The objective of the proposed studies is to evaluate the multisystem adverse effects of the cardiopulmonary bypass (CPB) and to test the role and efficacy of newly developed ultrafiltration and leukocyte depletion techniques and specific pharmacologic inhibitors for their attenuation. We hypothesize that: a) primary mechanisms of inflammatory response due to CPB are activation of humoral (complement, plasmin/kallikrein) and cellular (granulocytes, platelets) cascades which through the positive feedback lead to the production of oxidants/oxyradicals with a shift in the redox potential; b) inflammatory responses can be attenuated, and myocardial function improved by use of modified ultrafiltration techniques and specific pharmacological inhibitors. We will study patients (adults, 25% minorities, 25% females) and experimental animals (pigs, 15-20kg) to accomplish the following specific objectives: 1. To determine whether the damaging effects of CPB are attenuated by the use of mechanical devices: a) ultramicro filter; b) leukocyte depletion filter; c) heparin coated CBAS equipment (Carmeda); and specific pharmacological inhibitors: a) aprotinin (anti-proteolytic agent); b) Futhan (C5a inhibitor), c) endogenous complement inhibitory factor (ECIF) discovered by us; d) phytic acid (hydroxy radical scavenger, metal chelator, anti-hemolytic agent and antioxidant) and e) redox agents to control electrochemical redox potential (N-acetyl cysteine, ascorbic acid, and phytic acid). 2. To define and quantify the individual role played by various pathways: complement activation (C3a, C5a and TCC), neutrophil infiltration (superoxide production by zymosan, PMN elastase, platelet activating factor PAF), oxidant/oxyradical production (O2, OH, free Fe, plasma Hb, lipid peroxide MDA), platelet and coagulation cascades activation (thromboglobulin TG) and fibrinopectin A (FPA), and arachidonic acid (AA) metabolites (TXB2 and 6 keto-PGF1a). 3. To determine the true identity of the free radicals (FR) produced during CPB with our newly developed spin trap-HPLC techniques: a) 4- pyridyl-1-oxide-N-t-butylnitrone (POBN) for O2; b) phenyl-t-butyl nitrone (PBN) for OH and c) electron paramagnetic resonance (EPR) measurements. We seek to find if they are really superoxide/hydroxy radicals or other oxidants (active metal-protein/nucleotide complexes, ferryl radicals Fe2+O2-ADP) which mimic OH. 4. To determine biochemical parameters, FR content, MDA, CK, LDH in the myocardial tissue after CPB in pigs and to correlate with hemodynamic and functional changes of the LV during and after CPB, in particular with respect to the LV systolic and diastolic function. The proposed studies using individual or combined mechanical filters and pharmacological inhibitors will enable us to dissect and determine the specific role played by each of the individual pathways listed, and establish the appropriate methods for attenuation of multisystem damaging effects of CPB.
| Rao, S K; Palazzo, R S; Metz, H N et al. (1997) Redox potential measurements of plasma in patients undergoing coronary artery bypass graft and its clinical significance. J Pharmacol Toxicol Methods 38:151-6 |
