Different mechanisms are involved in the pathogenesis of IDH including acute central hypovolemia, may be precipitated by rapid or excessive ultrafiltration that lead to intravascular volume depletion beyond the level of hemodynamic compensatory response. Other proposed mechanisms of intra vascular depletion are volume shift into the extra-vascular space due to rapid reduction in plasma osmolality, slow and incompatible vascular refilling rate and incorrectly low prescribed dry weight.