Regional circulatory responses to hindlimb work in developing swine.

Circulatory effects of hindlimb work were studied in 29 swine (aged 1 day to 1 month) anesthetized with pentobarbital. Femoral, renal and intestinal blood flow, resistance and autoregulatory capability were determined at different levels of hindlimb oxygen consumption before and during distal sciatic nerve stimulation. Increases in oxygen consumption were accompanied by hyperemia at all ages, but by increased oxygen extraction only in 2-week and 1-month-old animals, without evidence of autoregulation. Blood flow was consistently redistributed from the kidney and small intestine only in neonates. Older animals generally sustained autoregulation of renal and intestinal blood flows throughout experiments. We concluded that hindlimb work evokes age-related adjustments in regional blood flow that reflect the balance of neural and autoregulatory control.