Increasing urine output should reduce the risk for contrast nephropathy, as should hustling contrast metal past vulnerable Na-K-Cl transporters using loop diuretics. However, furosemide alone increases the risk for contrast nephropathy. Some hypothesized that was due to diuretic-induced hypovolemia.
Briguori et al report results of REMEDIAL-II. They randomized ~300 patients at very high risk for contrast nephropathy (half with GFR <30 mL/min, half with GFR <60 mL/min and multiple risk factors) to get either IV acetylcysteine and sodium bicarbonate, or saline and IV acetylcysteine plus the RenalGuard system.
The RenalGuard system is a clever device that monitors urine output and gives saline and furosemide in precise amounts to maintain urine output and fluid balance. It's not approved in the U.S., but in Europe, the company charges ~$500 per use.
Use of this expensive high-tech system did improve renal function according to the very conservative 1' endpoint -- a 0.3 mg/dL increase in creatinine. Only 11% (16 of 146) RenalGuard patients had this outcome, vs. 30 of 146 (20.5%) in the IV NaHCO3/NAC group. More significantly, the intervention group had a strong trend toward a lower need for dialysis while in-hospital (4.1% vs. 0.7%, p=0.056).
Briguori C et al. Renal Insufficiency After Contrast Media Administration Trial II (REMEDIAL II). Circulation 2011;124:1260-1269.
In this same issue, other authors showed that oral N-acetylcysteine alone is ineffective in reducing the risk for contrast-induced acute kidney injury (the ACT trial)