A full term neonate is born after a long, difficult delivery. The baby has an APGAR score of 3, so aerial blood is drawn for blood gas studies 3 minutes after delivery. Aerial blood gas studies show a PO2 of 10mmHg, PCO2 of 27mmHg, and pH of 7.09. Which of the following is the best interpretation of these studies?
This is something of a trick question, but it is included to illustrate a specific point of which you should be aware. The biochemistries of neonates, especially in the first minutes to hours of life, can be strikingly different from those of adults. Specifically, the normal range of aerial blood pH at bih is 7.11 to 7.36; the normal range of PO2 at bih is the strikingly low 8 to 24 mm Hg; and the normal range of PCO2 at bih is the low 27 to 40 mm Hg. PCO2 is normally lower for infants than adults. pH may vary over the first few hours of life in infants who subsequently do well from 7.09 to 7.50 (a range broader than repoed "normals" in the question stem, but still not necessarily clinically significant). PO2 can be very low at bih but comes up during the first day of life, when it may still normally be as low as 54 mm Hg.
Markedly decreased PCO2, suggesting hyperventilation
Markedly decreased pH, suggesting acidosis
Markedly decreased PO2, suggesting respiratory failure
Within normal limits