Abstract: A cardioplegic controlling and regulating device for the dosed perfusion of cardioplegic perfusion solution in open-heart surgery has a storage container for receiving the cardioplegic solution, which container is part of a scale and can be connected to the heart over a tubular conduit. A pressure-controlled dosing pump which acts on the tubular conduit and cooperates with a second, reversible pump which is constructed as an exhaust pump and is selectively operable synchronously or asynchronously within controllable tolerance limits with the first dosing pump during the perfusion and sustaining of the perfusion. An ultrafilter for the mixture of blood and cardioplegic solution removed from the patient's heart is located in a removal line. An outlet for the blood separated form the ultrafilter is connected by a conduit to a blood storage container and the permeate or filtrate outlet of which ends in a filtrate line or in a filtrate collector vessel.