A Micropuncture Assessment of the Effects of Contrast Media of Different Osmolality

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The pathophysiology of radiographic contrast media-induced acute renal failure is unclear. Different causes are suggested, including hypertonicity, charged molecules, and toxicity of the media. This study deals with hemodynamic changes after injection of contrast media of high osmolarity iohexol, and metrizoate. Proximal tubular free-flow and stop-flow pressure (Psf), (the latter a marker of glomerular capillary pressure) were measured before, during, and after injection of contrast media into the renal artery, compared with saline injection, in both normal rats and rats with ureteral obstruction (UO). Urine and electrolyte excretion also were examined. Metrizoate caused an initial decrease in Psf from 37 to 20 mm Hg, followed by an increase to 81 mm Hg, and the value remained high for 10 minutes. During UO, the elevation of Psf was prolonged. Iohexol injection had a less marked effect. The change in glomerular capillary pressure may be dependent on the osmolarity of the contrast agent.

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