Jeffrey Pomerance, MD, MPH

Introduction

The purpose of this series 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 incorrectly interpreting umbilical cord blood gas values. Most of the text comes from my book: Interpreting Umbilical Cord Blood Gases: For Clinicians Caring for the Fetus or Newborn, 2nd edition, published in 2012.

Some areas have been altered for clarity, and not all of the book will appear in this or future installments.

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. 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 the correct interpretation of cord blood gas results. It is important to make sense of the data, not simply to note the presence of respiratory, metabolic, 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 interpretation presented on the following page. This will allow readers to compose their thoughts prior to reading my conclusions and, more importantly, to develop the reasoning behind them. Some of the clinical presentations occurred many years ago and, not unexpectedly, the standard of care has evolved. For example, initiating use of 100% oxygen as a standard part of resuscitation and use of sodium bicarbonate to correct a base deficit are no longer recommended. Nonetheless, in many of the cases presented, these therapies were employed. Additionally, the clinical expertise of the care providers varied from excellent to poor. Therefore, one should not assume that the care provided represents the state of the art.