Do You Warm CT Contrast?Sep 14, 2021
So, the American College of Radiology (ACR) has looked at this in depth and I’m quoting them verbatim here, directly from the 2021 ACR contrast manual on page 30: “Although there is good evidence that warming of contrast media changes the bolus kinetics and injection pressure of iodinated contrast media, there has been very little evidence that it affects clinical adverse event rates in a meaningful way.”
Well, what does this mean? It means that you don’t have to warm the contrast. I have never worked at an institution that has warmed the contrast before intravenous injection and my personal point of view says that based on the evidence and personal experience, it’s not necessary either. Now, there are some potential benefits to the warming of contrast, which the manual also points out on page 31. They basically conceded that for very high flow rates, greater than 5 mL per second, it could be helpful. As you know, the contrast we inject is pretty thick stuff. Try blasting some into the trash bin using a syringe with a 22 gauge needle and then compare that to blasting normal saline through the same size needle. You will see a significant difference. The idea here on the beneficial side is that by warming the contrast, you are making the thick fluid less viscous and easier to inject. This also theoretically means, that if you are stuck using a small IV, you can still get a higher flow rate. However, none of these reasons in my humble opinion are good enough for me to institute contrast warming at my institution.
So to back up at least some of the claims in the ACR and my personal point of view, there is a new article out in the American Journal of Radiology (here is a direct link), basically saying that contrast warming is unnecessary. Let’s take a quick look at the authors’ results. So the study had almost 4000 patients and the rate of adverse events in this contrast warmed cohort was NOT statistically different from the overall adverse event rate in the non-warmed contrast patients. This included allergic reactions and extravasations. Cool. This makes me feel a whole lot better about deciding not to utilize contrast warming in my hospital or outpatient centers.
However, am I missing something? Am I getting something wrong here? I really don’t think so, but let’s go through a thought experiment. Think about something like maple syrup. Maple syrup is pretty thick stuff, however if you put a small cup of it in the microwave for 15 seconds, it becomes a lot easier to pour. That’s the whole idea behind warming the pretty viscous IV contrast material. You are making the contrast less viscous before injection. And aside from a higher flow rate, an additional theoretical advantage was a potential decrease in the rate of extravasations. But, this has never been provably demonstrated. You can certainly find studies that say it’s helpful, but you can find an equal number of studies saying that there’s no benefit. So depending on the research and anecdotal evidence you utilize to support your opinion, you could go either way on this. However, from my point of view, I would say that if you cannot demonstrate a statistically significant benefit to warming the contrast, then it’s not worth wasting the resources in doing so.
Try to think of it this way. Why would we want to introduce an additional element into the complex process of scanning a patient. Maybe some of you awesome Techs think it’s no big deal and super easy to use a contrast warmer and everyone should do it. OK, fine, but not everyone is as comfortable as you are in your training and workflow and many Techs I know, still feel uncomfortable at times when injecting patients. Just think of all the steps in getting a scan done. You have a CT order which needs to be cross checked with the patient’s id and make sure the order matches the reason for the exam. You have a protocol question to think about on contrasted exams. You have to consider the flow rate, the amount of contrast to be injected, IV site and IV size to consider. You have to check renal function and take into account any patient allergies. You gave to properly load the contrast into the power injector to avoid an air embolism. You have to properly position the patient and make sure the dose is optimized to the patient’s size. So given all these and many other things to be thinking about before injecting and scanning the patient, why would anyone want to complicate the process further and introduce another variable into the mix when there is no statistically significant evidence of a benefit. More equipment and more steps added to the complex process of scanning a patient requires more work for the technologist and introduces another potential way errors can be made. So, if you are still in favor of contrast warming, I urge you to really consider, WHY? And remember, this decision not only affects you, it affects all the CT Techs in your institution. You might be stellar in every way, and I have worked with some of the best, but as you know, not all techs are as organized and skillful as you are and they scan patients too. So with a lack of clear evidence for doing something, I favor not doing it. Just some food for thought. Anyway, I figured you’d enjoy knowing there’s another research study out there demonstrating that you don’t need to warm contrast and it also makes me feel better about my decision not to introduce warming at my imaging centers.
Now, if you want to learn all about the numerous details involved with giving contrast, i.e. the drug that you’re injecting into patients, well then I have you covered with a fantastic course to check out. It’s called the CT Contrast Course and you can learn more about it by watching a very short video at www.CTcontrast.com. This course will teach you everything you should have learned about contrast before you started your CT rotation. It’s taught by me, a radiologist with over 15 years of experience. I distill the 130 page ACR contrast manual and use my personal experience to only teach you what you really need to know and eliminate all the fluff. And on top of all that awesomeness, you can earn 2.25 ASRT approved Category A CEU’s for your effort. So if you’re still uncomfortable at times about injecting patients with contrast or feel like your training or education on contrast was lacking, then try out this course which comes with a 30 day, no questions asked, money back guarantee. I promise it’ll make you feel a whole lot better and much more knowledgable about using IV contrast.
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