A method and various devices are disclosed that facilitates the measurement of hemodynamic parameters by injection of an indicator in an indicator dilution technique using an extracorporeal circuit connected to a patient. Specifically, the invention deals with problems caused by the spike in pressure in an extracorporeal line that result from the injection of a bolus. The method and various devices provide for diversion of blood during an indictor injection process and then return of the diverted blood back into the system after the injection is completed. The variations of the invention use diversion lines, accommodating cases and other devices that are designed to accumulate blood displaced during injection and then returning the blood to the extracorporeal circuit after injection.
