Punching Holes in CIN

Contrast-induced nephropathy, the scourge of modern medical imaging. Is there any way to prevent it? Most trials usually show alternative treatments are no different than saline – but what about saline itself?  Does saline even help?

This most recent publication in The Lancet claims: no. This is AMACING, a randomized, controlled trial of saline administration versus usual care in patients undergoing contrast CT. These authors recruited patients “at risk” for CIN (glomerular filtration rate 30-59 mL per min/1.73m2), and those assigned to the IV hydration arm received ~25 mL/kg over either 8 or 24 hours spanning the timeframe of the imaging procedure. Their primary outcome was incidence of CIN, as measured by an increase in serum creatinine by 25% or 44 µmol/L within 2-6 days of contrast exposure.

Regardless, despite hydration, the same exact number of patients – 8 – in each group suffered downstream CIN. This gives an absolute between groups difference of -0.1%, and a 95% CI -2.25 to 2.06. This is still technically below their threshold of non-inferiority of 2.1%, but, as the accompanying editorial rightly critiques, it still allows for a potentially meaningful difference. Secondary outcomes measured included adverse events and costs, with no reliable difference in adverse events and obvious advantages in the non-treatment group with regards to costs.

This work, despite its statistical power limitations, fits in nicely with all the other work failing to find effective preventive treatment for CIN – sodium bicarbonate, acetylcysteine, et al. Then, it may also tie into the recent publications having difficulty finding an association between IV contrast and acute kidney injury. Do these preventive treatments fail because they are ineffective, or does the clinical entity and its suspected underlying mechanism not exist?  It appears a more and more reasonable hypothesis the AKI witnessed after these small doses of IV contrast may, in fact, be related to the comorbid illness necessitating imaging, and not the imaging itself.

“Prophylactic hydration to protect renal function from intravascular iodinated contrast material in patients at high risk of contrast-induced nephropathy (AMACING): a prospective, randomised, phase 3, controlled, open-label, non-inferiority trial”