Hypoperfusion in the Renal outer Medulla after Injection of Contrast Media in Rats

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Abstract
Purpose: the effect on regional renal blood was studied after injection of nonionic iso-osmolar iotrolan or ionic high-osmolar iothalamate. Material and Methods: Laser-Doppler flowmetry was used to measure outer medullary (OMBF) and superficial cortical blood flow (CBF) simultaneously in anesthetized rats. Iotrolan (320 mOsm/kg H2O) was injected i.v. at a dose of 600 mg I/kg b.w. (normal dose) over 2 min or 1,600 (high dose) mg I/kg b.w. over 2 or 8 min. Iothalamate (2,580 mOsm/kg H2O) was injected i.v. at a dose of 1,600 (high dose) or 2,900 (extremely high dose) mg I/kg b.w. over 2 min. Results: At the normal dose and 2-min injection of iotrolan, OMBF was reduced by 25±9% over 20 min. the high dose of iotrolan injected over 8 min resulted in a reduction in OMBF slightly smaller (17±9%) than that induced by the normal dose but lasting longer (30 min). Compared to the normal dose, the high dose and fast (2 min) injection of iotrolan resulted in a greater and more prolonged decrease in OMBF (32±6% lasting 50 min). After the high dose of iothalamate (1,600 mg I/kg) there was a decrease in OMBF by 21±6%, lasting 30 min. An extremely high dose (2,900 mg I/kg b.w.) gave a heterogeneous response with a mean increase in OMBF of 48 ±24% occurring 60 min after the injection. Conclusion: Iso-osmolar and high-osmolar contrast media (CM), at normal and high doses, decrease OMBF, while an extremely high dose of iothalamate may result in an increase. the depression of outer medullary perfusion may have implications for CM-induced acute renal failure in view of the vulnerability of this region to a decrease in oxygen tension.

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