Emergency Body CT > Contrast Reactions > Contrast Reactions (2)


Contrast Reactions (2)

Preventing contrast reactions in patients with a history of contrast allergy can be accomplished by performing the scan without IV contrast when possible or by premedicating the patient. Other imaging modalities such as MRI or ultrasound may be used to answer the clinical question. Typical regimens used to prevent contrast reactions include:

1) Methylprednisolone 32 mg PO 12 hours and again 2 hours before contrast.
2) Prednisone 50 mg PO 13 hours, 7 hours and 1 hour before the exam.
3) Methylprednisolone 100 mg IV1 hour before the exam.

Anti-histamines such as diphenhydramine 50 mg IV, PO or IM may be administered one hour before the exam.

A problem which fortunately arises only occasionally, is extravasation of contrast material into the subcutaneous (of the hand or forearm) during injection. While not usually a significant problem, this occurrence should prompt an evaluation by a doctor to rule out signs or symptoms of compartment syndrome. Such findings would include pulselessness, pallor, pain, and paresthesias. If any concern about compartment syndrome remains after examining the patient, a surgical consult should be obtained.

The most common finding is some swelling around the injection site representing the extravasated contrast. In the absence of other significant findings, the patient can be instructed to keep the affected extremity elevated and to apply a cold pack to the area. The patient and/or referring service should also be made aware of the potential for later development of compartment syndrome and instructed to seek medical care if any of the previously mentioned symptoms develop.

A second and rare reaction following contrast extravasation is ulceration and sloughing of the skin around the injection site. This occurs much more frequently with ionic contrast agents. A plastic surgery consult is indicated at first suspicion of this complication.

 

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