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Everything you need to know about Computed Tomography (CT) & CT Scanning


IV Contrast

question1. Why do we use IV contrast material?
question2. Do you use serum creatinine levels or GFR in your practice for establishing risk prior to CT scanning?
question3. What is GFR and why is it a more accurate measure than simply getting a creatinine level?
question4. Why are GFR numbers different for Caucasians and African Americans?
question5. Are all CT scans with IV contrast done the same way?
question6. What type of IV contrast material do we use and why?
question7. At what temperature do we store IV contrast material?
question8. Why do you warm IV contrast?
question9. What is the advantage of Visipaque as written in the literature?
question10. When do you use Visipaque-320 and when Omnipaque-350?
question11. Does the concentration of contrast mean that higher concentrations are better (AKA-isn’t a higher number better)?
question12. What is the volume of IV contrast material we use?
question13. What patients are considered high risk patients for IV contrast for CIN?
question14. Do we have set cutoffs for creatinine levels and if so what are they?
question 15. Can we pretreat patients who have borderline renal function? If yes then how?
question

Two common regimens are the use of bicarbonate in solution as part of a prestudy ( and often post study protocol) hydration protocol

Use of N-Acetylcysteine (meta-analysis showed no advantage although recent article was more positive about its use)


Prevention Strategies
  • Hydrate to a target urine output of 150 mL/h in the 6 hours postprocedure
  • Avoid nephrotoxic drugs
  • Use prophylactic pharmacologic agents or procedures (eg, NAC, statins, ascorbic acid, hemofiltration)?
  • Minimize volume of CM
  • Consider choice of CM

 


IV contrast chart- bicarbonate


Recent literature has questioned the role of iodinated contrast in being the single factor for CIN (Contrast Induced Nephropathy). Recent articles suggest that creatinine levels will commonly vary even without IV contrast being used and perhaps we are actually doing harm by not using contrast in many patients. This will sort out over time but we are a bit more relaxed these days in giving IV iodinated contrast to patients with creatinines in the 1.8-2.3 range. Here are some articles looking at this subject.


"Intravenously administered low-osmolality iodinated contrast material is independent risk factor for post CT acute renal injury (AKI). Risk increases with increases in pre-CT SCr."

Contrast Material-induced Nephrotoxicity and Intravenous Low-Osmolality Iodinated Contrast Material
Davenport MS et al.
Radiology 2013; 267:94-105


"However, there are many other factors that contribute to the development of post-CT AKI, and not all cases of post-CT AKI are due to CIN. These factors likely account for the equivalence in post-CT AKI rates after unenhanced and contrast enhanced CT shown in recent reports."

Contrast Material-induced Nephrotoxicity and Intravenous Low-Osmolality Iodinated Contrast Material
Davenport MS et al.
Radiology 2013; 267:94-105


"Counterfactual analysis of a large subset of patients who underwent both a contrast enhanced and unenhanced CT scan demonstrates an equivalent likelihood of AKI after either scan."

Intravenous Contrast Material-induced Nephropathy: Causal or Coincident Phenomenon
McDonald RJ et al
Radiology 2013; 267:106-118


"The creatinine level increases in patients who are not receiving contrast material as often as it does in published series of patients who are receiving contrast material. The role of contrast material in nephropathy may have been overestimated."

Frequency of Serum Creatinine Changes in the Absence of Iodinated Contrast Material: Implications for Studies of Contrast Nephrotoxicity
Newhouse JH
AJR 2008; 191:378-382


"Diminished eGFR is associated with an increased risk of SCr-defined AKI following CT examinations. However, the risk of AKI is independent of contrast material exposure, even in patients with eGFR of less than 30 ml/min/1.73m2."

Risk of Intravenous Contrast-mediated Acute Kidney Injury: A Propensity Score-matched Study Stratified by Baseline-estimated Glomerular Filtration Rate
McDonald JS et al.
Radiology 2014;271:65-73


"Contrast material induced nephropathy cannot be differentiated from contrast material dependent causes of AKI, in a predominately inpatient cohort, even in patients with severely compromised renal function."

Risk of Intravenous Contrast-mediated Acute Kidney Injury: A Propensity Score-matched Study Stratified by Baseline-estimated Glomerular Filtration Rate
McDonald JS et al.
Radiology 2014;271:65-73


"Intravenous contrast material administration was not associated with excess risk of AKI acute kidney injury , dialysis, or death, even among patients with comorbidities reported to predispose them to nephrotoxicity."

Intravenous contrast material exposure is not an independent risk factor for dialysis or mortality.
McDonald RJ et al.
Radiology. 2014 Dec;273(3):714-25


"Although patients who developed AKI acute kidney injury had higher rates of dialysis and mortality, contrast material exposure was not an independent risk factor for either outcome for dialysis ( OR odds ratio , 0.89; 95% CI confidence interval : 0.40, 2.01; P = .78) or for mortality ( HR hazard ratio , 1.03; 95% CI confidence interval : 0.82, 1.32; P = .63), even among patients with compromised renal function or predisposing comorbidities."

Intravenous contrast material exposure is not an independent risk factor for dialysis or mortality.
McDonald RJ et al.
Radiology. 2014 Dec;273(3):714-25

question16. Should patients be NPO for CT scanning? If yes for how long?
question17. What are the common volumes of contrast used for IV injection?
question18. What kind of IV access is ideal for use for IV contrast injection?
question19. Has there been any new developments in technology that may help us high injection rates in patients who can not tolerate an 18g needle (or at times even a 20g)?
question20. Can any IV the patient has in place be used to inject the contrast material?
question21. Can we use a central line or a PICC line for injection?
question22. What about the new “purple PICC/central lines” I hear about?
question23. What are some of the common normal “side effects” of IV contrast agents?
question24. Is there a relationship between patients receiving chemotherapy and CIN?
question25. Is it ok for patients to have both an MR and a CT with contrast on the same day?
question26. Have you ever seen a patient develop diffuse erythema distal to the IV injection site in the absence of extravasation?
question27. Patients often report a metallic taste in their mouth following use of IV iodinated contrast. Is there an explanation?
question28. Are there any contrast volume limitations for the use of IV contrast?
question29. Can you tell me a bit more about GFR and what it really means?

 

© 1999-2021 Elliot K. Fishman, MD, FACR. All rights reserved.