Inspired superoxide anions attenuate blood lactate concentrations in postoperative patients

Objective: Low concentrations of superoxide (O - 2 ) constitute a portion of atmosphere negative ions in the form of O - 2 (H 2 O) n , which has been reported to have a stimulatory effect on superoxide dismutase activity. If superoxide dismutase is activated by inspired negative ions containing O - 2 , aerobic metabolism could be improved. To test this hypothesis, we examined blood lactate concentrations in postoperative patients with or without inhalation of air from a home humidifier that generates O - 2 (H 2 O) n . Design: Prospective, randomized, controlled trial. Setting: Neurosurgical intensive care unit of a general hospital. Patients: Twenty postneurosurgical patients with arterial blood lactate concentrations >1.5 mmol/L were studied and were divided randomly into two groups. interventions: One group received 40 Umin 40% oxygen flow from a home humidifier as an oxygen therapy for 4 hrs, followed by almost the same flow from a jet nebulizer, which generates positive ions, for 4 hrs. The other group received the reverse combination. Measurements and Main Results: During the 8-hr study, arterial blood lactate concentrations were measured every hour. There was a significant difference in the time course of blood lactate concentrations between the groups. In the group in which negative ions were first initiated for 4 hrs and positive ions thereafter, the lactate concentration decreased slightly at 3, 4, and 5 hrs and returned to the baseline concentration thereafter. In the group with the reverse combination, the lactate concentration did not change during the first 4 hrs but decreased thereafter after inhalation of negative ions. Conclusions: Inspired O - 2 attenuates blood lactate concentrations. This may be attributed, in part, to the systemic stimulatory effect on superoxide dismutase activity, which accelerates oxidative phosphorylation in the mitochondria, thus attenuating lactate generation.