Metabolic Markers Evolution During Antegrade and Retrograde Normothermic Blood Cardioplegia

Background: Several studies suggested that the ventricular myocardium is suboptimally protected during retrograde blood cardioplegia.
Methods: Twenty patients (10 patients for subgrups) undergoing an elective valvular replacement mitral and aortic, with right atrial approach, mitral transeptal or tricupid procedures were randomized to receive antegrade or retrograde normothermic blood oxigenated cardioplegia. Astrup determinations (astrup values, lactate production, pH and BE) and ventricular differences in oxygen extraction from separate coronary ostium canulation were monitored during aortic cross-clamping at time at cardioplegic delevery immediately after cross clamping, at first, 20 minutes or 30 minutes of ischemia, after aortic declamping immediately and after 10 minutes. Hemodynamic recovery and postoperative complications were noted.
Results: The preoperative characteristics of the two groups were similar. Lactate production and oxygen extraction in the right ventricular myocardium were higher in the retrograde group. In this group, the right ventricle also extracted more oxygen and produced more lactate and acid than did the left ventricle. A typical cumulative ischemic pattern with progressively decreasing pH, BE values and progressively increasing lactate values could be observed similar in both groups in all patients. It was not the degree of lactate washout, but the lactate concentration at the end of each reperfusion wich increased proportional with ischemic time bettewen cardioplegic administration and after declamping — that correlated significantly with global metabolic recovery time. Nevertheless, the postoperative course was uneventful in both groups.
Conclusions: Despite of value of lactate production, acidosis and oxygen extraction, were more prominent in the right ventricular myocardium during retrograde cardioplegia after declampation, at 10 minutes this value became similar, and clinical and inotropic necesity were similar in this two groups. During antegrade cardioplegia the washout of myocardial metabolites is very efficient and the peak levels of lactate decrease rapidly at the end of cardioplegic administration and after declampation compared with retrograde administration. No diference seems to be seen between retrograde or anterograde cardioplegic administration 10 minutes after declampation. Nevertheless the postoperative course seems to be unproblematic in two series.