MICROVASCULAR FUNCTION IN THE PERIPHERAL VASCULAR BED DURING ISCHEMIAAND OXYGEN-FREE PERFUSION

Objectives: To determine the influence of acute ischaemia and absence of leukocytes on the microvascular function and capillary permeability in skeletal muscle. Design: Prospective, open study. Setting: Univers ity Department of Vascular Surgery and Institute of Medical Physiology . Materials and Methods: Ten isolated cat gastrocnemius muscles were p erfused with oxygen-free Ringer-albumin solution through the femoral a rtery. A 5 mu l bolus with 14.8 MBq Cr-51-EDTA was injected through a side branch into the femoral artery, and the response function was det ected over the muscle by a scintillation detector connected to a spect rometer and a computer. The perfusion coefficient was measured directl y at the venous outlet. The response function was analysed in accordan ce with non-compartmental black box kinetic principles to give perfusi on rate, capillary extraction fraction and capillary diffusional perme ability-surface area product (PdS). In separate experiments the molecu lar size and the free diffusion coefficient of Cr-51-EDTA in water at 37 degrees C were determined by a modified true transient diffusion me thod. Main Results: During perfusion the PdS-product increased as a fu nction of flow rate, f, in accordance with the linear regression line PdS = 1.78 + 0.15 f between 5 to 60 ml/100 g/min. This permeative cond uctance was identical to that found previously in a similar experiment al set up with oxygenated whole blood perfusion. During oxygen free pe rfusion the perfusion rate was linear function of arterial perfusion p ressure, and autoregulation of blood flow did not occur in response to variations of arterial perfusion pressures. The free diffusion coeffi cient in water at 37 degrees C Cr-51-EDTA was 7.4 X 10(-6)cm(2)/s (n = 36), which corresponds to a Stokes-Einstein molecular radius, r(SE), of 0.439 nm. Conclusions: In spite of complete anoxia and absence of n ormal microcirculatory flow regulating mechanisms there is no sign of changes in capillary diffusional permeability for smaller hydrophilic molecules and functional membrane damage is not elicited in the absenc e of oxygen under these conditions.