TISSUE BLOOD-FLOW DISTRIBUTION AND THE EFFECT OF CHRONIC VASCULAR CATHETERIZATION IN THE HIND-LIMB OF THE FETAL LAMB

In six chronically instrumented fetal lambs, hind-limb shin, bone, and muscle comprised 22.5 +/- 1.3, 35.3 +/- 1.6, and 42.3 +/- 1.1% of tot al limb weight, respectively. As estimated using radionuclide-labeled microspheres, blood flow to these tissues averaged 30.4 +/- 4.9, 30.1 +/- 3.3, and 14.0 +/- 3.1 mL . min(-1). 100 g(-1), respectively, and t hey received 29.5 +/- 3.3, 45.3 +/- 3.6, and 25.2 +/- 4.5% of total li mb blood flow. Thus, muscle has a lower blood now in relation to its w eight in comparison with the other tissues, while bone receives the la rgest fraction of hind-limb blood flow. The higher perfusion rate to b one may by due to a high rate of hematopoiesis in late gestation, wher eas muscle flow may be lower than that reported immediately after birt h because of limited limb movement and lack of shivering thermogenesis . There were no significant differences in tissue weights between the limb in which femoral arterial and lateral tarsal venous catheters wer e implanted (nonstudy limb) and the leg that had smaller diameter cath eters placed in the pudendoepigastric artery and vein (study limb). Ho wever, nonstudy limb blood flow was 13.4 +/- 1.8% less than in the stu dy limb, although the flow distribution to hind-limb tissues was not d ifferent between the two Limbs. This suggests that the longer, larger diameter catheters inserted into the nonstudy limb had an adverse effe ct on hind-limb blood flow but not on overall limb growth or blood flo w distribution. More attention should be paid to the effects of chroni c fetal vascular catheterization on the tissues or organs normally per fused by the catheterized vessel.