Posted on: July 16, 2014
The Fourth Vital Sign
By Dr. Rick Stafford
Congrats. You’re having a baby! Whether this is your first, or your fifth, you’ve most likely read everything you need to know about what to expect, and you’ve no doubt gotten advice from well-meaning friends and relatives. But before you take your infant home, doctors will be looking for a few key signs that your child is healthy and ready to leave the hospital. All states require specific tests for newborns to assess for potentially fatal disorders that aren’t otherwise apparent at birth, among them the recently required pulse oximetry assessment. The information below explains its significance.
New to the newborn screening docket, as of 2013, is pulse oximetry screening for cyanotic congenital heart disease (CCHD). Pulse oximetry, which indirectly measures the oxygen level in the bloodstream, has become almost a fourth vital sign (temperature, pulse rate and respiratory rate are the traditional 3 vital signs). New York State health code now mandates pulse oximetry screening for CCHD in all newborns born in New York. Northern Westchester Hospital was proactive in this regard and has been administering the screening since April of 2013.
The right side of the heart pumps blood through the lungs, where it picks up oxygen. Blood returns to the left side of the heart, where it is then pumped to the rest of the body. There are some congenital cardiac defects that impair oxygen delivery to the blood. This results in the delivery of de-oxygenated blood to the body, a condition (cyanosis) that is not compatible with life. Pulse oximetry screening can pick this up in a newborn before he or she becomes critically ill. In a fetus, the circulation is very different. Oxygenated blood comes from the placenta and two shunts; it then circulates around the lungs into the left side of the heart where it flows to the rest of the fetus. Because of this, a fetus with a cyanotic congenital heart defect will not be sick while in the womb.
These shunts are supposed to close within a few hours after birth, and when they do, the babies may begin to get sick. The shunts don’t always close right away and a baby may get sick after being discharged home. This is why applying pulse oximetry screening to a newborn is so valuable. Doctors and nurses normally wait at least 24 hours before administering the screening. Do the test too early and it’s possible those shunts are still working, thus masking the condition. Too late and the baby could become very sick very rapidly.
The test is administered with a sensor that measures and compares the differences in the wavelengths of oxygenated and deoxygenated blood. The sensor is first placed on the baby’s hand and then on the foot, with the expectation that the numbers will be the almost the same. A cardiologist would be called in for a consult if there is a percentage difference of three points or higher, or if the baseline saturation is low. If a diagnosis of CCHD is made, the neonatology team would then work to stabilize the baby and prepare him or her for transport to a large regional center where corrective heart surgery could be performed.
It’s all about early detection, intervention and treatment.
Editor’s Note: Rick Stafford, MD, FAAP is the Chief and Director of Neonatology at Northern Westchester Hospital. Parents looking for more information on this subject should check out the web-site of the American Academy of Pediatrics: www.aap.org