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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?
question15. Can we pretreat patients who have borderline renal function? If yes then how?
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?
question 18. What kind of IV access is ideal for use for IV contrast injection?
questionThe best site for IV access is the right antecubital fossa. This site provides a combination of optimal safety plus a good point to time delivery of contrast in studies such as cardiac CTA and pulmonary embolism studies. The left antecubital fossa would be our second choice.

We prefer an 18g angiocatheter in the antecubital fossa when possible. This typically can easily accept injection rates of 5 cc/sec without any problem. We will use a 20g when an 18g is not possible. For 20g we can inject up to 4 cc/sec safely.


"Although 22-gauge catheters may be able to tolerate flow rates up to 5 ml/sec, a 20-gauge or larger catheter is preferable for flow rates of 3 ml/sec or higher. An antecubital or large forearm vein is the preferred venous access site for power injection. If a more peripheral (e.g., hand or wrist) venipuncture site is used, a flow rate of no greater than 1.5 ml/sec may be more appropriate."

ACR Manual on Contrast Media
Version 9 (2013)


"A critical step in preventing significant extravasation is direct monitoring of the venipuncture site by palpation during the initial portion of the contrast medium injection. If no problem is encountered during the first 15 seconds, the individual monitoring the injection exits the CT scan room before the scanning begins. If extravasation is detected, the injection is stopped immediately. Communication between the technologist and the patient via an intercom or television system should be maintained throughout the examination."

ACR Manual on Contrast Media
Version 9 (2013)

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?

 

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