Arterial blood gas and acid-base disorders in infants and children with status asthmaticus

The course of arterial oxygen tension (Pao2), pH, carbon dioxide tension (Paco2) and base deficit (negative base excess) was studied in 45 episodes of status asthmaticus occurring in 32 infants and children. The data indicate that arterial hypoxemia occurs in these patients due to alveolar hypoventilation and pulmonary arterial-venous shunts. Three fourths of the patients tested demonstrated a base deficit which was related in part to ketonemia. The Paco2 varied from below normal to 168 mm Hg, and arterial pH varied from 6.89 to 7.41 at the time of peak clinical severity. Clinical signs of respiratory failure associated with a Paco2 above 65 mm Hg occurred in 13 patients (18 episodes), all of whom were successfully managed by mechanical ventilation. These studies indicate the variability in alveolar ventilation and acid-base balance during an asthmatic episode and the need for repeated assessment of arterial pH and blood gases if one is to provide optimal management.