Regulation of subcutaneous blood flow during head-up tilt (45 degrees) in normals.
Local and remote regulation of subcutaneous blood flow in the forearm and leg was studied during head-up tilt (45 degrees) in 6 young healthy male subjects. Relative blood flow was estimated by the local 133Xe washout technique. Lowering of a leg to a 51% decrease in its subcutaneous blood flow due to a veno-arteriolar reflex elicited by the increase in venous transmural pressure. During head-up tilt subcutaneous blood flow in the arm remaining at heart level decreased by 27%, in the leg blood flow decreased by 50%. Following proximal nervous blockade, head-up tilt did not induce vasoconstriction in forearm at heart level, but blood flow in distal leg decreased by 45%. Thus there was no difference in the vasoconstrictor response in the leg to head-up tilt or lowering of the labelled area by 40 cm. Since head-up tilt caused neurogenically mediated vasoconstriction in subcutaneous tissue, subcutaneous blood flow in the extremities seems to be regulated by remote (baroreceptor) as well as local sympathetic reflex mechanisms (veno-arteriolar reflex).
D000328:Adult; D001340:Autonomic Nerve Block; D005542:Forearm / Q000098:blood supply; D006439:Hemodynamics; D006801:Humans; D007866:Leg / Q000098:blood supply; D008012:Lidocaine; D008297:Male; D011187:Posture; D011311:Pressoreceptors / Q000502:physiology*; D012018:Reflex; D012039:Regional Blood Flow; D012867:Skin / Q000098:blood supply*; D014661:Vasoconstriction
D008012:Lidocaine