Constant-flow perfusion of the hindlimb vascular bed in conscious dogs

Hindlimb vascular bed pressure-flow relationships were evaluated in seven conscious dogs using a newly developed controlled-flow perfusion technique. For controlled-flow perfusion, blood was diverted from a common carotid artery to a roller pump for perfusion of the left hindlimb vascular bed via an artificial vascular graft anastomosed to the left external iliac artery. An occlusion cuff positioned around the external iliac artery proximal to the graft arrested normal hindlimb blood flow during perfusion. Collateral flow was minimized by ligating all other major arteries supplying the left hindlimb. Hindlimb perfusion pressure, measured via the left deep femoral artery, decreased to a plateau value of 19.7 +/- 3.4 mmHg when pump flow was zero. Pressure-flow relationships were evaluated while the dogs were at rest by changing flow in small "square-wave" steps for 3 min each and measuring the steady-state perfusion pressure at each step. The hindlimb was perfused over a wide range of flows (25-450 ml/min) that resulted in perfusion pressures ranging from 40 to 175 mmHg. The hindlimb pressure-flow relationship obtained was indicative of net passive vascular behavior. That is, resistance to flow decreased with increases in flow, such that a curvilinear pressure-flow relationship occurred that was convex to the pressure axis. We conclude that the hindlimb circulation of resting conscious dogs can be perfused using controlled-flow perfusion techniques. These techniques can also be applied to other vascular beds and should be useful for evaluating peripheral vascular responses to drugs and reflexogenic alterations.