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I.v. N-acetylcysteine and emergency CT: use of serum creatinine and cystatin C as markers of radiocontrast nephrotoxicity.

OBJECTIVE
The purpose of this study was to assess the effect of i.v. administration of N-acetylcysteine (NAC) on serum levels of creatinine and cystatin C, two markers of renal function, in patients with renal insufficiency who undergo emergency contrast-enhanced CT.


SUBJECTS AND METHODS
Eighty-seven adult patients with renal insufficiency who underwent emergency CT were randomized to two groups. In the first group, in addition to hydration, patients received a 900-mg injection of NAC 1 hour before and another immediately after injection of iodine contrast medium. Patients in the second group received hydration only. Serum levels of creatinine and cystatin C were measured at admission and on days 2 and 4 after CT. Nephrotoxicity was defined as a 25% or greater increase in serum creatinine or cystatin C concentration from baseline value.


RESULTS
A 25% or greater increase in serum creatinine concentration was found in nine (21%) of 43 patients in the control group and in two (5%) of 44 patients in the NAC group (p = 0.026). A 25% or greater increase in serum cystatin C concentration was found in nine (22%) of 40 patients in the control group and in seven (17%) of 41 patients in the NAC group (p = 0.59).


CONCLUSION
On the basis of serum creatinine concentration only, i.v. administration of NAC appears protective against the nephrotoxicity of contrast medium. No effect is found when serum cystatin C concentration is used to assess renal function. The effect of NAC on serum creatinine level remains unclear and may not be related to a renoprotective action.