Outcome Measurements: Following blinded random allocation to plasma exchange or control, the treating physicians who report the primary outcome will be aware of treatment assignment. The composite outcome includes death, dialysis dependence and a MDRD GFR calculated from a serum creatinine at 6 months follow-up. The addition of a GFR <30ml/min/1.73m2 to our negative composite outcome reflects a significant increased risk of death, cardiovascular events and hospitalization associated with this degree of kidney impairment.