This is an observational study assessing the impact of conventional dose iodinated contrast on the renal function of advanced chronic kidney disease patients undergoing arteriovenous fistula evaluation using a standard sodium bicarbonate prophylaxis protocol. In addition, this model allows for pre and post procedure measurements of kidney function, providing a unique opportunity to assess the utility of novel biomarkers for contrast-induced kidney injury.

Our primary hypothesis is that there will be no change in serum creatinine post-procedure when using a standard sodium bicarbonate prophylaxis protocol. Our secondary hypothesis is that there will be no change in urinary kidney-injury marker-1 (KIM-1) post-procedure using a standard sodium bicarbonate prophylaxis protocol. In addition, we will assess the impact of different patient characteristics on the development of contrast-induced kidney injury, such as diabetes, coronary artery disease, hypertension, and angiotensin converting enzyme inhibitor therapy.

The National Kidney Foundation publishes kidney disease outcome guidelines for improving care of the chronic kidney disease (CKD) patient. Regarding hemodialysis vascular access, the recommendation is for early placement of an arteriovenous fistula (AVF) to improve morbidity and mortality outcomes, specifically when the glomerular filtration rate is less than 25ml/min, corresponding to stage 4 and 5 CKD. Despite its advantages, the need for surveillance of the AVF to determine maturation for use and maintain optimal longevity requires the use of interventional procedures. While radiocontrast use can lead to acute, often reversible kidney injury, its use in AVF evaluation has renewed interest with the recent implication of gadolinium-enhanced MRI being associated with a rare disorder of skin swelling and induration called nephrogenic systemic fibrosis. CKD patients are particularly susceptible to long term adverse outcomes from contrast-induced kidney injury, with 1 year mortality in stage 4 and 5 CKD patients being 44% and 62%, respectively. While optimal fluid therapy to prevent contrast-induced kidney injury remains uncertain, several prospective randomized trials using sodium bicarbonate pretreatment have shown a lower incidence of contrast-related kidney injury compared to isotonic saline. Traditional markers of acute kidney injury, including serum creatinine, blood urea nitrogen, and creatinine clearance have been insensitive in differentiating contrast-induced kidney injury from other forms of renal injury. Kidney injury marker-1 (KIM-1) is a transmembrane receptor induced to very high levels in the proximal tubule of the nephron following ischemic and nephrotoxic injury. KIM-1 has been shown in a small cohort of patients to differentiate ischemic kidney injury from other forms of acute and chronic kidney disease.

Inclusion Criteria:

• English speaking
• >18 yrs age
• chronic kidney disease, documented GFR<30ml/min by abbreviated MDRD calculation

Exclusion Criteria:

• Inpatients
• Pediatric patients
• Non-English speaking patients
• established dialysis patients
• patients receiving iodinated contrast within 30 days of current procedure
• patients with central arterial manipulation within 30 days of current procedure

Stage 4 and 5 chronic kidney disease patients with AV fistula placed but have not initiated dialysis.