EFFECT OF HYPERBARIC-OXYGEN ON NEUTROPHIL CONCENTRATION AND PULMONARYSEQUESTRATION IN REPERFUSION INJURY

Objective: To evaluate the effect of hyperbaric oxygen (HBO) on muscle flap arterial neutrophil concentration and pulmonary neutrophil seque stration following ischemia-reperfusion injury in a rat gracilis muscl e microcirculation model. Design: Prospective randomized experimental trials. Setting: Laboratory. Materials: Male Wistar rats weighing 150 to 300 g. Interventions: Gracilis muscle flaps were raised on isolated vascular pedicles. Three groups were evaluated: (1) sham (flap raised , 4-hour observation, no ischemia, no HBO), (2) ischemia control (4-ho ur flap ischemia, no HBO); and (3) ischemia (4-hour flap ischemia) plu s HBO (last 90 minutes of ischemia, 100% oxygen, 2.5 arm absolute). Ma in Outcome Measures: Flap pedicle arterial leukocyte and neutrophil co ncentrations were assessed at 5 and 90 minutes of reperfusion in the 3 groups. Pulmonary neutrophil sequestration was measured in a blinded fashion, using histologic examination and myeloperoxidase assay in the 3 groups at 5 and 90 minutes of reper-fusions. Results: Ischemia prod uced an increase in pedicle arterial leukocyte and neutrophil concentr ations in blood flowing to the gracilis muscle flap; administration of HBO significantly reduced concentration to sham levels (P<.05). There were no significant differences in pulmonary neutrophil sequestration among the experimental groups. Conclusions: In this rat gracilis musc le microcirculation model, the increase in pedicle arterial leukocyte and neutrophil concentrations following ischemia-reperfusion injury wa s significantly reduced to sham levels by HBO treatment. This observed reduction was not attributable to HBO-induced pulmonary sequestration , which did not significantly change with HBO administration. Further investigation is required to elucidate the mechanisms of action of HBO in ameliorating ischemia-reperfusion injury in this model.