Contrast medium dose-to-GFR ratio:: A measure of systemic exposure to predict contrast-induced nephropathy after percutaneous coronary intervention

Background: The contrast medium (CM) dose-to-eGFR (estimated glomerular filtration rate) ratio has recently been advocated to express systemic exposure to CM in assessing the risk of contrast medium-induced nephropathy (CIN). Purpose: To evaluate how CIN risk might vary with decreasing eGFR at fixed CM-dose/eGFR ratios and other CIN risk factors, and to find a relatively safe CM-dose/eGFR ratio. Material and Methods: 391 patients underwent primary coronary angioplasty for ST-segment elevation acute myocardial infarction. CM dose (grams iodine; g I), eGFR (ml/min), and preprocedural CIN risk factors were entered into a multiple logistic regression model. From the established statistical model, the probability of CIN (>= 44.2 mu mol/1 serum creatinine rise or oliguria/anuria) was calculated at various eGFR levels based on g-I/eGFR ratios of 1: 2, 1: 1, 2: 1, and 3: 1. Results: At a g-I/eGFR ratio <1 the risk of CIN was 3%, while it was 25% at a g-I/eGFR ratio >= 1. Independent predictors of CIN were CM dose, eGFR, left ventricular ejection fraction (LVEF) and cardiogenic shock (ROC area=0.87). An estimated CIN risk of 10% would for example occur at a g-I/eGFR ratio of 1.5:1 in patients with 50% LVEF without shock. At a 1: 2, 1: 1, 2: 1, and 3: 1 g-I/eGFR ratio with 50% LVEF without shock, the CIN risk was about 2, 6, 18, and 30%, respectively, over a wide range of eGFR values (30-90 ml/min). At a 1: 1 g-I/eGFR ratio with 50% LVEF + shock, 25% LVEF without shock, or 25% LVEF + shock, the CIN risk was 20, 55, and 80%, respectively. Conclusion: Relating CM dose to eGFR appears to be an attractive pharmacotoxic model to assess CIN risk. At fixed CM-dose/eGFR ratios, CIN risk increased marginally with decreasing eGFR. Limiting the CM dose in g I numerically to the eGFR value in ml/min or less may be relatively safe with regard to CIN, unless multiple risk factors are present.