Peripheral collateral blood flow and vascular reactivity in the dog.

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Abstract
The effects of several different procedures on collateral blood flow and vascular resistance were investigated in the dog hindlimb and forelimb. In the hindlimbs with acutely or chronically ligated main arteries, collateral flow could be increased and vascular resistance decreased by vasodilator procedures in a manner qualitatively similar to findings in the vas-culature of limbs with unobstructed arterial inflow. Vasoconstrictor procedures decreased collateral blood flow, but significant increases in collateral vascular resistance occurred only during systemic arterial pressure depression in the acutely ligated dogs. A limited but fully collateral vasculature was evidently present in the acutely ligated fore-limb preparation since vasodilator stimuli lowered local vascular resistance without decreasing collateral resistance. Retrograde blood flow was also evaluated by measuring the blood flow from the femoral artery below its ligation site; O2 studies showed the blood from arteries below an obstruction had not passed through a capillary bed. Measurement of retrograde blood flow by this method was not considered to be reliable for the study of collateral vessel reactivity. Collateral vessels react to various vasoactive procedures in a manner similar to other blood vessels in the limbs. Differences in the reactions of the collateral vasculature reported in this and other studies may be explained by variations in the amount and vasomotor state of the collateral vasculature resulting from the different experimental preparations used.