EFFECTS OF EARLY AND DELAYED WOUND EXCISION ON PULMONARY LEUKOSEQUESTRATION AND NEUTROPHIL RESPIRATORY BURST ACTIVITY IN BURNED MICE

Background. Tissue myeloperoxidase (MPO) is a marker of neutrophil (PM N) accumulation in tissues (leukosequestration). We measured MPO in th e livers, guts, and lungs of mice after burn injury and studied the ad ditive effect of burn excision on lung MPO. Lung histologic characteri stics une also examined. PMN respiratory activity was assessed by meas uring intracellular H2O2 content. Methods. Mice received 32% total bod y surface area (TBSA) burns; some underwent burn excision followed by wound closure with allograft skin, either immediately or 48 hours afte r burn. Tissue MPO was measured by a colormetric assay, and intracellu lar H2O2 was quantified by flow cytometry. Results. MPO was elevated i n lungs 8 to 24 hours after born (p < 0.05) but not In the liver or il eum. Other burned mice received either immediate or 48-hour-delayed wo und excision and allografting. In controls a similar-size area was exc ised and grafted with normal or burned skin. Burned animals had increa sed lung MPO compared with nonburned animals (p < 0.05). Highest lung MPO levels were seen after burn/immediate excision (p < 0.001). Lung M PO levels were not different comparing unburned mice undergoing skin e xcision and grafting with either nonburned or burned skin. When burn e xcision was delayed 48 hours, lung MPO was increased moderately (p < 0 .05) but remained far below levels in mice that were excised immediate ly after burn. PMN influx into lung tissues was confirmed by histologi c examination. PMN H2O2 production. tons increased in burned mice and was additionally increased after immediate wound excision. Conclusions . Although burn injury produces pulmonary leukosequestration, the phen omenon is unrelated to local effects of burned skin. In this experimen tal model immediate postburn wound excision increased pulmonary leukos equestration to higher levels than after burn injury alone, and intrac ellular H2O2 content also increased. Pulmonary leukosequestration may predispose to lung injury, possibly limiting the benefits of wound exc ision performed extremely early postburn.