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  • EDITORIAL: Commentary on CIN

    Contrast-induced nephropathy has gained increasing attention with the revolution in percutaneous interventional procedures. The incidence of CIN varies between studies ranging from 0.6% to 3% though has been noted in up to 50% depending on baseline renal function and the presence of diabetes. Despite extensive studies, the exact mechanism remains poorly understood though related to vasoconstriction, and a reduction in renal blood flow with stasis of contrast causing direct tubular injury up to tubular necrosis. These actions are mediated by endothelins, adenosine & angiotensin II, chronic undiagnosed kidney disease and periprocedural insults also play a role such as renal emboli, transient hypotension, or decreased hematocrit. Despite decades, long attempts at minimizing the renal effects of contrast agents via multiple mechanisms, no singular agent or modality has been proven effective apart from adequate hydration pre as well as post-procedure, even routine hemofiltration or hemodialysis have not been proven effective in patients with chronic kidney disease again illustrating the futility of current modalities. Regarding prognosis, most available data relates to the short and intermediate term effects of contrast nephropathy with relatively little data regarding the long term effects. Battinor et al. in this paper enhance the available literature with data on a large group of patients from the VA Hospital system with follow-up to 5 years [1]. In their study, the authors compared the outcome of 2 groups of patients; those receiving routine pre-procedural IV fluids vs no IV fluids. They found a significant advantage for routine IV fluid administration at 72 h (6.3% vs 9.8%, p = .004) regarding progressive increase in renal function; however, this became nonsignificant by 3 months and showed no impact on the incidence of dialysis or all-cause mortality at 5 year follow-up. Although seemingly disappointing, and before rushing to enumerate all the potential confounding limitations inherent in such a large and complex study, perhaps, it may be prudent to stop and re-evaluate the direction of current research that has recently been more focused on decreasing the dye load up to the recent reports of Zero dye PCI utilizing IVUS & OCT Co-registration which have been proven valuable for selected ultra-high risk patients while perhaps the vast majority may be better served by identifying novel biomarkers with the ability for early identification of patients with seemingly “normal” laboratory values for renal function [2]. The current Achilles heel of these patients is that abnormalities in serum creatinine do not often appear before 1–3 days with the physician basically just waiting & praying that their patient will do well. Such laboratory abnormalities depend on multiple factors beyond the control of the physician such as age, gender, BMI and basal glomerular filtration rate. Moreover, creatinine secreted in urine is not solely a result of glomerular function but also a result of renal secretion and therefore, the rise in serum creatinine will often underestimate the true fall in glomerular filtration rate [3]. By the time serum creatinine peaks post a percutaneous intervention, often there is actually a more than 50% impairment of renal glomerular function, this leads to a delay in diagnosis and proper management which is critical in the early period [4]. Moreover, Kooiman et al. reported on the risk of AKI in 92,317 PCI patients in Michigan & found that the risk of the contrast dose on in-hospital mortality was actually quite weak, only a 1.19 increase in risk casting further doubts on the true value of our attempts at minimizing dye loads. On the bright side & providing light at the end of the tunnel, recent data has shown that Neutrophil Gelatinase Associated Lipocalin (NGAL) is a novel biomarker detectable as early as 2 h in response to kidney injury via a point of care assay available in 35 min with an AUC of 0.95, sensitivity of 0.82 and specificity of 0.90 for prediction of AKI with the potential for early diagnosis & management in the critical period providing the clinician with guidance and resolve [5]. Finally, perhaps now, we can drive while perhaps not so blind!

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