Route of administration of contrast media

The risk of CI-AKI appears to be greater after arterial compared to venous administration of contrast media. Indeed, in the rare studies where an appropriate control group without contrast media was included, no significant difference was observed in the rate of CI-AKI between the patients who received i.v. iodinated contrast media and the control subjects who did not.440-442 Thus, the risk of CI-AKI with i.v. contrast medium is probably very low. CI-AKI reportedly occurs after i.v. contrast-medium injection for CT in only 4% of patients with CKD.443 Katzberg and Lamba444 summarized the six studies on CI-AKI after i.v. contrastmedium administration in patients at risk and all suffering from moderate CKD. The overall incidence of CI-AKI in these studies, using the current generation of low-osmolar contrast media, was about 5%.

Given the logistic challenges in the outpatient setting, the use of specific prophylactic measures prior to administration of i.v. contrast media could be limited to those subjects who are at higher levels of baseline risk than they would be when an i.a. procedure was planned.445 This conclusion, may

Table 16 | Additional radiological measures to reduce CI-AKI
Some CT strategies in patients at risk of CI-AKI
  • Perform CT, when possible, without contrast media; scrutinize the examination and discuss with the referral physician-surgeon before deciding on the need for contrast media.
  • Dosing per kilogram body weight to reduce the amount of contrast media is needed in thin patients.
  • Adapt injection duration to scan duration when performing CT-angiography, so that the injection is not still running when the scan is finished.
  • Use a saline chaser to decrease the amount of contrast media, by using the contrast medium that otherwise would remain in the dead space of the arm veins; this may save 10–20 ml of contrast media.
  • Use 80 kVp; contrast-medium dose may be reduced by a factor of 1.5–1.7 compared to the dose used at 120 kVp since iodine attenuation increases, and combine with increased tube loading (mAs) to maintain signal-to-noise ratio.
  • Further reduction of contrast media may be instituted in patients with known decreased cardiac output (not unusual in patients with renal impairment) undergoing CT-angiographic studies.
Some angiographic strategies in patients at risk of CI-AKI
  • Use biplane when appropriate.
  • Avoid test injections; the same amount may be enough for a diagnostic digital-subtraction angiography run.
  • Scrutinize each series before performing the next; avoid unnecessary projections.
  • Decrease kilovoltage in a thin patient; a lower iodine concentration may be used.
  • Assess the physiologic significance of a stenosis by measurement of translesional pressure gradient and fractional flow reserve, a technique well accepted and validated for the coronary circulation. For different arterial beds, perform manometry of a questionable stenosis instead of multiple projections.
  • Avoid ventriculography: echocardiography (and ‘‘echo contrast’’) is always a reasonable alternative.
  • Use plasma isotonic contrast-media concentrations for renal artery injections.
  • When renal artery stenosis is suspected, map the origin of major renal arteries with noninvasive procedures (e.g., CT without contrast media) for proper initial renal angiographic projections to avoid unnecessary runs, or perform primary manometry.
  • CO2 may be used as contrast medium in venous examinations and below the diaphragm for arterial examinations or alternatively use iodinated contrast media with the same contrast effect, i.e., about 40mg iodine per milliliter.
  • Since the contrast effect of 0.5M Gd-contrast media has been regarded as diagnostic by many investigators (coronary, renal, aortofemoral arteriography, etc.), iodinated contrast media may be diluted to the same density, i.e., about 75mg iodine per milliliter.
  • Use selective or superselective catheterizations when appropriate, e.g., ‘‘single leg run-off’’.
  • Reduce aortic flow and amount of contrast medium by temporal occlusion of femoral arteries with tourniquets when performing aortography.

Gd, gadolinium; kVp, peak kilovoltage.

however, be too optimistic when applied to critically ill patients undergoing emergency CT scans.395

The majority of the literature covering CI-AKI and its prevention involves i.a. iodinated contrast-medium administration.445,446 The higher risk of CI-AKI after i.a. administration is probably due to the more direct exposure of the kidneys to contrast media,447 or to the fact that, in general, i.a. contrast-media examinations are performed in patients who carry a higher risk.