Iodinated Contrast Reactions: Treatment Considerations
Written by Neil T. Specht, M.D.
Suddenly being summoned to evaluate and treat a patient with an acute systemic reaction to a contrast injection can be one of the most frightening episodes encountered in the practice of radiology. Although we are knowledgeable of the treatment and prevention of such reactions, many of us are not truly prepared to react to and control a severe contrast reaction should one be encountered. Especially in an office setting, where access to pro .medical intervention might be limited, our preparedness, prompt recognition, and ability to treat these life-threatening occurrences is essential for patient well-being.
Systemic reaction to contrast injection is largely based on activation of the histamine bradykinin and complement systems. The overall incidence of contrast reactions is estimated at 5-10% for high osmolality contrast media (HOCM) and 1-3% for low osmolality contrast media (LOCM) with the vast majority of reactions being limited to minor idiosyncratic and non-anaphylactoid varieties (i.e., nausea, vomiting, itching, rash/hives and headache). Treatment for these reactions are largely based on supportive or symptomatic treatment. Life-threatening reactions (laryngeal edema, hypotension, unresponsiveness, cardiac arrest), nearly all of which have an onset that is immediate to within 20 minutes of the contrast injection, are estimated at approximately 1 per 1,000 injections for HOCM and 1-2 per 10,000 injections for LOCM. The overall death rate directly related to contrast injection reaction is estimated at 1 per 100,000 injections.
Prior to initiation of a contrast study, a medical history should be obtained to aid in the selection of type of contrast media (HOCM versus LOCM) and possible need for pre-medication treatment prior to contrast injection. In patients with a history of diabetes, cardiovascular disease (ASHD, valvular disease, cardiomyopathy, rhythm disturbances, etc.), renal insufficiency, asthma, previous serious allergic reaction to any outside stimulus (including prior contrast reaction), other debilitating systemic disease, or those patients at risk for extravasation, use of LOCM is recommended. In patients with prior history of anaphylactic reaction to any inciting agent, if a contrast examination is deemed necessary, patients should be premedicated with corticosteroids and the study should optimally be performed in a hospital setting where a support team is readily available.
Premedication with corticosteroids has been shown to reduce the incidence and severity of contrast reactions. Several premedication regimens have been developed with the two most popular regimens using a dosing schedule of 13, 7 and 1 hour prior to contrast injection, or 12 and 2 hours prior to contrast study. For optimum benefit, at least one dose should be given at least 6 hours prior to contrast injection. Diphenhydramine (Benadryl?) 50 mg IM/IV or p.o. can be used in conjunction with the corticosteroid and should be given 1 hour prior to the contrast injection. The recommended corticosteroid dosages are as follows:
|
Corticosteroid |
Route of Administration |
Equivalent Strength Dosages |
Individual Premedication Dose for Contrast Study |
|
Prednisone* |
p.o |
5 mg |
50 mg |
|
Methylprednisolone*
Medrol®
Solu-Medrol® |
p.o.
i.v. |
4 mg |
40 mg** |
|
Hydrocortisone
Cortef®
Solu-Cortef® |
p.o.
i.v. |
20 mg |
200 mg |
|
Dexamethasone† |
i.v./i.m./p.o. |
0.75 mg |
7.5 mg |
*Preferred agents, equally effective; p.o. administration route preferred
**32 mg may be used as an alternate dosage
? Longer acting, generally not the preferred agent
The response to an acute contrast reaction should be rehearsed and controlled. A well equipped room is of little help if the response is chaotic. The code/crash cart, or equivalent, should be well stocked with necessary medications and life-support equipment. There should be at least semi-annual evaluation of the medications within the emergency cart with note of expiration dates which should be maintained on an individual log and replenished as necessary. Only 1 person should be directing the response team. The response team director should designate specific room responsibilities such as:
1. Individual to activate the EMS response; call 911.
2. Medication acquisition and preparation (the need for rehearsal of the response team is required for knowledge of location and preparation of medication).
3. Airway team - initial placement of oral airway, bag-valve-mask oxygen delivery; possible later intubation.
4. I.V. access - if additional vascular access required for delivery of large volume cardiovascular support (D5W, Ringer's lactate, normal saline).
5. Treatment recorder - medications given, time administered, periodic notation of patient condition.
The initial response should follow an initial "ABCD" (airway, breathing, circulation, differential diagnosis) approach as outlined in the Advanced Cardiac Life Support protocols (as published by the American Heart Association) with any further treatment based on the specific ACLS protocols as they pertain to the condition encountered.
Recommendations for adequate preparedness:
- Rehearse and review emergency response with particular attention to specific individual duties of the members of the response team.
- Have an oral airway readily available wherever contrast is administered (e.g. attached to the CT gantry or tomographic unit).
- Know ACLS treatment protocols especially as they pertain to treatment of vasovagal reactions (severe bradycardia) and asystole.
- Review patient history carefully prior to initiation of the contrast exam in an effort to identify those at increased risk of reaction
- Crash/code carts/kits should be uniform in arrangement between multiple rooms/offices. It may be helpful to have easiest access to medications more frequently administered (e.g. ammonia inhalants, atropine, epinephrine, verapamil, adenosine).
- Know how to activate EMS/Code response whether it be in an office setting or other health care facility.
- Know practice policy for treatment and referral of contrast extravasations.
- Know practice policies and protocols related to premedication with corticosteroids.
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