A pump for rapidly discharging irrigation fluid to a surgical site. The pump includes a cabinet with an opening. Inside the pump there is a static plate and a dynamic plate that extends towards/retracts from the static plate. The space between the plates is a bag well in which a bag containing irrigation fluid can be inserted/replaced through the cabinet opening. A lid covers the opening. A sensor monitors the open/closed state of the lid. A drive motor actuates the dynamic plate. A control unit regulates the actuation of the motor. Only when the lid sensor determines that the lid is closed does the control unit actuate the motor. The dynamic plate can be placed in various open positions relative to the static plate so bags containing different volumes of fluid can be used with the pump.