This is an abstract that sucked me in – not because of the concept of the study – but because of its quoted incidence of adverse outcomes. 23.7% incidence of contrast-induced nephropathy following a CT pulmonary angiogram! 12.5% incidence of renal failure! 12.8% in-hospital mortality!
The study itself is a comparison between three different prophylaxis methods for the prevention of CIN after CTPA – N-acetylcysteine plus normal saline, bicarbonate plus NS, or NS alone. The simple summary: no difference between groups.
But, getting back to those dire numbers – roughly double the typically reported incidence of CIN. They’re a mirage. In reality, they assigned the primary outcome to all 26 (9.3%) of patients lost to follow-up. Therefore, the starting point for their outcomes of interest are in a more reasonable range: 15.2% CIN, 2.6% renal failure, and 3.0% in-hospital mortality.
This, again, leads us back to the question: how much renal impairment is attributable to the CTPA, and how much to the underlying disease processes leading patients to require a CTPA in the first place? Yield for PE on their CTPA cohort was 31.9%, which, in itself, elevates the comorbid burden of the population and could contribute to heart failure and renal injury. There is no control group not receiving CTPA – for obvious clinical reasons – so it is hard to estimate the additive injury resulting directly from the CTPA.
But, at least, the big numbers displayed in their abstract a little misleading.
“The high risk of contrast induced nephropathy in patients with suspected pulmonary embolism despite three different prophylaxis: A randomized controlled trial”