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Contraindications/Interactions
1.
I have a patient with hematuria and suspected TCC on a retrograde pyelogram,
who requires renal CTA. She also has a known (contralateral) pheochromocytoma.
What do you recommend with respect to the use of IV contrast in Pheo
patients? Should they be premedicated? With what? Or should we just
keep antihypertensives on hand, (which one?) and observe the patient
for 30 - 60 minutes post injection?
| Answer:
With nonionic contrast, the chance of a reaction is indeed very
low. But, we would still recommend premedicating these patients.
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2.
Is there a contraindication to giving intravenous contrast in an outpatient
CT facility? Specifically- with respect to asthmatics.
| Answer:
There is no difference between our use of contrast at any of our
locations. The same guidelines apply; although, we are all aware
of the isolation of many clinics. In these cases, especially, the
use of nurse is very helpful. |
3.
Any complications with using IV contrast on a patient while IV heparin
is being used? How about using any IV/oral medication with IV contrast?
| Answer:
There is no issue with heparin except to be careful with IV placement
and during the injection. The key meds that are problematic with
IV contrast are glucophage (metaformin) and NSAID's. |
4.
I was wondering what your protocol is regarding patients with possible
pheochromocytoma. I've always understood one is not to inject IV contrast
on know pheo patients. Is that correct?
| Answer:
With nonionic contrast, the chance of a reaction is indeed very
low. But, we would still recommend premedicating these patients.
|
5.
What do you recommend for patients with Sickle Cell Anemia and those
with Sickle cell trait? Are they handled alike?
| Answer:
For Sickle Cell Anemia, because of the frequency of crisis, are
handled more carefully than Sickle Cell Trait. Although there has
been some discussion about whether you can use contrast in patients
with Sickle Cell Disease, as long as patients have baseline normal
renal function, the use of contrast is typically not an issue. |
6.
What is your policy regarding IV contrast and pregnancy (assuming the
CT is medically necessary)? Do you give it or reduce the dose? Is it
actually harmful to the fetus?
| Answer:
In regards to pregnancy, there is no known long term effect to the
fetus with IV contrast. We do of course limit the use of CT in the
pregnant patient, but the key is that we give enough contrast to
make a correct diagnosis. It is optimal to minimize contrast, but
the key is to make the correct diagnosis. I am not sure if Omnipaque
or Visipaque would be best in this situation, but we use Visipaque
as it provides equal or better quality images in the typical applications
used in the pregnant patient (i.e. PE) |
7.
Do you have any issues with giving IV contrast in patients who have
glaucoma? Is there a historical problem?
| Answer:
There is no issue to my knowledge of IV contrast and glaucoma. |
8.
What is your recommendation for IV injection of contrast media in diabetic
outpatients taking Glucophage (metformin).
| Answer:
Standard recommendation is to stop glucophage that day and wait
24- 48 hours until you begin retaking it. Per the drug manufacturer,
they would suggest checking a creatinine level before the patient
begins re-taking the drug. |
9.
What is JH's policy on breastfeeding mom's and contrast injections?
| Answer:
The ACR has stated that in reality, no delay is necessary, but to
be conservative, a 24 hour delay is all that is needed after contrast. |
References
Michael A. Bettmann Frequently Asked Questions: Iodinated Contrast Agents
RadioGraphics 2004; 24: 3-10.
- Summary:
Many of the questions presented here are addressed in this recently
published Radiographics article, which serves as an excellent reference.
Mukherjee
JJ. Peppercorn PD. Reznek RH. Patel V. Kaltsas G. Besser M. Grossman
AB. Pheochromocytoma: effect of nonionic contrast medium in CT on circulating
catecholamine levels. Radiology. 1997; 202(1):227-31.
- Summary:
Summary: This was a small study, including 10 patients with
pheochromocytomas and related tumors compared to six healthy
volunteers. Twenty-four hours prior to the CT scan, all patients were
administered phenoxybenzamine hydrochloride (an alpha-adrenoceptor
antagonist) intravenously. Iodinated contrast (iohexol) and control
(saline) were infused on 2 different days, and plasma catecholamine
levels were sampled at baseline and 8 times up to 60 minutes following
the infusion. Results showed no statistically significant rise in
epinephrine or norepinephrine levels in the patients or the control
subjects. However, 2 patients did have a "substantial"
increase in
norephinephrine levels after contrast infusion. In light of
the
unpredictable catecholamine release among the patients, the authors
advise administration of oral blockade with alpha- and
beta-adrenoceptor antagonists to all patients with biochemically proven
catecholamine-secreting tumors.
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