Cath Lab Digest - January 2008 - (Page 8)

8 CLINICAL UPDATE JANUARY 2008 continued from page 1 Contrast Media Use helps to identify patients at risk (Figure 1), but if someone comes in with an acute MI, it’s difficult to fill in all of the integers, because you don’t know their baseline creatinine and their creatinine clearances, and they are just going directly into the cath lab. A paper was published by Dr. Bartorelli’s group in Italy, where they gave the patient intravenous doses of N-acetylcysteine in acute MI (1200 mg IV bolus). They administered it twice daily and those patients actually did quite well,1 but it’s a small study. In an acute MI setting, the most important thing is to assume that everyone is at risk for CIN. Try to limit patient contrast media exposure. Be very judicious about treating patients; really, that should hold for every case. We should be trying to give as little contrast media as possible to our patients. In addition, we need to keep patients as well-hydrated as they can stand both during and after the procedure, because hydration is the one element that we know helps these patients. What is the difference between lowosmolar and iso-osmolar contrast media? Contrast media can be difficult to understand. The compounds have multiple characteristics and one important characteristic is the osmolality. The label “low-osmolar” leads many to assume it must be the lowest osmolality, but in fact “iso-osmolar” media are the lowest osmolality. High-osmolar compounds, with an osmolality over 1200, like HiPeg, no longer even exist. Most of our contrast media are actually low-osmolar compounds, but they are still at twice the osmolality of the iso-osmolar compound. The single iso-osmolar agent we have is Visipaque (iodixanol). It is iso-osmolar to blood, about 297 or 300 milliosmoles. Differences between contrast media Figure 1. Scheme to define contrast-induced nephropathy (CIN) risk score. Anemia = baseline hematocrit value <39% for men and <36% for women; CHF = congestive heart failure class III/IV by New York Heart Association classification and/or history of pulmonary edema; eGFR = estimated glomerular filtration rate; hypotension = systolic blood pressure 1.5 ng/dl. are also attributable to their chemical properties. Compounds are differentiated by ionicity and whether they are monometer or dimer, which has to do with the number of benzene rings. Ionicity is related to the carboxyl group. So, it is not just osmolality that differentiates a certain contrast media. Viscosity (thickness) is another important quality that is not widely discussed. Ultimately, when studying contrast media, one needs to take into consideration all of these qualities, not just the osmolality. How does the viscosity of a contrast agent affect the body? 1. H. Madyoon, P Teirstein, D. Baim, L. Croushore, E. Anderson, V. Mathur. Differential Effects . The most viscous compound available Between Intravenous and Local Renal Delivery of Fenoldopam on Renal Function and Blood is the iso-osmolar non-ionic agent, which Pressure: A Randomized, Controlled Trial. Am J Cardiol September 30, 2004; TCT-51 (Abstract). is iodixanol. That agent, while having the 2. Madyoon H. Clinical Experience with the use of fenoldopam for prevention of radiocontrast nephropathy in high-risk patients. Rev Cardiovasc Med 2001;2(suppl 1):526-530. lowest osmolality, has the highest viscosity. There have been some studies that Adapted from: have shown that viscosity may be actualMinarsch, L. Renal Protection in the Cath Lab: A Novel Therapeutic Device for High-risk Patients Undergoing PCI. Cath Lab Digest Mar 2005;13(3):70-71. ly more detrimental to the kidneys than osmolality. In the Cardiac Angiography Kern M. Contrast-Induced Nephropathy in the Cardiac Cath Lab. Cath Lab Digest April in Renally Impaired Patients (CARE) 2006;14(4):4. trial, which compared low-osmolar contrast agents iopamidol (Isovue) and ioxaglate Table 1. Contrast Media in the Cath Lab (Hexabrix) with iodixanol (Visipaque) in Generic name Osmolality Level Viscosity (cP†) Ionic/ 414 high-risk patients (mOsm/kg H2O*) Non-Ionic undergoing angiograHexabrix 320 ioxaglate Low-osmolar (580) 8.9 at 37°C Ionic phy, there was actually (Guerbet) a trend toward a beneIsovue 370 iopamidol Low-osmolar (796) 9.4 at 37°C Non-Ionic (Bracco Diagnostics) fit for the low-osmolar Visipaque 320 iodixanol Iso-osmolar (290) 11.8 at 37°C Non-Ionic compound as opposed (GE Healthcare) to (iso-osmolar) iodixanol. In fact, in dia* 290 mOsm/kg H2O is the osmolality of blood. † betic patients, that Centipoise. The viscosity of water at 37°C is 0.6915 cP. References trend was even stronger. So I think viscosity does make a difference. Having said that, we also need to consider that iodixanol has been studied in the Contrast Media Utilization in High Risk PTCA (COURT) trial, in close to a thousand patients. Investigators looked at ischemic components and major adverse cardiac events (MACE), which is actually a very strange endpoint — a mishmosh and the kitchen sink, I call it, since MACE is not really just death, MI and revascularization, but a lot of other things. The data showed that iodixanol was better for that major composite endpoint in large numbers of patients. However, this trial did not look at CIN. It was published in 2000 and there was not the focus on contrast nephropathy at that time. How should the CARE trial affect clinical practice? We have a major problem on our hands, which is that right now, in the American College of Cardiology (ACC)/American Heart Association (AHA) guidelines for acute coronary syndromes, we are told to use Visipaque (iodixanol) for PCI. Having this specific recommendation, when clinicians are very much guideline-oriented these days, means that the CARE trial results may not be properly integrated into actual practice. The CARE trial now gives us a large enough data set to say that perhaps the clinical difference between the isoosmolar and the low-osmolar agents

Table of Contents Feed for the Digital Edition of Cath Lab Digest - January 2008

Cath Lab Digest - January 2008 Central Baptist Hospital Contrast Media Use in High-Risk Patients An Ergonomic Survey of Cath Lab Repetitive Stress Injuries Contents Clinical Editor’s Corner Takotsubo Cardiomyopathy, a.k.a., Transient Left Ventricular Apical Ballooning Syndrome: An Acute Coronary Syndrome Imposter Searching for the Key to D2B STEMI Intervention News STEMI Interventions: Commentary The Massachusetts Stent Study The Value of Educating Staff Ask the Clinical Instructor: A Q&A Column for Those New to the Cath Lab SICP* Chapter Updates The Society of Invasive Cardiovascular Professionals Holds an RCIS Review Course at New Cardiovascular Horizons 18:20 To Denver — One Student’s First Clinical Experience CEU Education Center Meetings Calendar What Do You Think? Clinical & Industry News Classifieds The Ten-Minute Interview with…Heather Vardon, RN Advertisers Index

Cath Lab Digest - January 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.