Author + information
- Christopher S.R. Baker, PhD, MRCPa ()
- Atholl Johnston, PhD, MRCPath,
- Laurence R.I. Baker, MD, FRCP and
- Charles J. Knight, MD, MRCP
We understand that intravenous (IV) n-acetylcysteine (NAC) as used in our study (Celltech Pharmaceuticals, Berkshire, SL1 3WE, United Kingdom) is not available in the U.S. We agree with Huxtable and colleagues' concerns over the use of inhalational NAC for the prevention of radiocontrast-induced nephropathy (RCIN), particularly as this preparation requires the use of 5% dextrose as the diluent. Although a saline-induced diuresis appears to be effective in reducing the incidence of RCIN (1)there is no evidence for the efficacy or otherwise of 5% dextrose.
In the absence of a proven IV preparation, the proposal by Huxtable et al. for the use of saline hydration and oral NAC seems eminently sensible although, as they point out, evidence for the effectiveness of oral NAC when given immediately prior to contrast exposure is limited. A variety of other maneuvers may also reduce the incidence of RCIN, and we would suggest the following be included in any protocol:
1. The use of iso-osmolar contrast agents (2).
2. Minimization of the radiocontrast dose employed (3)(e.g., biplane imaging and echocardiography in place of contrast ventriculography).
3. Maximum 4-h fast prior to contrast exposure to prevent salt and water depletion.
4. Cessation of potentially nephrotoxic drugs prior to contrast exposure and reinstitution when renal function has been shown to be stable.
5. Assessment of renal function three days' postprocedure.
We believe that awareness of RCIN will do much to reduce its impact.
The suggestion of a third arm to the study to compare oral and IV NAC is an interesting one. However, this was discounted during the design stage of our trial owing to the low incidence of RCIN in patients treated with oral NAC (approximately 2% ). The estimated number of patients required to show a difference or to prove equivalence between treatments would thus have been prohibitively large.
Finally, we emphasize that our study did not include emergency patients, as this would not have allowed randomization to the slower hydration arm of the protocol.
- American College of Cardiology Foundation