Narrow-pore flow behavior of blood cells in cardioplegic suspension

Cardioplegia alters the ionic composition of the myocardium and also the bl ood in a way that may influence the cellular capillary flow behavior. We me asured changes in RBC volume and narrow-pore flow resistance of blood cardi oplegia versus crystalloid medium. Potassium, magnesium and sodium as osmot ic control caused an expected cell shrinkage and reduced the flow resistanc e through 3 mu m pores; however, stressing the osmosis further resulted in increased resistance. No major effects were seen with the 5 mu m filters. T wenty percent blood cells in the cardioplegic medium caused a 360% increase in 5 mu m pore resistance. There were no obvious additional filterability effects of the cardioplegic additives other than their osmotic patterns. Th ere may be a theoretical advantage in having a cell-free medium in terms of flow resistance. Using blood cardioplegia, a limited hypertonicity may be beneficial in reducing the capillary flow resistance of RBC.