The use of coloured dye-extraction microspheres to measure blood flow in rabbit skeletal muscle: a validation study with special emphasis on repeated measurements.

We evaluated the use of coloured dye-extraction microspheres for measuring blood flow in the skeletal muscle of anaesthetized rabbits. Spheres were injected into the left atrium after sternotomy or lateral thoracotomy, or into the left ventricle via the left carotid artery. Both routes of administration produced adequate mixing of microspheres with the blood. In general, the values of flow obtained from spheres of different colour were well correlated. Resting flows were difficult to measure, owing to the low number of spheres and the correspondingly low absorption of the samples. Occlusion of the capillary bed by trapped spheres was less than 10% in both tibialis anterior and extensor digitorum longus muscles after injection of a total of 15 x 10(6) spheres. Injection via the left ventricle, a closed-chest procedure, gave a more stable preparation than injections via the left atrium. However, in both cases there was a progressive decline in hyperaemic muscle blood flow during a series of injections. These results indicate that it is possible to use this technique to measure skeletal muscle blood flow in the rabbit, but that it is difficult to exploit the advantages of sequential microsphere injection in this species.