A patient wearable, continuously operating extracorporeal pump apparatus which accesses the patient's arterial venous pressure differential by applying external pressure to a subcutaneous graft that has been cannualized to modulate blood flow through an extracorporeal circuit and to drive the pump for delivering a medicament, such as an anticoagulant, to the site of an intravenous cannula to prevent clogging thereof and also to move a dialysate through a circuit, including a dialyzer and a dialysate rejuvenating cartridge, whereby kidney failure can be treated without recourse to prior art hemodialysis machines found in most treatment facilities. With slight modification, the present invention can be used to remove excess fluids from CHF patients, to remove toxins from the blood in those suffering from liver failure and to facilitate administration of insulin to diabetics and/or glucose to those having hypoglycemia.