    Retrograde Cerebral perfusion was described in 1980 as a treatment for massive air embolism during CPB ( Mills and Ochsner1980). RCP provides several theoretical advantages.The technique allows for smooth cerebral cooling esay "de-airing"of the brachiocephalic vessels, the potential for limiting cerebral emboli, the ability to flush harmful neurological toxins and other byproducts of ischemic metabolism, and the possibility of direct cerebral matabolic sustrate delivery.
   The application of retrograde cer4ebral perfusion varies from one center to another and from one experiment to another.
RCP techniques can divided into four types (Nojima et al.1994):
1 RCP via the superior vena cava 9SCV) with the inferior vena cava (IVC) occluded and drainage from the aorta.
2 RCP via the SCV and systemic flow via the femoral artery with dranage from the ICV and aorta.
3 Retrograde perfusion via the SCV and Ivc with drainage via the aorta ( total body retrograde perfusion)
4 RCP by raising the central venouse pressure (CVP) with the patient in the Trendelenburg position.
    RCP has been associated with cerebral adema, in which excessive venouse pressure is generated, excessive RCP infusion pressure has olso been associated with decreased cerebral blood flow caused by increased intracranial presure (Usui et al. 1996) and destruction of the blood-brain barrier, and has been suggested that a pressure of 20 mmHg (Nojima et al. 1994) or 25 mmHg provides the maximum retrograde cerebral flow with the least chance of producing increased intracranial pressure and cerebral edema.
     According to currently available information,
the use of RCP for cerebral protection during HCA in the clinical setting is safe when flow rates and CVP and intracranial pressures are maintained at relatively low levels. Even if the only clinical benefits of RCP are its maintenance of cerebral hypothermia and the flushing of air and particulate emboli from the arterial circulation, thereby reducing the risk of embolism, its continued use and investigation would still be justified. ( Coselli 1997).