Treatment of burned mice with hyperbaric oxygen reduces mesenteric bacteria but not pulmonary neutrophil deposition
M. Tenenhaus, J. F. Hansbrough, R. Zapata-Sirvent and T. Neumann
Department of Surgery, University of California, San Diego Medical Center.
OBJECTIVE: 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. SETTING: University research laboratory. DESIGN AND STUDY
PARTICIPANTS: 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. INTERVENTIONS: HBO delivered in
a compression chamber. MAIN OUTCOME MEASURE: Numbers of mice with MBCs.
RESULTS: 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. CONCLUSION: 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.
