[Comparison of the protective prorerties of St. Thomas', Tyers', and Bretschneider's cardioplegic solutions in the neonatal rabbit heart].

Many studies suggest that single-dose and multidose cardioplegia are protective in the ischemic adult heart, but in the neonatal heart single-dose cardioplegia is only protective, whereas multidose cardioplegia is damaging. We examined three clinically used cardioplegic solutions to compare the protective properties of single-dose and multidose cardioplegia in the neonatal rabbit heart (aged 7 to 10 days). The clinical solution studied were St. Thomas', Typers' and Bretschneider's solutions. In isolated working hearts (n = 8/group), cardiac function was assessed prior to 10 hours of ischemia (20 degrees C) and again after 35 min reperfusion (15 min Langendorff, 20 min working). All hearts received a pre-ischemic infusion (10 ml) of cardioplegic solution. The cardioplegic solution was given either as a single infusion (single-dose) or as repeated infusions (multidose) with 5 ml of cardioplegic solution every hour. The changes in coronary vascular resistance (CVR) during repeated cardioplegic infusions were measured in the multidose groups. During 15 min of Langendorff reperfusion, creatine kinase (CK) leakage and CVR were evaluated in all hearts. The results revealed that single-dose cardioplegia provided significantly better functional recovery than multidose cardioplegia in hearts given St. Thomas' or Tyers' solutions, while using Bretschneider solution single-dose cardioplegia Tended to provide better functional recovery. Post-ischemic CK leakages were higher in hearts given Bretschneider's solution in both single-dose and multidose cardioplegia. In hearts given St. Thomas' and Tyers' solutions, post-ischemic CVR in the single-dose group is lower than that in the multidose group, whereas post-ischemic CVR was lowest in the multidose group using Bretschneider's solution. Among multidose groups, CVR prior to reperfusion was lowest in Breschneider's solution as well. In conclusions, these results confirmed that, using the clinical solutions studied, single-dose cardioplegia provided better functional recovery than multidose cardioplegia in the neonatal rabbit heart. However, low CVR in Bretschenider's multidose cardioplegia suggested the better protection in coronary vasculature although functional recovery was poor.