ABSTRACT
Chronic kidney disease is defined through a range of eGFR values by the National Kidney Foundation Kidney Disease Outcomes Quality Initiative (KDOQI) as depicted in Figure 2.3.7 Most studies of cardiovascular outcomes have found that a breakpoint for the development of CIN, later restenosis, recurrent myocardial infarction (MI), diastolicsystolic congestive heart failure (CHF), and cardiovascular death occurs below an eGFR of 60 mlmin per 1.73 m2, which roughly corresponds to a serum Cr of > 1.5 mgdl in the general population.81-84 Because Cr is a crude indicator of renal function, and often underestimates renal dysfunction in women and the elderly, calculated measures of eGFR or CrCl by the Cockroft-Gault equation or by the MDRD equations, now available on the web, personal digital assistants, and with hand-held plastic estimators are the preferred methods of estimating renal function.The four-variable MDRD equation for estimated GFR is the preferred method since it does not rely on body weight.85 This equation is given below:
GFR = (186.3 × [serum creatinine−1.154] × [age− 0.203])
calculated values are multiplied by 0.742 for women and by 1.21 for African Americans. In addition, microalbuminuria (defined as a random urine albumincreatinine ratio (ACR) of 30-300 mgg) at any level of eGFR is considered to represent CKD, and has been thought
Figure 2.3 The classification of chronic kidney disease according to the National Kidney Foundation Kidney Disease Outcomes Quality Initiative (KDOQI). Increased rates of adverse events are generally seen below an estimated glomerular filtration rate of 60 mlmin per 1.73 m2. CIN: contrast-induced nephropathy; CKD: chronic kidney disease; GFR: glomerular filtration rate; ESRD: end stage renal disease. (From McCullough PA, Sandberg KR7, with permission.)
to occur as the result of endothelial dysfunction in the glomeruli.86 It is critical to understand that the risk of CIN is related in a curvilinear fashion to the eGFR, as shown in Figure 2.4.8
Multivariate prediction scoring schemes have been developed and indicate that patients with multiple risk factors can have a very high, if not certain expectation for the development of CIN after contrast exposure during PCI (Figure 2.5).88 This validated scoring scheme can be used to anticipate CIN before and immediately after coronary angiography. As Figure 2.5 implies, elderly, diabetic patients with reduced eGFR or elevated Cr, with additional risk features, can have CIN and ARF requiring dialysis rates as high as 57 and 16%, respectively. Hence, this type of scheme can be used in the informed consent process, prevention planning, and anticipation of the need for dialysis after the procedure.
