The intraoperative measure of runoff resistance in the canine hindlimb

Long-term survival of femoro-popliteal grafts has been predicted on both graft function and distal vascular bed resistance. The purpose of this study was to demonstrate peripheral resistance as a function of the inherent elasticity (distensibility) of the distal vascular bed. The use of saline perfusate and maintenance of physiologic pressure will supplant such other factors as fluid viscosity, vasomotor tone, blood pressure, and tube dimensions. Our model consisted of Javid shunt insertion in the femoral artery of 13 female dogs distal to an occlusive tie. Saline was perfused in incremental fashion every 30 sec over a 5-min period; femoral pressure measurements were taken at each flow rate (Q) (cc/min). Results show that mean femoral pressure (MFP) varies with Q less than 125 (P less than 0.005) and Q greater than 200 (P less than 0.001). Furthermore, mean resistance (MR) declined precipitously with Q greater than 125 cc/min but at higher Q the MR plateaued (P less than 0.0001). We interpret these results to indicate that at Q less than 125 vasomotor tone is the predominant factor in MR and that saline perfusion abrogated this factor at 125 greater than Q less than 200. At Q greater than 200, MR declined only slightly and, therefore, MFP varied directly with Q indicating that vessel elasticity is the predominant feature of MR after vasomotor tone ablation and that pressure varies directly with flow in a distensible system. Pressure-flow graphs could be obtained prior to femoro-popliteal reconstruction via this quick, simple technique and rapid rises in pressure should indicate poor distal runoff.