NEUTROPHIL-MEDIATED ACUTE LUNG INJURY AFTER EXTRACORPOREAL PERFUSION

A pulmonary injury of varying severity occurs routinely after cardiopu lmonary bypass. We studied the pulmonary complications of partial card iopulmonary bypass in four groups of dogs to better define the injury and to evaluate the efficacy of two interventions (addition of a leuko cyte filter or cyclooxygenase inhibition) on preservation of systemic oxygenation. All animals received a standard anesthetic (pentobarbital , morphine, and vecuronium) and, after sternotomy, three groups of ani mals received 3 hours of partial cardiopulmonary bypass. The animals w ere randomized to receive partial bypass alone (n = 6), indomethacin a nd bypass (n = 5), or a leukocyte filter and bypass (n = 5). A fourth group (n = 5) did not receive bypass and served as a time control. We measured blood gases and also obtained histologic samples to assess th e degree of lung injury. We found that bypass alone caused a significa nt reduction (p < 0.05) in arterial oxygen tension 1 hour after the co nclusion of bypass (175 +/- 53 mm Hg) compared,vith prebypass values ( 357 +/- 41 mm Hg). Pretreatment with indomethacin ameliorated the decr ease in arterial oxygen tension from prebypass to postbypass values (4 77 +/- 50 mm Hg versus 339 +/- 57 mm Hg, respectively). Similarly use of a leukocyte filter reduced the decline in arterial oxygen tension f rom prebypass to postbypass values (440 +/- 71 mm Hg versus 311 +/- 73 mm Hg, respectively). We believe that indomethacin ameliorates the de cline in systemic oxygenation associated with bypass by augmentation o f hypoxic pulmonary vasoconstriction and that the leukocyte filter act ed to reduce pulmonary edema and thereby minimized intrapulmonary shun t.