Bretschneider's histidine-buffered cardioplegic solution and the calcium paradox

Reperfusion of an isolated heart with calcium-containing solution after a short period of calcium-free perfusion may result in irreversible cell damage (calcium paradox). Experiments were undertaken to determine whether rat hearts could be predisposed to the calcium paradox by perfusion with Bretschneider's calcium-free histidine-buffered cardioplegic solution. Creatine kinase (CK) release during the reperfusion phase was used to quantitate cell damage. Perfusion with cardioplegic solution was performed at 37 degrees and 20 degrees C. Reperfusion after 10 minutes of perfusion with this solution at 37 degrees C resulted in a full calcium paradox. After 120 minutes of perfusion with cardioplegic solution at 20 degrees C, CK release during reperfusion amounted to 30% of the release during a full calcium paradox. This CK release could be further reduced by lowering the coronary flow rate or by adding 50 mumol X L-1 CaCl2 to the cardioplegic solution. It is concluded that a combination of hypothermia, a low coronary flow rate, and a limited duration of exposure to Bretschneider's histidine-buffered cardioplegic solution will minimize the risk of evoking the calcium paradox.