Microvascular function in the peripheral vascular bed during ischaemia and 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 University Department of Vascular Surgery and Institute of Medical Physiology. MATERIALS AND METHODS Ten isolated cat gastrocnemius muscles were perfused with oxygen-free Ringer-albumin solution through the femoral artery. At 5 microliters bolus with 14.8 MBq 51Cr-EDTA was injected through a side branch into the femoral artery, and the response function was detected over the muscle by a scintillation detector connected to a spectrometer and a computer. The perfusion coefficient was measured directly at the venous outlet. The response function was analysed in accordance with non-compartmental black box kinetic principles to give perfusion rate, capillary extraction fraction and capillary diffusional permeability-surface area product (PdS). In separate experiments the molecular size and the free diffusion coefficient of 51Cr-EDTA in water at 37 degrees C were determined by a modified true transient diffusion method. MAIN RESULTS During perfusion the PdS-product increased as a function 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 conductance was identical to that found previously in a similar experimental set up with oxygenated whole blood perfusion. During oxygen free perfusion the perfusion rate was a linear function of arterial perfusion pressure, and autoregulation of blood flow did not occur in response to variations of arterial perfusion pressures. The free diffusion coefficient in water at 37 degrees C for 51Cr-EDTA was 7.4 x 10(-6) cm2/s (n = 36), which corresponds to a Stokes-Einstein molecular radius, rSE, of 0.439 nm. CONCLUSIONS In spite of complete anoxia and absence of normal 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 absence of oxygen under these conditions.