CONTINUOUS VERSUS INTERMITTENT WARM BLOOD CARDIOPLEGIA - FUNCTIONAL AND ENERGETICS CHANGES

Background. The aim of this study was to compare the protective effect s of continuous warm blood cardioplegia (CWBC) and intermittent warm b lood cardioplegia (IWBC) in an experimental model of blood-perfused, i solated rabbit heart. Methods. In the CWBC group, cardiac arrest was i nduced by continuous infusion of blood cardioplegia (10 mEq/L KCl) fol lowed by 30 minutes of reperfusion with blood. In the IWBC group, afte r 5 minutes of perfusion with blood cardioplegia (10 mEq/L KCl), coron ary now was abolished for 10 minutes, followed by reperfusion with blo od cardioplegia for 5 minutes. This sequence was repeated three times for a total period of 45 minutes. Finally the hearts were reperfused f or 30 minutes with blood. Results. Infusion of potassium induced a mar ked increase in coronary perfusion pressure (from 50 +/- 3 to 98 +/- 1 mm Hg; p < 0.01), which remained elevated throughout in the CWBC grou p, whereas in the IWBC group, it dropped to 0 during each no-flow peri od. In both groups, cardioplegia resulted in a significant reduction i n oxygen consumption (from 5.5 +/- 0.2 to 0.6 +/- 0.03 mL O-2 . min(-1 ) . 100 g(-1) wet wt; p < 0.01). During CWBC, glucose extraction was s ignificantly reduced (from 152 +/- 10 to 64 +/- 18 mu g . min(-1) . g( -1) wet wt; p < 0.01). Free fatty acid uptake and creatine kinase and lactate release were not affected. During IWBC, in contrast, a transie nt but significant release of creatine kinase (from 643 +/- 254 to 2,2 34 +/- 296 mU . min(-1) . g(-1) wet wt; p < 0.01) and lactate (from 63 +/- 22 to 374 +/- 32 mu g . min(-1) . g(-1) wet wt; p < 0.01) occurre d after each period of ischemia. Despite these metabolic differences, both cardioplegic procedures allowed a prompt and complete recovery of mechanical function and tissue content of high-energy phosphates. Con clusions. Both CWBC and IWBC exert optimal protection in the isolated blood perfused rabbit heart. Thus, IWBC can be safely used to improve visualization of the surgical field.