The effects of hyperoxia during fulminant sepsis

Although adequate tissue oxygenation is essential to maintain cellular metabolism, the use of hyperoxia to improve oxygen delivery or to improve metabolic performance is controversial. For example, supplemental inspired oxygen is reportedly beneficial in the treatment of some experimental infections; however, oxygen therapy also has well-documented adverse side effects. To evaluate the effect of increased inspired oxygen concentration (FIO2) in animals with fulminant sepsis, 117 Sprague-Dawley rats underwent cecal ligation and puncture. Animals were then exposed to an FIO2 of either 0.21, 0.4, or 0.8. Twenty sham-operated controls had no mortality with any FIO2. Increasing the FIO2 increased mortality from 70% to 85% in animals receiving 40% O2, and to 100% in those receiving 80% O2. Autopsies revealed mild pulmonary oxygen toxicity with 80% O2 exposure in both control and septic animals, but normal lung histologic appearance in animals receiving lower levels of oxygen. Arterial blood gases documented maintenance of oxygenation and ventilation. Thus, pulmonary oxygen toxicity does not appear to be the mechanism for increased mortality. Supplemental oxygen may worsen, rather than improve, survival after fulminant infection.