Single-dose versus multi-dose cardioplegia in the immature rat heart: studies with normothermic and hypothermic ischemia.

The efficacy of cardioplegia in the neonatal heart has been questioned and some studies have suggested that, in the rabbit, multi-dose hypothermic cardioplegia may be damaging. We have therefore compared the protective properties of multi-dose and single-dose cardioplegia in the immature rat heart with normothermic and hypothermic ischemia. Isolated Langendorff perfused hearts (n = 6 per group) from 8-10 day-old rats, were arrested with a single-dose (2 min at the onset of ischemia) or multi-dose (2 min at onset of ischemia and repeatedly throughout ischemia) of warm (37 degrees C) or cold (10 degrees C) St Thomas' Hospital cardioplegic solution. The hearts were then subjected to 1 h of normothermic global ischemia or 24 h of hypothermic ischemia, followed by normothermic reperfusion of 30 min. In the normothermic studies the post-ischemic recovery of left ventricular developed pressure was 44 +/- 6% of its pre-ischemic value with single-dose cardioplegia versus 56 +/- 4% with multi-dose (cardioplegic infusion every 15 min). In the hypothermic studies the trend was in the opposite direction; the postischemic recovery of left ventricular developed pressure was 46 +/- 2% in the single-dose group, whereas in the multi-dose (cardioplegic infusion every 6 h) group the recovery was 28 +/- 3% (p < 0.05). Thus, in accord with other studies in other species we have demonstrated that multi-dose cardioplegia fails to afford any substantial additional protection when compared with single-dose cardioplegia. Under conditions of extended hypothermia there may even be a detrimental effect of multi-dose cardioplegia.