Comparison of single- and multi-dose crystalloid cardioplegia to protect the immature myocardium.

The primary objective of this study was to compare the protective effects of single-dose and multi-dose St. Thomas' Hospital cardioplegic solution number 1 in the ischemic and reperfused neonatal rabbit heart. In addition, the effect of including bicarbonate (a component of St. Thomas' Hospital cardioplegic solution number 2) was also studied. Hearts (n = 8 per group) were excised from rabbits (7-10 days old) and aerobically perfused in the working mode with crystalloid media for 20 min (37 degrees C). After assessing cardiac function, the hearts were arrested by an infusion of cold cardioplegic solution (2 min at 15 degrees C) with or without the addition of bicarbonate (10 mmol). The hearts were then subjected to 6 h of hypothermic ischemia (15 degrees C) and, during this period, some hearts received multiple infusions (2 min/h at 15 degrees C) of cardioplegic solution. All hearts were reperfused for 35 min (15 min Langendorff plus 20 min working), cardiac function was then re-assessed and expressed as a percent of the preischemic value. The coronary effluent, collected during the first 15 min of reperfusion, was assayed for creatine kinase activity. At the end of the reperfusion period, the hearts were freeze clamped and taken for metabolic analysis. With multi-dose cardioplegia (without bicarbonate) the postischemic recovery of cardiac output was 67.0 +/- 6.5% and with single-dose the value was 39.3 +/- 10.0% (NS). The same pattern of postischemic recovery (that varied between 30% and 60%) for aortic flow, stroke volume and stroke work was observed with both multi-dose and single-dose infusion.(ABSTRACT TRUNCATED AT 250 WORDS)