Effects of manganese superoxide dismutase, when given after inhalation injury has been established

Objectives: To determine whether treatment with manganese superoxide dismutase (MnSOD), given intravenously after inhalation injury has been established, improves oxygenation and lung fluid balance. Design: Randomized, controlled intervention trial. Setting: University research laboratory. Subjects: Twenty-four chronically instrumented awake ewes with lung lymph fistulas. Interventions: After smoke inhalation with 48 breaths of cotton smoke, the animals were assigned randomly to a control group (n = 6) or a treatment group, receiving 1000 units of MnSOD/kg (n = 6), 3000 units of MnSOD/kg (n = 6), or 9000 units of MnSOD/kg (n = 6) intravenously 1 hr after smoke inhalation. Measurements and Main Results. Different from the other three groups, in the group that received 3000 units of MnSOD, cardiac output and PaO2/FIO2 ratio did not significantly decrease throughout the experimental period. Apart from higher oxygen consumption in the group receiving 3000 units of MnSOD 24 hrs after smoke inhalation (263 +/- 44 mL/min vs. 182 +/- 36 mL/min; p < 0.05), no significant differences between treatment groups and control group were observed. Conclusions: Treatment with MnSOD given after smoke inhalation seems to be less effective then pretreatment with MnSOD, which was reported in previous studies to reduce the degree of inhalation injury.