CHICAGO — Not only hypoxemia but hyperoxemia, too, is associated with increased mortality in patients with traumatic brain injury, Dr. Daniel P. Davis reported at the annual scientific sessions of the American Heart Association.
The dangers of hypoxemia in the setting of traumatic brain injury (TBI) are well documented. But the increase in bad outcomes associated with hyperoxemia hasn't previously been reported in a clinical population with TBI. The new findings suggest a need to rethink the popular practice of aggressive airway management in such patients, including intubation and ventilation with 100% fraction of inspired oxygen concentration, according to Dr. Davis of the department of emergency medicine at the University of California, San Diego.
He presented a retrospective study of 3,515 patients with TBI in the San Diego County Trauma Registry. Of them, 1,012 were hypoxemic as defined by a partial pressure of oxygen (PO2) below 110 mm Hg, and 358 were hyperoxemic, with a PO2 in excess of 487 mm Hg.
The Trauma and Injury Severity Score (TRISS) was used to calculate each individual's predicted survival, and the hypoxemic patients had an observed survival rate 41% lower than predicted. Hyperoxemic patients were 48% less likely to survive than was predicted by TRISS. And patients with a PO2 in the optimal range of 110–487 mm Hg were 77% more likely to survive than was predicted. This pattern of results persisted even when intubated and nonintubated patients were analyzed separately.
The goal of aggressive airway management with hyperoxygenation is to reverse hypoxia and increase oxygen tension in an effort to counteract regional hypoperfusion and edema. But theoretic concerns exist regarding creation of a hyperoxemic state in the setting of TBI.