Treatment of Burned Mice With Hyperbaric Oxygen Reduces Mesenteric Bacteria but Not Pulmonary Neutrophil Deposition

Abstract

Hyperbaric oxygen (HBO) is used but unproven for many conditions, including burns. We hypothesized that HBO therapy might increase oxygen delivery to intestine during burn shock and decrease mucosal injury. University research laboratory. We studied the effects of HBO therapy (100% oxygen at 2.4 atm absolute) on mesenteric bacterial colonies (MBCs) in mice following 32% total body surface area burns. MBCs were counted 24 or 48 hours postburn by culturing mesenteric tissue. Intestinal histologic features were examined, acid-base balance was measured, and pulmonary neutrophil deposition was estimated by lung myeloperoxidase content. HBO delivered in a compression chamber. Numbers of mice with MBCs. With twice-daily HBO treatments, each treatment lasting 1.5 or 2 hours, fewer burned mice had MBCs. Three HBO treatments within 24 hours produced seizures, death, and increased numbers of mice with MBCs. Numbers of mice with MBCs were not influenced when compressed air (2.4 atm absolute) or 100% oxygen (1 atm absolute) was used. Villus histologic findings showed less damage in burned mice that received HBO therapy than in controls. Metabolic acidosis was not affected by HBO therapy, nor were lung myeloperoxidase levels. HBO therapy was associated with reduced numbers of mice with MBCs after burn injury and reduced histologic evidence of mucosal damage, but lung myeloperoxidase levels and metabolic acidosis were not affected. HBO therapy may increase oxygen delivery to ischemic intestine and improve cellular metabolism; alternatively, increased tissue oxygen 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.