Introduction
The administration of radiocontrast media during a radiology or cardiac diagnostic procedure is known to cause a type of
kidney failure called contrast-induced nephropathy. Although the mechanism of the injury isn’t known for sure, it is thought to be due to constriction of the blood vessels in the kidney and possibly free oxygen radical damage. This type of acute kidney failure begins very soon after the contrast is given and in most causes is in only temporary. Some people, particularly those with bad kidneys to begin with, can end up requiring dialysis (often only temporarily but sometimes permanently).
Risks for Contrast Nephropathy
Most people who get contrast nephropathy have problems with their kidneys before the test or procedure (as demonstrated by an
elevated creatinine) and are often diabetic. The risk factors for contrast nephropathy include:
- Kidney dysfunction with creatinine > 1.5 mg/dL
- Diabetic nephropathy with kidney dysfunction
- Advanced heart failure
- High doses of radiocontrast
- Multiple Myeloma
Preventing Contrast Nephropathy
There has been a lot of interest in this area and a number of studies performed. To date, the best way to prevent contrast nephropathy is:
- Either avoiding or reducing the amount of contrast given
- Using the latest contrast agents (non-ionic and low osmolality)
- Avoiding dehydration (often through given extra fluids)
- Avoiding kidney toxic drugs (such as NSAIDS)
N-Acetylcysteine
In the early 2000’s, a study was published showing that the antioxidant N-Acetylcysteine (often called Mucomyst or Fluimucil) helped prevent contrast nephropathy. Despite the fact that this study was flawed and the actual benefit was probably due to good hydration to prevent dehydration, it generated a lot of interest because of its very low cost, relatively low risk, and potential antioxidant benefits. A number of studies (> 25) have been performed since and the results have been inconclusive. Despite this, it is widely used and interest in it is still intense.
Recent Study Results
The New England Journal of Medicine published an article in their June 29, 2006 issue called “N-Acetylcysteine and Contrast-Induced Nephropathy in
Primary Angioplasty”. They took 354 patients who were having a heart attack and undergoing a cardiac angioplasty and put them into three groups. One third of the people received a standard dose N-Acetylcysteine, one third received a high dose, and the third did not receive it (the control or placebo). They reported that 33% of the control group had acute kidney failure compared to 15% of those getting the standard dose and 8% of those getting the higher dose.
Discussion
Acute kidney failure from contrast nephropathy is a serious problem. Fortunately, for most people, it is only a temporary one and kidney function quickly recovers. For some people, particularly those with heart problems, the consequences can be more serious. This is in part because heart disease (particularly heart failure) can cause kidney problems. There is a lot of interest in N-Acetylcysteine in preventing contrast nephropathy because it is inexpensive, has relatively low risk, and may have other antioxidant benefits. Although this recent study was limited to a group of heart patients who were having a heart attacks and undergoing angioplasty, it will likely be used to justify giving N-Acetylcysteine to all angioplasty patients. I am not entirely convinced that the benefits seen were due the N-Acetylcysteine but given the low cost and relatively low risk, I will recommend its use until there is a reason not to.
Sources
Marenzi et al. "N-Acetylcystine and Contast-Induced Nephropathy in Primary Angioplasty". NEJM 354 (2006): 2773-2782
