The intravascular administration of iodinated contrast media for diagnostic imaging is a common cause of acute kidney injury (AKI) and a leading cause of iatrogenic renal disease. Contrast-induced AKI is associated with serious adverse outcomes including death, need for dialysis, prolonged hospitalization, and acceleration in the rate of progression of underlying chronic kidney disease. The benefit of IV isotonic bicarbonate compared to IV isotonic saline and of N-acetylcysteine for the prevention of contrast-induced AKI and associated adverse outcomes remains unclear. The purpose of this trial is to compare the effectiveness of IV isotonic sodium bicarbonate with IV isotonic sodium chloride and oral NAC with placebo for the prevention of serious adverse outcomes in 7,680 high-risk patients scheduled to undergo coronary or non-coronary angiography. Using a 2 x 2 factorial design, patients will be randomized to receive: 1) either peri-procedural IV isotonic sodium bicarbonate or peri-procedural IV isotonic saline and 2) either oral NAC or oral placebo prior to and for 5 days following the angiographic procedure. The primary study endpoint is a composite outcome comprised of death, need for acute dialysis, or persistent decline in kidney function within 90 days following the index angiogram.