A cardioplegic agent delivery system comprises a supply reservoir 10 for a cardioplegic agent carrier fluid, a delivery channel from the supply reservoir to an outlet 48, and a pump 50 to flow the carrier liquid in the delivery channel above a minimum driving pressure. The supply reservoir is configured to hold carrier fluid below the minimum driving pressure. The pump is a centrifugal pump configured to receive carrier fluid from the supply reservoir and to flow the carrier fluid to the outlet at a flow rate and above the minimum driving pressure for the delivery of cardioplegic agent. A back-flow prevention device may be located downstream of the supply reservoir and the system may include a flow sensor and a pressure sensor. A collapsible bag may function as an intermediate reservoir (40, figure 2).
