TREATMENT OF BURNED MICE WITH HYPERBARIC-OXYGEN REDUCES MESENTERIC BACTERIA BUT NOT PULMONARY NEUTROPHIL DEPOSITION

Objective: Hyperbaric oxygen (HBO) is used but unproven for many condi tions, including burns. We hypo thesized that HBO therapy might increa se oxygen delivery to intestine during burn shock and decrease mucosal injury. Setting: University research laboratory. Design and Study Par ticipants: We studied the effects of HBO therapy (100% oxygen at 2.4 a rm absolute) on mesenteric bacterial colonies (MBCs) in mice following 32% total body surface area bums. MBCs were counted 24 or 48 hours po stburn by culturing mesenteric tissue. Intestinal histologic features were examined, acid-base balance was measured, and pulmonary neutrophi l deposition was estimated by lung myeloperoxidase content. Interventi ons: HBO delivered in a compression chamber. Main Outcome Measure: Num bers of mice with MBCs. Results: With twice-daily HBO treatments, each treatment lasting 1.5 or 2 hours, fewer burned mice had MBCs. Three H BO treatments within 24 hours produced seizures, death, and increased numbers of mice with MBCs. Numbers of mice with MBCs were not influenc ed when compressed air (2.4 atm absolute) or 100% oxygen (1 atm absolu te) was used. Villus histologic findings showed less damage in burned mice that received HBO therapy than in controls. Metabolic acidosis wa s not affected by HBO therapy, nor were lung myeloperoxidase levels. C onclusion: HBO therapy was associated with reduced numbers of mice wit h MBCs after burn injury and reduced histologic evidence of mucosal da mage, but lung myeloperoxidase levels and metabolic acidosis were not affected. HBO therapy may increase oxygen delivery to ischemic intesti ne and improve cellular metabolism, alternatively, increased tissue ox ygen may augment killing of translocated bacteria by phagocytic cells. HBO deserves further investigation for burn treatment, but because of the narrow therapeutic window and continued neutrophil sequestration in the lungs, we should proceed cautiously.