Determination of Glomerular Filtration Rate with Contrast Media

Prevention of contrast-induced nephropathy by limb ischemic preconditioning: underlying mechanisms and clinical effects

Contrast-induced nephropathy (CIN) is an important complication following diagnostic radiographic imaging and interventional therapy. It results from administration of intravascular iodinated contrast media (CM) and is currently the third most common cause of hospital-acquired acute kidney injury. CIN is associated with increased morbidity, prolonged hospitalization, and higher mortality. Although the importance of CIN is widely appreciated, and its occurrence can be mitigated by the use of pre- and posthydration protocols and low osmolar instead of high osmolar iodine-containing CM, specific prophylactic therapy is lacking. Remote ischemic preconditioning (RIPC), induced through short cycles of ischemia-reperfusion applied to the limb, is an intriguing new strategy that has been shown to reduce myocardial infarction size in patients undergoing emergency percutaneous coronary intervention. Furthermore, multiple proof-of-principle clinical studies have suggested benefit in several other ischemia-reperfusion syndromes, including stroke. Perhaps somewhat surprisingly, RIPC also is emerging as a promising strategy for CIN prevention. In this review, we discuss current clinical and experimental developments regarding the biology of CIN, concentrating on the pathophysiology of CIN, and cellular and molecular mechanisms by which limb ischemic preconditioning may confer renal protection in clinical and experimental models of CIN.

Gadolinium contrast media are more nephrotoxic than a low osmolar iodine medium employing doses with equal X-ray attenuation in renal arteriography: an experimental study in pigs

RATIONALE AND OBJECTIVES

To investigate in a unilaterally nephrectomized porcine model whether gadolinium contrast media (Gd-CM) are less nephrotoxic than iodine media (I-CM) in x-ray arteriography of a kidney made temporarily ischemic by arterial balloon occlusion.

MATERIALS AND METHODS

In a noncrossover design, 3 mL of each test solution were injected in eight pigs (mean weight 19 kg) at a rate of 20 mL/min into the right renal artery at the start of a 10-minute period of ischemia. In group 1 (40 pigs) we injected 0.5 M gadopentetate, 0.5 M gadodiamide, 0.5 M iohexol (190 mg I/mL), 0.18 M iohexol (70 mg I/mL; with an x-ray attenuation equal to that of 0.5 M Gd-CM at 80 kV), and saline. In group 2 (24 pigs), we tested 0.18 M iohexol with ischemia and saline with and without ischemia. Gd- and iodine contrast media functioned as markers of glomerular filtration rate (GFR). When saline was tested, a low dose of iohexol (3 mL per pig; 300 mg I/mL) was injected as GFR marker intravenously in group 1 and into the renal artery in group 2. The plasma half-life elimination times of the CM 1-3 hours after injection were used to compare the effects of the different test solutions on GFR. Longer half-life means lower GFR.

RESULTS

Group 1: median plasma half-life elimination time of the GFR marker was 3 340 minutes after injection of 0.5 M gadopentetate, 256 after 0.5 M gadodiamide, 179 after 0.5 M iohexol, 143 after 0.18 M iohexol, and 133 minutes after saline. All differences except that between 0.18 M iohexol and saline were statistically significant (P < .01). Group 2: median plasma half-life was 174 minutes after 0.18 M iohexol with ischemia, 196 minutes after saline with ischemia, and 195 minutes after saline without ischemia. There were no significant differences between the test solutions in group 2 (P > .05).

CONCLUSION

In pigs, 0.5 M Gd-CM were more nephrotoxic than both equal-attenuating (70 mg I/mL) and equimolar (190 mg I/mL) concentrations of the I-CM iohexol. These results do not support the "off-label" use of Gd-CM for renal x-ray arteriography in man instead of commercially available concentrations of iodine contrast media at 140, 150 and 180 mg I/mL or diluted to 70 mg I/mL.