Cardioplegic solutions are used throughout the world, but must undergo careful testing before their clinical application. This study points out the importance of recognizing the hemodynamic changes produced by tested solutions so that appropriate decisions can be made in selecting crystalloid or blood solutions. Examples are provided, in which arbitrary changes made by the well-intentioned surgeon can produce damage through unanticipated alterations that are introduced without prior testing, and then used clinically. Recognition of the advantages and disadvantages of each solution is the underpinning of selection for clinical use so that unanticipated misadventures do not occur. Furthermore, the importance of making solutions in pharmacies with good manufacturing practices can avoid causing problems that would otherwise be prevented. Fundamentally, cardioplegic solutions are direct cardiac medications that must be tested as other drugs are so that unforeseen problems are avoided.