ADVANCES IN MICROCIRCULATION NETWORK EVALUATION - AN UPDATE

Many methods are available today for clinical evaluation of the blood supply to an extremity or part of an extremity, some of which are exce llent for determining the presence and severity of arterial and venous disorders. These methods, however, do not give any information on the microvascular status of the diseased areas. This is particularly true for the skin circulation, which has a rather complex vascular network with nutritional and thermoregulatory vessels, arteriovenous shunts, etc. The most useful method for clinical evaluation of the skin capill ary circulation is vital capillary microscopy. The skin capillaries in an area with a reduced microcirculation change in structure, and it i s possible to evaluate the viability of the skin by microscopic studie s of these capillary changes. Both morphology and blood flow can be in vestigated. By using different intravital fluorescent dyes. e.g. sodiu m fluorescein and indocyanine green, the microvascular dynamics, flow distribution and microvascular permeability can also be studied. The t otal skin microcirculation can be evaluated by Laser Doppler fluxmetry , which measures primarily the blood flow in the thermoregulatory vasc ular bed, i.e. the subpapillary arterial and venous plexa. It is easy to use in clinical practice, but interpretation of the results can som etimes be difficult. Measuring transcutaneous oxygen tension has for m any years been used in clinical routine to evaluate the viability of s kin in patients with vascular disorders. It has recently been shown th at inhalation of oxygen may induce vasoconstriction in healthy subject s and in patients with moderate arterial insufficiency, but an increas e of the skin microcirculation in areas of severe ischaemia. By using different combinations of the above mentioned microcirculatory techniq ues, valuable information can be gained regarding pathophysiological p henomena of the microcirculation in many diseases, e.g. vascular disor ders, collagenosis. Raynaud's phenomenon, diabetes and hypertension. U sing techniques for both macro- and microcirculation is also of great importance for evaluating the effect of therapeutic procedures in seve ral of these disorders.