Preventing Contrast Induced Nephropathy

Preventing Contrast Induced Nephropathy

Michael Smith

Overview
Contrast induced nephropathy (CIN) is a serious concern for today’s emergency physician when ordering contrast enhanced imaging. CIN is usually defined by an increase in serum creatinine by 0.5 mg/dL or 25% from baseline that usually occurs 2-3 days after contrast administration.[1] The incidence of CIN is estimated to be 1-2% in the general population, but the relative risk is greatly increased in diabetics, the elderly, and those with intrinsic renal disease, congestive heart failure, and dehydration.[1,2] It is the duty of the emergency physician ordering the study to assess risk of developing CIN, as other care providers may not adequately identify patients at risk.[3] Careful selection of patients for contrast imaging is paramount especially in this day of frequent and profuse imaging of both medical[4] and trauma[5] patients.

Prevention
The first step in preventing CIN is determining if a contrast enhanced study is actually clinically indicated. For example, a reasonable starting point might be to employ judicious use of CT scans in trauma patients, a group in whom contrast-enhanced CT scanning is routinely ordered and whole body scanning has become rampant.[6] Screening with ultrasonography may facilitate a decrease in CT scans in both medical and trauma patients. Finally, contrast administration may prove unnecessary for certain patients. For instance, data indicates that the lack of contrast does not alter the sensitivity of an abdominal CT for appendicitis.[7]

Once it has been determined that contrast enhanced imaging is clinically indicated, a few preventative measures can be initiated. Sodium chloride hydration remains the mainstay of choice for CIN prevention.[8] Studies have also demonstrated benefit to administering sodium bicarbonate for preventing CIN.[9] Controversy remains regarding the minimal benefit of adding n-acetylcysteine (N-AC) to the treatment regimen.[10] The use of both theophylline and high dose ascorbic acid has been proposed, but no methodologically or statistically sound studies exist, making the measurement of efficacy of ascorbic acid and theophylline in preventing CIN uncertain. Unfortunately, the majority of studies address CIN induced as a result of coronary angiography. There is some thought that ED CT contrast might be slightly safer than angiography contrast, but we are only able to extrapolate based on the available data.

Application to Emergency Medicine
Prevention of contrast induced nephropathy remains as a significant challenge for today’s emergency physician. Sound clinical judgement regarding the actual need of a contrast enhanced study is essential. The responsibility of risk stratification to assess for potential development of CIN remains that of the emergency physician ordering the study. Sodium chloride and sodium bicarbonate hydration, while not risk free, remain fairly safe and reasonably effective means of preventing CIN. The utility of N-AC, ascorbic acid and theophylline is unproven at best. Most studies reflect the incidence and treatment of CIN induced by angiography contrast, rather than CT contrast. However, some extrapolation and application of the above principles may be useful.

References
Pucelikova T, et al: Contrast-induced nephropathy. Catheter Cardiovasc Interv. 2008 Jan 1;71(1):62-72. 17975790
Wong GT, Irvin MG: Contrast-induced Nephropathy. Br J Anaesth. 2007 Oct;99(4):474-83. 17681968
Reddan, D, Fishman, EK: Radiologists' knowledge and perceptions of the impact of contrast-induced nephropathy and its risk factors when performing computed tomography examinations: a survey of European radiologists. Eur J Radiol. 2008 May;66(2):235-45. 17728089
Broder J, et al: Increasing utilization of computed tomography in the pediatric emergency department, 2000-2006. Emerg Radiol. 2007 Sep;14(4):227-32. 17505849
Beck D, et al: Prospective study of the clinical predictors of a positive abdominal computed tomography in blunt trauma patients. J Trauma. 2004 Aug;57(2):296-300. 15345975
Aucar J, et al: If a picture if worth a thousand words, what is a trauma computerized tomography panel worth? Am J Surg. 2007 Dec;194(6):734-9; discussion 739-40.
Tamburrini S: Accute appendicitis: diagnostic value of nonenhanced CT with selective use of contrast in routine clinical settings. Eur Radiol. 2007 Aug;17(8):2055-61. Epub 2006 Dec 16. 17180324
Van Praet J, et al: Prevention of contrast-induced nephropathy: a critical review. Curr Opin Nephrol Hypertens. 2007 Jul;16(4):336-47.
Masuda M: Comparison of usefulness of sodium bicarbonate versus sodium chloride to prevent contrast-induced nephropathy in patients undergoing an emergent coronary procedure. Am J Cardiol. 2007 Sep 1;100(5):781-6. Epub 2007 Jun 13.
Brigouri C: Renal insufficiency following contrast media administration trial (REMEDIAL): a randomized comparison of 3 preventive strategies. Circulation. 2007 Mar 13;115(10):1211-7. Epub 2007 Feb 19. 17309916