The purpose of this text is to assist clinicians in better
understanding the indications for testing umbilical cord blood gases,
in recognizing the pitfalls involved in collecting and handling specimens,
and in correctly interpreting umbilical cord blood gas values.
To illustrate these points, I use a series of clinical cases drawn
from actual experience with patients. The information is presented
by category, and most
often each successive case within the category is of increasing complexity.
Some of the cases are old and some relatively new. The care provided
was not necessarily
optimal or even acceptable. As with every endeavor, regular practice produces
better results. In many situations, more than one interpretation of umbilical
cord gases is possible. Of critical importance is the reasoning behind the
interpretations. In general, much additional information is provided,
both antenatal and postnatal,
along with the blood gas results. Of course, not all of this information is
available as the baby is being delivered; however, the goal is
correct interpretation of
cord blood gas results. It is important to make sense of the data, not simply
to note the presence of respiratory or metabolic acidosis or mixed acidosis.
Fairly often, this requires integrating information about the fetal monitoring
strip, details of the delivery, the follow-up blood gas results taken directly
from the infant and other post-delivery information.
In each example, the clinical and laboratory data are presented first,
with my own interpretation presented on the following page. This
will allow readers
compose their own thoughts prior to reading my conclusions and, more importantly,
to develop the reasoning behind them.
The objectives of this text are to help the reader to:
(1) Become familiar with normal umbilical cord blood gas values;
(2) Understand the usual relationship between pH and blood gas values found in
the umbilical vein and the umbilical artery;
(3) Recognize how best to interpret the results when technical problems have
(4) Recognize patterns of abnormal umbilical cord blood gas values and understand
(5) Recognize when asphyxia has been associated with delivery and when it has
(6) Be able to decipher even complex issues in the interpretation of umbilical
cord blood gas results, and,
(7) To boldly interpret where no one has interpreted before.
Following each of the first
two sections and the interpretation of each case presentation, “Key Points” are
Jeffrey J. Pomerance, MD, MPH