Red blood cell energy metabolism during cardiopulmonary bypass

Background During cardiopulmonary bypass (CPB) an intracellular ATP deficit could theoretically play a role in changes of erythrocyte shape and deform ability caused by mechanical trauma. We therefore studied erythrocyte energ y metabolism in 12 patients undergoing normothermic CPB for myocardial reva scularization, Methods. Blood samples were collected prior to and 45 minutes after CPB beg inning and analyzed for erythrocyte ATP, ADP, and AMP and their metabolites , erythrocyte NAD and NADP, plasma and whole blood lactate (Lact(p) and Lac t(b) respectively), and whole blood pyruvate (Pyr(b)) Results. Values were expressed as mean+/-standard deviation or median (lowe r and higher quartiles) on the ground of a test for normality. During CPB e rythrocyte nucleotides and their metabolites did not change significantly ( ATP: 60.2+/-12.1 vs 68.3+/-13.0; ADP: 12.2+/-3.6 vs 12.0+/-3.1; AMP: 0.43+/ -24 vs 0.44+/-0.26; adenosine: 0.063 (0.034-0.203) vs 0.77 (0.032-0.221); i nosine: 0.064 (0.023-0.072) vs 0.075 (0.025-0.111); hypoxanthine: 0.330+/-0 .272 us 0.567+/-0.223; xanthine: 0.193+/-0.090 vs 0.220+/-0.095; NAD: 3.149 +/-0.743 vs 3.358+/-0.851; values in mu M/mM packed red blood cell hemoglob in) while NADP increased (2.110+/-0.390 vs 2.433+/-0.288 mu M/mM packed red blood cell hemoglobin; p<0.05). Ringer lactate, with which the extracorpor eal circuit was primed, caused Lactp to increase (1.87+/-0.81 vs 3.27+/-1.1 5 mM/l; p<0.01). Some lactate entered erythrocytes since Lact(p)/Lact(b) ra tio did not change (1.09+/-0.25 vs 1.07+/-0.23) and some was transformed in to pyruvate since Pyrb increased [62.9 (30.3-73.3) vs 100.5 (61.0-146.9) mu M/l; p<0.01]. Lact(b)/Pyr(b), ratio did not change significantly [22.6 (16 .1-40.5) vs 27.9 (17.5-35.2)] so that NAD/NADH ratio and, consequently, the rate of glycolysis were unlikely to change too. Conclusions. Erythrocyte energy metabolism is not affected by CPB, at least during the period of time taken into account in, this study.