Red Cell Factor in Renal Damage from Hypertonic Solutions

Gadolinium contrast media are more nephrotoxic than iodine media. The importance of osmolality in direct renal artery injections

A study was undertaken of the role of osmotoxicity in gadolinium (Gd) and iodine contrast media (CM) nephrotoxicity in ischemic porcine kidneys. Test solutions: mannitol iso-osmotic to 0.5 M: gadopentetate (1.96 Osm/kg H2O), 0.5 M: gadodiamide (0.78 Osm/kg H2O) and 0.5 M: iohexol (190 mg I/ml, 0.42 Osm/kg H2O). Each solution was injected [3 ml/kg body weight (BW)] into the balloon-occluded (10 min) renal artery of eight left-sided nephrectomized pigs. The plasma half-life of a glomerular filtration rate (GFR) marker was used to compare their effects on GFR 1-3 h post-injection. The median half-lives of the GFR marker after injection of gadopentetate (1,730 min) and mannitol 1.96 Osm/kg H2O (2,782 min) did not differ statistically (P = 0.28), but were significantly longer than after all other solutions (P < 0.001). There was no significant difference (P = 0.06) between gadodiamide (218 min) and mannitol 0.82 Osm/kg H2O (169 min), while there was (P = 0.03) between iohexol (181 min) and mannitol 0.43 Osm/kg H2O (148 min). The difference between gadodiamide and iohexol was significant (P = 0.01). Reduction in GFR, as a marker of nephrotoxicity, induced by gadopentetate correlated with its high osmolality, while the effect of gadodiamide and iohexol may include chemotoxicity. Iohexol molecules were less nephrotoxic than the Gd-CM molecules and contain three-times the number of attenuating atoms per molecule.

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.