AIR-FILLED ULTRASOUND CONTRAST AGENTS DO NOT DAMAGE THE CEREBRAL MICROVASCULATURE OR BRAIN-TISSUE IN RATS

RATIONALE AND OBJECTIVES. Air microemboli may damage the cerebral micr ovasculature. The aim of this study was to evaluate the safety of ultr asound contrast agents composed of air microspheres with regard to cer ebral damage when administered into the arterial system (ie, when not filtered by the capillary system of the lungs). METHODS. Three experim ental methods were used in 75 rats after injection of either Albunex, Echovist, or Levovist into the left heart ventricle, The alkaline phos phatase (ALP) method to demonstrate small segmental brain capillary an d arteriolar dilatations (SCADs), intravenous injections of Evans blue and fluorescence microscopy to detect increased vascular permeability (blood-brain barrier damage), and histologic examination of the brain to detect microinfarction, Intracardiac injections of saline, air, an d corn oil were used as controls. RESULTS. Blain microinfarcts and SCA Ds formation of the brain microvasculature occurred only after control injections with corn oil, None of the brains from animals that receiv ed ultrasound contrast agent showed gross discoloration, as an indicat ion of increased vascular permeability, with the Evans blue/fluorescen ce microscopy method, Definite leakage of Evans blue occurred only aft er large doses (150 mu L) of air. CONCLUSIONS. This study indicates th at ultrasound contrast media composed of air microspheres do not cause lesions of the brain microvasculature or parenchyma.