Diagnostic imaging matters


different between iodixanol and comparator LOCM in moderate-risk or low-dose procedures41–44


It is also important to realise that markers of renal function such as serum creatinine (SCr) and creatinine clearance (CrCl) may have their highest deviation from baseline any time within 1–7 days (usually 2–3 days) after exposure to contrast media.45


Therefore, SCr should


ideally be measured two or three times after exposure to contrast medium; if repeat samplings are not feasible, all patients should be sampled at a fixed time point. As seen in Tables 1 and 2, some studies used single SCr samplings taken over different time periods up to 72 hours (up to 120 hours in one study). Such random sampling procedures may introduce significant bias, as maximum SCr values may be missed.46


Comparator contrast medium


Contrast medium volume (ml) Iodixanol


Comparator Patients (n) Patients with renal impairment (%)


Patients with diabetes (%) Iodixanol


Comparator


Baseline SCr (µmol/l) Iodixanol


Comparator


Baseline CrCl (ml/min) Iodixanol


Comparator


Follow-up SCr Number Timing


Definition of CIN (change in SCr)


CIN rate (%) Overall


Iodixanol Comparator p value


Nguyen et al40 Iopromide


115 100 117 100


37.7 17.9


156 ± 21.2 155 ± 28.3


51.8 ± 16.6† 53.0 ± 26.0†


3 Day 1, 2, 3 25%


17.7 8.5


27.8 0.012


44.2 µmol/l


11.1 5.1


18.5 0.037 25%


3.9 4.0 3.9 NS


Summary Viscosity has been proposed as a key factor influencing the development of nephrotoxicity, as there is evidence that contrast media with high viscosity result in renal tubular vacuolisation. The preclinical models suggesting an important role for viscosity in renal toxicity involving animals whose renal physiology differs from that of humans in some respects. There is also no clinical evidence that suggests that vacuolisation or differences in renal elimination are associated with nephrotoxicity. Indeed, many studies of contrast media with different viscosities have shown no difference in CIN rates and sometimes a lower rate of CIN in patients receiving the more viscous but lower isosmolar iodixanol, compared with less viscous hyperosmolar contrast media.


IMPACT42 Iopamidol


125* 108* 153 100


27.6 19.5


133 ± 44.2 141 ± 35.4


45.2 ± 11.3 44.1 ± 14.0


1 48–72 hours


44.2 µmol/l


1.3 2.6 0


NS


ACTIVE43 Iomeprol


125* 100* 148 100


12.5 27.6


150.3 ± 61.9 150.3 ± 53.0


43.0+13.3 41.5+13.1


1 48–72 hours


(and day 7 for patients with CIN) 25%


44.2 µmol/l


3.1 6.9 5.3 NS


Table 2: Head-to-head studies of iodixanol versus other contrast media—intravenous administration *Patients were given a prespecified total iodine dose of 40 g, administered at a standardised injection rate of 4 ml/s. †


3.4 6.9 0


0.025


PREDICT44 Iopamidol


101.6 ± 23.7 106.5 ± 25.5 248 100


100 100


124.6 ± 33.6 129.1 ± 38.9


49.9 ± 11.6† 47.6 ± 13.5†


1 48–72 hours 25%


5.2 4.9 5.6 NS


Glomerular filtration rate. IMPACT,


Isovue-370 and Visipaque-320 in Renally Impaired Patients Undergoing Computed Tomography study; ACTIVE, Abdominal Computed Tomography: Iomeron 400 versus Visipaque 320 Enhancement Study; PREDICT, Patients with Renal Impairment and Diabetes Undergoing Computed Tomography study; SCr, serum creatinine; CrCl, creatinine clearance; CIN, contrast-induced nephropathy; NS, not specified. For consistency, the values and units cited here are not always the same as those given in the references, but have been calculated from them.


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