IV 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 IV 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, IV 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.