Question

A young child presents with respiratory distress, worsening over 2 days. Blood gases show a pH of 7.25, a PCO2 of 7.5kPa, a PO2 of 8.5kPa, and a base excess of -4. Which of the following interpretations is correct? 1) Results are consistent with bronchopulmonary dysplasia. 2) Blood gases suggest type 1 respiratory failure. 3) Immediate intubation is required. 4) Results are consistent with late severe asthma. 5) Bicarbonate may be necessary to correct the acidosis.

Answer 1

Answers-4 In interpreting blood gas results, the following sequence may be useful: Inspect the pH: Is it low, normal or high? Inspect the CO2: Is it low, normal or high? Inspect the PO2: Is it low, normal or high? If the pH is low then an acidosis is present, and inspecting the CO2 will enable you to determine whether this is due to respiratory or metabolic causes. Inspecting the PO2 will tell you whether the child is hypoxic or not. In this case, the pH is reduced, and the CO2 is high, with a base deficit of only -4, insufficient to explain the acidosis from metabolic causes. This is, therefore, a respiratory acidosis, and the PO2 is also a little low suggesting type 2 respiratory failure. Possible causes would include pneumonia, early hyaline membrane disease, ARDS. In asthma, the initial stages show a low CO2, with this climbing only as a pre-terminal event. The results would therefore be consistent with late severe asthma. In bronchopulmonary dysplasia, there is usually long-term CO2 retention with compensatory increase in bicarbonate leading to a positive base excess and normal pH. Bicarbonate is usually only considered if the base deficit exceeds about -8 or 00.