How should a neonatal/pediatric specialist interpret umbilical arterial blood gas results indicating pH 7.28 and PaCO2 49 torr from a term infant on room air?

The interpretation of umbilical arterial blood gas results showing a pH of 7.28 and a PaCO2 of 49 torr indicates an acid-base imbalance. In this case, a pH of 7.28 is below the normal range, which typically hovers around 7.35 to 7.45 for neonates. A PaCO2 level of 49 torr is also elevated, indicating a respiratory contribution to the acid-base status.

The correct answer reveals a condition that is not typical for a healthy term infant on room air, as normal arterial blood gas values would include a pH within the normal range and a PaCO2 closer to 40 torr. Therefore, assessing the values indicates an acidemia situation rather than normal physiological ranges.

In this setting, the elevated PaCO2 suggests that the infant may be retaining carbon dioxide, leading to respiratory acidosis. Without the compensation from metabolic factors (which would involve changes in bicarbonate levels), this condition is characterized as uncompensated. A compensated state would involve the kidneys adjusting bicarbonate levels to offset the respiratory acidosis, which does not apply here given the presented values.

Overall, when interpreting these results, the focus is on understanding that the infant is in a