Follow-up from Last Episode

We did a discussion of Contrast-Associated Nephropathy on episode 369, here's some follow-up

One ? occurred to me, how does your risk assessment change when all of the patients decreased GFR appears to be an acute situation from a prerenal azotemia and the patient has no known intrinsic kidney disease.

How about if they have a real kidney hit, but it is all from their acute critical illness, not baseline kidney disease.

How about kidney transplant patients

from Justin Morgenstern

Hi Scott and Joel,

Thanks for the excellent podcast. Although I think you were careful in your framing of the question, and so the conclusions as stated are probably entirely correct, and I think your overall message is good, I worry about the consequences of that conclusion that you don’t fully explore.

By focusing only on the tiny subset that you do (the patients with very low eGFRs) are we overlooking the significant harms to all other patients that comes from that focus? In order to identify this subset, we require all patients to have blood work. We delay important scans, and therefore important diagnoses and important treatments, focused on this tiny minority.

And although it is true that you cannot prove contrast doesn’t hurt kidneys, can you find any evidence that it does? In the history of medicine, is there a single properly controlled study that shows any harm from contrast? I might be missing one, but I have been covering this for a long time, and I believe that every study ever conducted with a control group shows no difference.

The most recent study focused specifically on the group you raised as a question at the end: acute kidney injury. (Ehmann 2023, PMID 36715705). They only looked at sick patients with acute kidney injury in the ED, and in a propensity matched analysis, there was no difference at all (LR exactly 1). The outcomes were the same for patients with eGFR <30.

Therefore, although I think you can correctly say it is impossible to prove contrast is definitively safe, it is also completely appropriate to say that every bit of properly controlled evidence that we have suggests that there is no risk from contrast. However, there is a clear harm. In my career, I have seen multiple patient die after a delayed diagnosis of a critical disease, because a CT was delayed waiting for blood work to be done. Aside from the dramatic outcomes, patients sit for hours, completely unnecessarily, because of this added step, in essentially every ED in the world.

I think this conversation needs to be framed somewhat differently. There are clear harms from talking about eGFR based contrast cut offs, there is no evidence of harm from contrast, and indeed there is a mountain of evidence that contrast has no effect on kidneys. I think the only sensible clinical conclusion at this point is that, until someone can demonstrate there is a real harm, and always with the application of clinical judgement, we should proceed as if contrast has exactly no impact on kidneys and completely drop the requirement for bloodwork.

To me, it doesn’t seem close. The harms seem to very clearly outweigh the risks. (Of course, if we move to a world that abandons routine blood work before IV contrast, clinicians are still welcome to use clinical judgement for individual patients).

All the best
Justin

And he continues…

I know that we are on the same page for the patient that you are talking about. And I actually agree with everything you are saying. If a scan isn't 100% necessary, or if there is an adequate alternative (ie VQ scan), it might make sense to consider contrast exposure in these high risk patients.
However, in the absence of any evidence of harm, my concern about any conversation that focuses on eGFR is the underlying assumption that eGFR is important, which subtly reinforces the practice of getting bloodwork before scans, which ultimately makes it harder for us to see practice change.
If our baseline practice was logical, I would love your discussion. However, our baseline practice is causing so much harm than I think any discussion of eGFR in this context is likely to reinforce the current (harmful) practice.
Hope that makes sense. Looking forward to part 2
Justin

Contrast Reactions

i Dr. Weingart,

I have been a practicing EM physician for the past 13.5 years in busy community practice and I encountered a difficult clinical decision the other day and was curious your thoughts on it.

I am wondering what your practice is when you need a time-sensitive imaging study that uses IV contrast dye and a patient reports a recent, life-threatening allergic reaction to contrast dye? My case involved an older gentleman with COPD who presented with several hours of severe chest pain followed by onset of L hemiparesis. My initial concern was, of course, dissection. But the patient told me he had had an immediate cardiac arrest following administration of IV contrast dye at an outside hospital about 2 years ago. My IR and Neuro colleagues suggested intubating him and giving him the IV contrast anyway. While that strategy would protect his airway ,I was still quite concerned about the potential cardiac and other vascular effects of possible anaphylaxis, even with pre-treatment. From my quick research and discussions with consultants, MRI would be a decent replacement study for aortic dissection, but was not adequate for determining if he was an interventional candidate for his stroke symptoms.

I would love to know your thoughts on this situation. I would be curious to hear your take on how to consent a patient for this type of thing too.  (i.e. knowing that he had a cardiac arrest secondary to contrast previously). Because it seems to me that even if you have your epi and intubation ready to go, there’s still a risk that something bad could happen and the patient would be understandably nervous. Just wondered how you would discuss this with a patient in a time- sensitive emergency situation. Thanks so much!

Jackie LNW

ACR Contrast Media Guide

Usually Updated Yearly

Contrasts

HOCM vs. LOCM vs. IOCM

1985-Early 2000's

Likely ionic high-osmolar agent

After 2010

Which agent, if you can find out, change the agent

List of Contrast Agents

Risk Factors

Allergies, asthma, prior reactions

Iodine Allergies / Shellfish Allergies

Take shellfish (actually from tropomyosins) and skin preps off of the CT screening lists

Reactions

allergic (anaphylactoid) or physiologic

mild, moderate, severe

Mild

Flushing, urticaria, pruritis, n/v, headache, dizziness

Moderate

Bronchospasm, facial or laryngeal edema

Severe

Respiratory or circulatory collapse, VT (Kounis Syndrome?)

Life threatening reactions will be seen in 20 minutes in almost every case (ACR Contrast Manual)

The estimated risk of a severe reaction to LOCM or IOCM is approximately 4 in 10,000 [ 10.1016/j.rcl.2016.10.012 ]

Vomiting

Enormous study shows no benefits to fasting [10.1186/s13244-022-01173-z]

Society Recs (from Davenport Editorial)

The current American College of Radiology guidelines state:

“The utility of premedication in high-risk patients is uncertain…(but) premedication may be considered in (some) settings and scenarios (ie, prior immediate hypersensitivity or unknown-type reaction to the same class of contrast medium)”

The current European Society of Urogenital Radiology guidelines state:

“Premedication is not recommended because there is not good evidence of its effectiveness”

[European Society of Urogenital Radiology. ESUR Guidelines on Contrast Media v.9.0. Available at: http://www.esur.org/esur-guidelines/ ]

The 2020 Joint Task Force on Practice Parameters for Allergy and Immunology state:

“We suggest against routinely administering glucocorticoids and/or antihistamines to prevent anaphylaxis in patients with prior radiocontrast hypersensitivity reactions (conditional recommendation, certainty rating of evidence: very low),” and “Higher certainty evidence is needed to better inform practice”

ACR Rapid Prep

Methylprednisolone sodium succinate 40 mg IV or hydrocortisone sodium succinate 200 mg IV immediately, and then every 4 hours until contrast medium administration, plus diphenhydramine 50 mg IV 1 hour before contrast medium administration. This regimen usually is 4-5 hours in duration. [ACR Contrast Media Guide]

• Mervak et al. showed that the 5 hour prep was non-inferior to the 13 hour protocol, but there was no placebo group, so we don't know if either of them was actually effective [10.1148/radiol.2017170107]
• Mervak estimated to prevent one death in a patient with prior reaction would have a NNT Of 56,900, but based on historical controls rather than studied
• Prep affects mild reactions, but not moderate or severe, Lasser et al. showed no benefit to pretreatment for moderate or severe reactions [Lasser E.C., Berry C.C., Mishkin M.M., et. al.: Pretreatment with corticosteroids to prevent adverse reactions to nonionic contrast media. AJR Am J Roentgenol 1994; 162: pp. 523-526 10.1016/j.rcl.2016.10.012]

Mild Reaction Prevention

Antihistamines or contrast sub or both all worked with the latter working best [10.1148/radiol.2018172524]

McDonald Study

Steroid Prep vs. Substitution

Editorial on the McDonald Study

Davenport & Weinstein

Great Review Article

• 10.1016/j.rcl.2016.10.012

Strategy for High Risk Patients

Use alternative studies (MRI?, Ultrasound?, Non-Con CT?)

Switching to a different contrast seems to be the most efficacious move

Use Iso-osmolar, non-ionic contrast, iodixanol (Visipaque)???

When recording reactions in the chart, put the actual name of the contrast

We need to be able to take ownership of contrast liability

What to Do if you Respond to a Contrast Reaction

ACR Contrast Reaction Card

Contrast Reaction Card

Additional New Information

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Scott Weingart, MD FCCM

Editor-in-Chief, at EMCrit.org

An ED Intensivist from NY.
Professor
Nassau University Medical Center
No conflicts of interest (coi).

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