Tuesday, February 25, 2014

Contrast Allergy and Emergency Premedication for CT contrast

Emergency premeditation for CT contrast is an important step before many diagnostic exams in a large percentage of our patients.

In every patient with a reported history of allergy to iodinated contrast material, make every reasonable effort to clarify the nature and severity of the reaction in person with the patient. If the patient is not able to provide a history, obtain history from family member/NOK/POA. The ER physician should be last source of this information. It is you who will be responsible for managing an acute life threatening contrast reaction in the event this occurs, NOT the ER physician.

If patient has a history of a severe anaphylactic reaction following IV iodinated contrast, IV contrast is contraindicated (not even with premedication).*

The following are Emergency Medication Protocols set forth by the ACR. They are listed in order of DECREASING desirability.

1. Methylprednisolone sodium succinate (Solu-Medrol®) 40 mg or hydrocortisone sodium succinate (Solu-Cortef®) 200 mg intravenously every 4 hours (q4h) until contrast study required plus diphenhydramine 50 mg IV 1 hour prior to contrast injection.

2. Dexamethasone sodium sulfate (Decadron®) 7.5 mg or betamethasone 6.0 mg intravenously q4h until contrast study must be done in patent with known allergy to methylpred-nisolone, aspirin, or non-steroidal anti-inflammatory drugs, especially if asthmatic. Also diphenhydramine 50 mg IV 1 hour prior to contrast injection.

3. Omit steroids entirely and give diphenhydramine 50 mg IV.

Note:  For options 1 and 2, the minimum accepted emergency premedication window using IV steroids is 4 hours. This is a frequent source of contention between the ED physician and radiologist. If contrast will be administered less than 4 hours after the IV administration of prophylactic steroids, it is considered a fruitless exercise.

Note: Option 3 is the least proven and therefore the least preferred. The advantage to this method is the theoretical “immediate protection” against severe allergy/anaphylaxis. Utilize this sparingly and in the most emergent, uncertain and time sensitive of situations.

*Weigh the risks and benefits of any decision and please, if you do anything for the patient, do no harm. You will encounter tough decisions in a fast paced environment during your time in the ER. If you have a complex multi-trauma patient who is “crashing” as they are hoisted upon the CT scanner, but have a history of anaphylaxis to IV contrast dye, the above guidelines may or may not apply. Use your best judgment as a physician. Maybe a non-contrast exam will suffice? If contrast will really make a difference in the patient’s management, squirting some Benadryl into their IV before giving contrast may offer some protection. Keep in mind that many of the sickest patients are already intubated and on vasopressors.

Other tips:

1) Shellfish allergy in itself has no specific relation to, nor predisposition for an allergy to IV contrast. If the patient is susceptible to many allergens (pollen and shellfish and peanuts and etc, etc, etc) and has never received IV contrast, premedicating them is a probably a good idea.

2) Giving IV contrast to a nursing mother is very, very unlikely to have any ill effects for mother and baby, but mom can wait 12-24 hrs after receiving contrast to resume breastfeeding, mainly for “peace of mind”.

Hope that this provides some basic information on emergency premeditation for CT contrast.

Good luck.


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