Neonatal Nurse Practitioner Practice Exam

A term neonate with labored breathing, retractions, and respiratory grunting shows an arterial blood gas indicating pH 7.23; PCO₂ 49 mm Hg; PO₂ 36 mm Hg; HCO₃ 19 mEq/L. What does this blood gas represent?

1. Partially compensated respiratory acidosis

2. Metabolic acidosis

3. Mixed acidosis

4. Fully compensated respiratory acidosis

The correct answer is: Mixed acidosis

The arterial blood gas results demonstrate a low pH of 7.23, indicating acidosis. The elevated PCO₂ of 49 mm Hg suggests hypoventilation or respiratory depression, leading to an accumulation of carbon dioxide, which is characteristic of respiratory acidosis. The low HCO₃ of 19 mEq/L indicates a metabolic compensation attempt but is also reflective of the acid-base status in this case. In the context of the clinical presentation, where the neonate exhibits labored breathing, retractions, and grunting, the combination of respiratory distress and the blood gas values leads to the conclusion of mixed acidosis. This means there is both a respiratory component (evidenced by the elevated PCO₂ and low pH) and a metabolic component (indicated by the low HCO₃) contributing to the overall acidotic state. Understanding mixed acidosis in this scenario is essential, as it highlights that not only is the respiratory system contributing to the acidosis, but there is also a metabolic response that is exacerbating the condition. This knowledge is key for formulating an appropriate management plan for the neonate.