PREVENTION OF THE HYPOXIC REOXYGENATION INJURY WITH THE USE OF A LEUKOCYTE-DEPLETING FILTER

Objectives: Recent studies have shown that an injury occurs when the h ypoxic heart is suddenly reoxygenated (as occurs with cardiopulmonary bypass), resulting in myocardial depression, impaired oxygenation, and increased pulmonary vascular resistance, We hypothesize that this inj ury is, in part, due to oxygen-derived radicals produced by activated white cells and may therefore be ameliorated by limiting leukocytes in the bypass circuit, Methods: Fifteen neonatal piglets underwent 60 mi nutes of ventilator hypoxia (inspired oxygen fraction 8% to 10%), foll owed by reoxygenation with cardiopulmonary bypass at an inspired oxyge n fraction of 100% for 90 minutes, In nine piglets (group I) our routi ne bypass circuit was used with no modifications, and in six piglets ( group 2) a leukocyte-depleting filter (Pall BC-1; Pall Biomedical Prod ucts Corporation, Glencoe, N,Y,) was inserted in the arterial line to lower the neutrophil count, Six additional piglets underwent 90 minute s of bypass without hypoxia (cardiopulmonary bypass controls), Postbyp ass myocardial and pulmonary function was assessed by pressure volume loops, arterial/alveolar ratio, and pulmonary vascular resistance inde x, Results are expressed as a percentage of control, Results: By compa rison with group 1 piglets (reoxygenation, without a filter), hypoxic piglets undergoing reoxygenation with a leukocyte-depleting filter (gr oup 2) had improved myocardial systolic function (88% vs 52%; p < 0.05 ), diastolic compliance (175% vs 275%; p < 0.05), and preload recruita ble stroke work (91% vs 54%; p < 0.05); had better preservation of the arterial/alveolar ratio (97% vs 74%; p < 0.05); and had less increase in pulmonary vascular resistance (229% vs 391%; p < 0.05), Furthermor e, leukocyte filtration prevented adenosine triphosphate depletion or a change in tissue antioxidants, Conversely, unprotected piglets (grou p 1) exhibited lower levels of adenosine triphosphate and significant loss of tissue antioxidants. Indeed, the results in the leukocyte-filt ered piglets (group 2) were nearly identical to those of piglets subje cted to bypass without hypoxia (controls), Conclusions: (1) This study demonstrates that a major component of the injury that occurs when th e hypoxic heart is abruptly reoxygenated is caused by oxygen radicals produced by white blood cells; (2) this injury can be prevented by a l eukocyte-depleting filter; and (3) avoidance of this injury improves p ostbypass myocardial and pulmonary function, These data suggest that l eukocyte depletion should be used routinely in all children undergoing operations for cyanotic heart disease or extracorporeal membrane oxyg enation.