Coronary perfusion with a calcium-free solution, followed by reperfusion with a calcium containing solution, may result in acute myocardial cell death and in irreversible loss of the e1ectrical and mechanical activity of the heart. This phenomenon is known as the calcium paradox. A number of cardioplegic solutions that have been developed for clinical practice, are free of calcium (e.g. the Bretschneider solution). Animal experiments have demonstrated that under certain circumstances coronary perfusion with the Bretschneider solution can predispose the heart to the calcium paradox. During cardiac surgery, however, calcium-free cardioplegic solutions can be used without risk of inducing the calcium paradox during
reperfusion of the heart with calcium-containing blood, provided that temperature during cardioplegia is low, and flow and duration of infusion are limited. It is recommended, nevertheless, to avoid the use of calcium-free cardioplegic solutions in clinical practice