FOREARM EXERCISE ON FLOW MEDIATED VASODILATION BEFORE HEMODIALYSIS

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. A well functioning vascular access is a requisite for hemodialysis. The optimal access for hemodialysis is a native arteriovenous fistula created by direct anastomosis of an artery and vein preferably in the forearm of the non-dominant arm. However, only a minority of patients on hemodialysis in the United States have a native fistula. The major reason for this is that native fistulas, particularly in the forearm often fail to mature into a usable fistula. This is particularly true in women and older patients, especially those with vascular disease. Pathophysiologically, the most likely reason for this failure is small vessels that do not dilate sufficiently to accommodate the necessary flow rate to be usable for dialysis and to prevent clotting of the fistula. A recent study has confirmed this hypothesis by showing that fistula outcome is independently associated with artery and vein size and with the ability of the brachial artery to dilate in response to increased flow velocity. The latter phenomenon is known as flow mediated dilation. Flow mediated dilation (FMD) is a measure of the ability of a large conduit artery to dilate in response to an increased velocity of flow through the artery. The increased flow velocity creates an increase in shear stress on the endothelium that releases nitric oxide and produces vasodilation. Thus FMD is a measure of endothelial function and this has been shown to be impaired in people with vascular disease. If FMD of the vessels in the arm could be improved prior to surgical creation of a fistula it might lead to better fistula maturation. Exercise has been shown to improve FMD in other studies but it has never been examined whether forearm exercise can improve FMD in this population. This leads to the present hypothesis that preoperative forearm exercise will increase endothelial-dependent FMD in subjects with ESRD scheduled for an arteriovenous fistula.