[Experimental study on the optimal potassium and magnesium concentrations in the cardioplegic solution]

Minimum concentration of potassium and magnesium in cardioplegic solution to get cardiac arrest was studied. The isolated rat hearts were perfused by Langendorf perfusion with Modified Krebs-Henseleit bicarbonate buffer solution, and their heart rates were measured. The perfusion of infusate of 15 mM per liter of K-aspartate stopped the heart beat completely, and as the same way it was necessary 25 mM per liter of MgCl2 to get cardiac arrest. By their combination, however, heart was arrested with infusate of 10 mM per liter of K-aspartate and 15 mM per liter of MgCl2, which were lower concentration than K-aspartate or MgCl2 alone. In order to determine the optimal concentration of potassium and magnesium in cardioplegic solution, the isolated rat hearts were preserved in relatively disadvantageous condition; such as 37 degrees C of infusates, non-oxygenation, continuous perfusion and perfusion pressure 50 cmH2O during 120 minutes. Sixty isolated rat hearts were divided into eleven groups. Each group received a different proper combination of KCl (5.9, 15, 25, 40, 60 mM/L) and MgCl2 (1.2, 13, 25, 33, 50 mM/L) in cardioplegic solution. Using the isolated working rat heart apparatus, hemodynamic indices after 120 minutes preservation were compared with control values of the same hearts, and their percent recoveries were compared with one another. In conclusion it appears that in the isolated working heart model combination of KCl 40 mM/L and MgCl2 13 mM/L in Basic-Modified-Krebs-Solution might offer the best myocardial protection of all combinations tested.