CT

The following is intended to serve as a guideline for performing diagnostic studies that require contrast medium. Each case is unique and there will be times when the benefit of information gained from contrast administration will supersede the potential risk of reaction or renal toxicity. The following guidelines may not apply in these cases or in life-threatening emergencies.  If contrast media administration is required for a life-threatening diagnosis, then it should not be withheld based on kidney function.

The decision to give IV contrast is often multifactorial, and the clinical scenario is often the most important piece. We want to adhere to the Cr guidelines for outpatients and non-emergent exams wherever possible. However, the Cr guidelines are simply guidelines, and if there is an emergent study that the clinical team feels needs to be done (and requires IV contrast e.g. PE protocol), these guidelines can be over ridden based on the clinical need. It is reasonable to consider an alternative test if it can be safely and expediently done, but we don’t want to delay care and sometimes CT is the best exam in an unstable patient. While we know that acute kidney injury (AKI) or eGFR<30 are the main risk factors for contrast induced AKI, the absolute risk is not clear, may be overstated, and is likely outweighed by the risk of delay in diagnosis in emergent cases. This warrants a conversation with the clinical team about the need and the urgency, but if deemed an emergency without reasonable alternative exam, it is ok to proceed. On the flip side, as we have discussed before, if a study is ordered without IV contrast (but you think it needs it and you don’t see a contraindication), a conversation with the referring team can help clarify the clinical context before making changes to the order or protocol. If you are in doubt, you can always contact the fellow or attending on call (or me if it is a CT/contrast issue) to help.

1. A current creatinine level must be available for all inpatients and for outpatients over 6o years of age prior to administration of intravenous contrast. “Current” is defined as within one month for outpatients and within one week for inpatients. Routine ED patients require a same day creatine. Please also reference a complete list of the recommended indications for measurement of serum creatinine (Who must have a creatinine level prior to IV contrast?)
2. Patients with an elevated creatinine should receive intravenous contrast only if absolutely necessary. The following table provides a guideline for the use of contrast by type relative to the patients creatinine (mg/dL) or eGFR (%):
   

   UW Guidelines for Contrast Selection

   Diabetic

   Contrast	Creatinine	eGFR
   Iohexol	≤ 1.4	> 50
   Iodixanol	1.4 – 1.8	50-40
   No Contrast	> 1.8	< 40

   Non-Diabetic

   Contrast	Creatinine	eGFR
   Iohexol	< 1.8	> 40
   Iodixanol	1.8 – 2.4	40-30
   No Contrast	> 2.4	< 30

3. For an acutely traumatized patient for whom there is insufficient time to obtain a creatinine level, it is understood that the benefit of making an emergent diagnosis of a life-threatening injury outweighs the risk of contrast nephrotoxicity.
4. Patients who have chronic renal failure and are on chronic dialysis may receive contrast. While the timing of contrast administration is not dependent upon dialysis, it is preferable that the next routine dialysis occurs within 24 hours following contrast. Contrast should be avoided in patients who are experiencing acute dialysis-dependent renal failure as there is hope that renal function will recover. However, contrast may be administered in this setting if the referring physician deems it necessary.
5. Patients with multiple myeloma, sickle cell disease, homocystinuria, or active gout may receive intravenous contrast but should be well hydrated.
6. Patients who report an allergy-like reaction to contrast may be premedicated according to protocol at the discretion of the radiologist. Resuscitation equipment and drugs should be readily available.
7. Patients who report “passing out” or who needed resuscitation after past contrast injections, should have iodinated contrast only if alternative testing will not provide a satisfactory result. Same should apply to patients with allergic asthma or multiple severe allergies.
8. Contrast reactions could be potentiated by anxiety. Therefore, if a patient is exceedingly anxious prior to contrast injection, they may be premedicated with: Midazolam, 2 mg IV titrated up to a maximum of 5 mg (contraindication = glaucoma)

Jessica Robbins, June 2015

1. Ascertain the specific details of the prior reaction.  Determine:
   1. If the patient had a true reaction to intravascular contrast material
   2. Type of contrast used (if available)
   3. Type of reaction and severity
   4. Treatment and its result
   5. Level of patient anxiety
2. In addition to intravascular contrast administration, the following scenarios should be considered in patients with contrast allergy:
   1. Administration of oral contrast.  1-2% of oral contrast could be absorbed.  So for someone who has a severe contrast allergy, they should get dilute barium as an oral contrast agent.  If prior mild reaction and minimum risk of perforation/leak, no need to premedicate.  For moderate reactions or risk of peritoneal leak, consider premedication or dilute barium alternate oral contrast.
   2. Arthrograms.  Because allergic-like reactions are dose-independent, and arthrograms use a needle and cross the bloodstream, use the same premedication strategy for arthrograms that is used for intravenous media. For patients with known contrast allergies, appropriate to premedicate or switch to US if possible.
   3. Hysterosalpingograms: In patients with patent fallopian tubes, there is peritoneal spill of contrast.  Intraperitoneal contrast is absorbed (intraperitoneal=intravascular).  Because of the dose independence, premedication for HSGs should be performed in patients with known contrast allergies.
3. Determine if an examination without contrast can provide adequate diagnostic information.
4. If still convinced of the need for intravascular contrast, the service requesting  the scan should:
   1. Contact the radiologist scheduled on service for the proposed date of the study (GI/GU, CT, Angiography, Neuroradiology, or on-call resident for overnight/weekend Emergency Department patients).  If the staffing schedule is not available for the proposed date of the examination, then the Chief of the GI/GU Service (Dr. Perry Pickhardt), CT Service (Dr. Meghan Lubner), Angiography/Interventional Service (Dr. Orhan Ozkan), or Neuroradiology Service (consultant for the day) should be contracted.
   2. Discuss why an alternative imaging method will not suffice
   3. If the risk is determined to be acceptable; schedule the contrast examination and transmit prophylaxis instructions.
5. Routine Contrast Reaction Prophylaxis (12 hour):
   1. Methylprednisolone (Medrol)
      1.  32 mg by mouth at 12 and 2 hours before contrast injection.
   2. Diphenhydramine (Benadryl):
      1. 50 mg intramuscular or oral 1 hour before contrast injectionOR
      2. 50 mg (or 25 mg per height/weight indication) intravenously 15-20 min before contrast injection
         Note:  The Benadryl must be used with the proviso that the patient does not drive a car or operate heavy machinery 4-6 hours after the Benadryl is administered.
         NEJM 1987; 317: 845-849.
6. Rapid Contrast Reaction Prophylaxis (5 hours):
   1. To be used only in a truly urgent situation after discussion between the requesting service and the appropriate radiology service.
   2. The requesting service must place a note in HealthLink outlining the necessity of contrast-enhanced examination and the rapid prohpylaxis protocol.
   3. Hydrocortisone:
      1. 200 mg intravenously 5 and 1 hour before contrast injection
   4. Diphenhydramine (Benadryl):
      1. 50 mg intravenously 1 hour before contrast injection

Greenberger PA et al. Emergency administration of radiocontrast media in high-risk patients. J Allergy CLin Immunol. 1986; 77(4): 630-634.

Mervak BM, Cohan RH, Ellis JH, Khalatbari S, Davenport MS.  Premedication administered 5 hours before CT compared with a Traditional 13-hour Oral regimen.  Radiology 2017; 285(2), 425-433..

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Pheochromocytoma

Non-ionic IV contrast may be safely administered in these patients based on Bessell-Browne et al, CT of Pheochromocytoma and Paraganglioma: Risk of adverse events with IV administration of non-ionic contrast material, AJR 2007; 188: 970-974 and the ACR manual. No follow-up blood pressure monitoring is needed. Direct injection of contrast medium into the adrenal or renal artery is to be avoided however, as this may cause a hypertensive crisis.

Allergies

Patients with allergies have twice the risk of contrast reactions compared to the average patient.

Asthma

Patients with asthma have five times the risk of contrast reactions compared to the average patient.

IL-2 (Interleukin – 2 Chemotherapy)

Patients who are currently on IL-2, or have received IL-2 in the recent past, have an increased risk of delayed reaction. The reaction can occur up to several hours after the injection, and can be mild to severe. Symptoms can include hives, rash, pruritis, fever, chills, joint pain, flu-like symptoms, tachycardia, or hypotension. Symptoms can be mild and self-limited, or severe requiring hospitalization. Patients who have experienced an IV contrast reaction while on IL-2, or after IL-2 therapy should not receive IV contrast for any future imaging unless an extreme situation arises. (IL-2 patients should NOT receive steroid pre-medication. That counteracts the intended effect of IL-2).

Patients receiving IV contrast who are currently on IL-2 therapy or for 6 months following the completion of IL-2 therapy must be monitored for a minimum of two hours after their CT scan. This is usually done in the oncology clinic or in our waiting room after the scan. Six months after the cessation of therapy or after 2 uneventful contrast-enhanced scans the patient may return to normal monitoring.

Diabetes, Renal Failure, Nephrectomy, Renal Transplant

Please see the IV contrast agent guidelines.

Metformin

Metformin is an oral antihyperglycemic medication administered alone or in combination (see a list of metformin containing medications). There have been case reports of patients developing lactic acidosis after receiving iodinated contrast material while on metformin. Therefore, if a patient is on metformin, or a metformin containing medication, determine which of the two following categories describes the patient’s situation:

1. No evidence of acute kidney injury and an eGFR ≥ 30.  In this setting, metformin can be continued and there is no need to reassess renal function.
2. Acute kidney injury or severe chronic kidney disease (stage IV or stave V, eGFR <30) OR arterial catheter studies that might result in emboli to the renal arteries. In this setting, metformin should be held 48 hours after the contrast bolus/procedure. Renal function should be reassessed 48 hours after the contrast load; if renal function is normal (or at baseline), metformin may be restarted.

Active Gout

A disease that causes hyperuricemia. The patient needs to have a normal creatinine level and not be dehydrated prior to receiving IV contrast, to reduce the risk of acute renal failure. (note: patients with only a history of gout but not active are not considered at risk)

Multiple Myeloma

A malignant bone condition that causes kidney failure, dysproteinemia, abnormal proteins in the plasma, and abnormal urine proteins (Bence Jones proteins). IV contrast may cause the proteins to precipitate resulting in renal tubular obstruction and possibly renal failure. Multiple myeloma is only considered a risk factor for contrast nephrotoxicity when combined with pre-existing renal insufficiency.

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Creatinine level must be known prior to IV contrast administration. Please reinforce the importance of hydration after contrast administration.