Skeletal muscle blood flow in anaesthetized horses. Part I: measurement techniques

Numerous techniques have been used in horses to study skeletal muscle blood flow during anaesthesia and after the administration of vasoactive agents. Of the available techniques, blood flow measurements are limited to either microvascular flow (radioactive xenon, laser Doppler flowmetry) or total blood flow (radioactive microspheres, electromagnetic flowmetry, Doppler ultrasonography). None of the techniques currently available are able to fully assess the distribution of flow throughout the skeletal muscle. Near-infrared spectroscopy has the potential to assess the adequacy of oxygenation within muscles; however, this technique is not without limitations, and more work is required to assess its suitability. Understanding the limitations of these techniques is an important prerequisite to the critical evaluation of the information currently available on the effects of anaesthesia and vasoactive drugs on skeletal muscle blood flow.