A cardioplegic agent delivery system 10 comprises a syringe pump 26 for providing cardioplegic agent into a carrier fluid of a perfusion system, a flow sensor 20 for sensing a flow of the carrier fluid in cardioplegia circuit 12, and an interlock responsive to the flow sensor. The interlock provides a feedback loop and prevents operation of the syringe pump in the absence of carrier fluid flow as sensed by the flow sensor. The interlock may provide control and allow activation of the syringe pump only when carrier fluid flow exceeds a threshold level, and may be arranged as a controller 30 linked to the flow sensor 20 via a data channel 38. A pressure sensor 42 and temperature sensor 46 may also be provided. This provides increased safety in a cardioplegic agent delivery system.
