RESUMO
The interposition polytetrafluoroethylene graft conduit has found many uses in the armamentarium of the surgeon who performs vascular access for hemodialysis: when resection of aneurysm or pseudoaneurysm is required, or when an extension loop is required, either to simply lengthen the amount of graft or to circumvent an infected segment after resection. Herein, we have presented yet another use for the interposition polytetrafluoroethylene graft conduit, based on physiologically sound principles and a now proved successful outcome, namely as a surgical alternative for the patient with a hemodynamically unstable hemodialysis fistula resulting in arterial insufficiency. Poiseuille's Law regarding flow of liquids through a tube supports the concept on which our interposition graft is based: v = pi X P X R4/8 X 1 X n where v is the volume escaping per second, P the difference of pressure at the ends of the tube, R its radius, l the length of the tube, and n the coefficient of viscosity. Given the maintenance of all other parameters, if one increases the length of the tube through which blood is flowing, the volume of flow through said tube is simultaneously decreased, and the ischemic symptoms caused by arterial insufficiency are thereby ameliorated.
