Myocardial metabolism and efficiency after warm continuous blood cardioplegia

Background. Warm continuous blood cardioplegia (WCBCP) has been recommended during prolonged cardiac arrest to minimize functional deterioration. Myoc ardial metabolism and efficiency after this cardioplegic modality are not w ell described. Methods. Substrate oxidation, blood now, and myocardial function were measu red before, during, and after 3 hours of WCBCP in 7 pigs. Results. Free fatty acid and glucose oxidation decreased by 60% +/- 3.8% an d 94% +/- 1.2%, respectively, during cardioplegia (both p < 0.05) and incre ased to 62% +/- 28% and 122% +/- 62% of baseline during the early recovery phase (p < 0.05 for glucose). One hour after WCBCP oxidation rates were sim ilar to baseline. The transient postcardioplegic increase in substrate oxid ation was associated with a 43% +/- 23% elevation of oxygen consumption (MV O2) compared with baseline and a 62% +/- 18% increase in myocardial blood f low. Cardiac output and mean arterial pressure did not change significantly after WCBCP, although myocardial function (stroke work, left ventricular e nd-systolic pressure, end-diastolic pressure, contractility, and efficiency ) was depressed (p < 0.05). End-diastolic pressure and contractility improv ed from early to late phase of recovery, whereas the other indicators of ve ntricular function remained depressed. Conclusions. Myocardial substrate oxidation was preserved after 3 hours of WCBCP, although ventricular function was moderately impaired. Thus, WCBCP w ith a seemingly normal substrate and oxygen supply was associated with a re duced cardiac efficiency. (C) 2000 by The Society of Thoracic Surgeons.