A cannulation system (10) for perfusing a patient's circulatory system, includes an inflow cannula (14) having a first end adapted to be connected to said circulatory system and a second end adapted to be connected to a blood pump (19), an outflow cannula (23) having a first end adapted to be connected to the blood pump (19) and a second end adapted to be connected to said circulatory system at a location downstream of the first end of the inflow cannula. The flow of blood from the pump (19) is in series with the normal blood flow of the circulatory system of the patient and creates a localised region of hypertension. FIG. f
