Continuous arteriovenous hemofiltration is an extracorporeal technique for the treatment of fluid overload and electrolyte disturbances and for the removal of urea nitrogen. This technique is especially applicable in critically ill patients with hemodynamic instability. A special filter and modified hemodialysis blood lines can easily and rapidly be attached to a patient. No special blood access is needed. Fluids and solutes are removed from the patient by ultrafiltration. A net filtration pressure inside the filter causes an ultrafiltrate to form. The extracorporeal circuit can be kept in place for hours or days.