BLOOD-FLOW RATE DURING ORTHOSTATIC PRESSURE CHANGES IN THE PULP SKIN OF THE FIRST-TOE

Objectives: Determination of the local regulation of cutaneous blood f low through nutritive capillaries and through arteriovenous anastomose s of the pulp of the first toe in response to passively induced orthos tatic blood pressure changes in normal subjects and in patients with o cclusive atherosclerotic disease. Material: Six normal subjects, seven patients with unilateral, crural intermittent claudication and six pa tients with unilateral, chronic critical ischaemia. Methods: Blood flo w rates were measured in supine subjects by the heat washout method (t he sum of blood flow rate in arteriovenous anastomoses and blood flow rate in nutritive capillaries) and by the (133)Xenon washout method (b lood flood rate in nutritive capillaries) after local, atraumatic labe lling. Measurements were made with (a) the toe passively elevated to 5 0 cm above heart level, (b) at heart level and (c) passively lowered t o 50 cm below heart level. Results: Autoregulation of nutritive blood flow was present in normal subjects and in claudicants, but the local sympathetic veno-arteriolar axon reflex was absent in both groups. In patients with critical ischaemia blood flow rate was the same in the s upine position and during lowering in arteriovenous anastomoses and in nutritive capillaries. The arteriovenous anastomoses had distinct and characteristic reaction patterns in response to lowering in each of t he three examined groups and to elevation in normal subjects and in pa tients with intermittent claudication (not measured in patients with c ritical ischaemia) Conclusions: The microvascular responses to changes of orthostatic blood pressure differed among the three groups (normal subjects, patients with intermittent claudication, patients with crit ical chronic leg ischaemia). The heat washout method may be used to de tect the functional significance of occlusive atherosclerotic disease.