid-base balance.
These measurements give healthcare providers crucial insights into how well a baby’s lungs and circulatory system are functioning, as well as how their body is handling metabolic processes.
Why Are Blood Gases Important for Babies with HIE?
HIE occurs when a baby’s brain doesn’t receive enough oxygen and blood flow around the time of birth, with many different causes. Blood gas tests help:
- Assess Oxygenation: Blood gases reveal whether a baby’s oxygen levels were low during or after birth. Low oxygen levels can indicate how severely the brain and other organs may have been affected.
- Evaluate Acid-Base Balance: During oxygen deprivation, the body produces excess acid, leading to a condition called acidosis. The pH and base deficit values from blood gas tests help assess the severity of acidosis.
- Guide Treatment Decisions: Blood gas results help doctors decide on interventions such as oxygen needs, mechanical ventilation, or therapeutic hypothermia (cooling therapy). For example, cooling therapy is a common treatment for babies with HIE to reduce the risk of long-term brain injury, and blood gas results play a key role in determining eligibility for this therapy.
When Are Blood Gases Measured?
For babies with HIE, blood gases are often measured:
- At birth: To evaluate the baby’s condition immediately.
- During NICU care: To monitor progress and adjust treatments as needed.
Blood gases may be taken from different sources:
- Umbilical cord blood: Collected immediately after birth.
- Arterial blood: Taken from an artery, often through a small catheter.
- Capillary blood: Taken via a heel prick.
- Venous blood: Taken from a vein.
How to Interpret Blood Gas Results
While the numbers on blood gas tests may seem complex, here are a few key points:
- Normal pH: Around 7.35-7.45. Lower pH indicates acidosis.
- PaO2 (oxygen): Typically 75-100 mmHg in healthy term babies. Lower values suggest oxygen deprivation.
- Base excess/deficit: A significant base deficit (e.g., more negative than -10 mmol/L) may indicate severe oxygen deprivation.
Your baby’s care team should explain these results in detail and discuss what they mean for your baby’s condition and treatment plan. Sometimes they may be unsure of how much information may be “too much” in the NICU. But never be afraid to ask for more details if you would like more, and never be afraid to write things down, or ask if there’s information they can provide in written format to help you read and understand these complex topics.
Questions to Ask Your Care Team
As a parent, it’s natural to have questions. Here are a few you might consider asking:
- What do my baby’s blood gas results mean?
- How often will blood gases be monitored?
- How are these results guiding my baby’s treatment?
- Are there any changes in my baby’s condition based on the latest blood gas results?
Supporting Your Baby’s Journey
Blood gases are just one piece of the puzzle in understanding and treating HIE. While it can be daunting to learn new medical terms and concepts, building your health literacy empowers you to be an active participant in your baby’s care. Remember, your care team is there to support you and answer your questions every step of the way.
References:
- Umbilical Cord pH, Blood Gases, and Lactate At birth: normal Values, Interpretation, and Clinical utility. Olofsson P., American Journal of Obstetrics and Gynecology. 2023;228(5S):S1222-S1240. doi:10.1016/j.ajog.2022.07.001.
- Hypocarbia Is Associated With Adverse Outcomes in Hypoxic Ischaemic Encephalopathy (HIE). Devi U, Pullattayil AK, Chandrasekaran M., Acta Paediatrica (Oslo, Norway : 1992). 2023;112(4):635-641. doi:10.1111/apa.16679.
- The Term Newborn: Evaluation for Hypoxic-Ischemic Encephalopathy., Bonifacio SL, Hutson S., Clinics in Perinatology. 2021;48(3):681-695. doi:10.1016/j.clp.2021.05.014.
- Preliminary Case Control Study to Establish the Correlation Between Novel Peroxidation Biomarkers in Cord Serum and the Severity of Hypoxic Ischemic Encephalopathy., Chafer-Pericas C, Cernada M, Rahkonen L, et al., Free Radical Biology & Medicine. 2016;97:244-249., doi:10.1016/j.freeradbiomed.2016.06.006.
- Improvement in the Prediction of Neonatal Hypoxic-Ischemic Encephalopathy With the Integration of Umbilical Cord Metabolites and Current Clinical Makers., O’Boyle DS, Dunn WB, O’Neill D, et al., The Journal of Pediatrics. 2021;229:175-181.e1. doi:10.1016/j.jpeds.2020.09.065.
