Treatment of Contrast Media Reactions
Michael A. Bettmann
General Principles (1)
1. The radiologist should have the expertise, experience, and equipment to treat most (i.e., non-life-threatening) contrast media reactions without assistance.
2. Access to expertise and equipment for effectively responding to life-threatening reactions should be readily available: fully trained, advanced cardiac life support (ACLS)-certified personnel as well as code cart and code team.
3. The medications and equipment to treat all reactions, from minor to acutely lifethreatening, must be readily available and regularly updated. These include commonly needed medications (diphenhydramine, β-agonist inhalers, atropine, and epinephrine) and equipment (endotracheal tubes, laryngoscope, monitor, external pacemaker, and defibrillator). If not in the room, all this equipment must be located so it is accessible within seconds to the suite in which contrast is administered.
4. The response time to the treatment should be minimized (1). Not all contrast reactions present with a classical complex of signs and symptoms. Failure to consider and recognize that a patient is actually having an adverse reaction may delay the appropriate treatment (2). Conversely, the reaction must be accurately diagnosed and understood—an anxiety reaction may mimic an early anaphylactoid one.
5. Three basic requirements for all patients
a. Know the patient.
b. Recognize that there is a problem.
c. Be prepared to deliver treatment and call for help quickly. (Know the ABCs of basic life support [BLS]: airway/assessment, breathing, and circulation.)
d. Know exactly where the code cart, with automatic external cardioverterdefibrillator (AECD), is located; ensure it is regularly inspected and updated (2,3).
6. Three reactions of greatest concern, as all may mimic cardiovascular collapse
a. Anaphylactoid reaction: life-threatening
b. Vasovagal: more common, must be treated to resolution
c. Anxiety or syncope: diagnosed by exclusion, but do not immediately treat with epinephrine
Know the Patient
1. Before the procedure, inquire about prior exposure to iodinated contrast material, previous adverse reactions, and relevant history.
a. Does the patient have a history of asthma? If so, is the patient actively wheezing? Contrast media can provoke bronchospasm and worsen preexisting airway constriction.
b. Does the patient have a strong history of multiple and/or severe allergies? This increases the risk of an adverse reaction to contrast agents.
c. Does the patient have a history of coronary artery disease, aortic stenosis, or other significant cardiac problem? Contrast material can compromise cardiac function (4).
d. Is the patient being treated for congestive heart failure? Contrast material will increase the effective circulating volume and may cause pulmonary edema in the poorly compensated patient.
e. Are there any reasons why the patient may have compromised renal function? (See Chapter 65.) This includes known renal dysfunction, bladder outlet obstruction (male or female), long-term diabetes, recurrent infections, or renal calculi.
f. Does the patient have any other major active medical problems? Is the patient particularly anxious or unable to cooperate?
2. The radiologist performing the procedure should have knowledge of the patient’s routine medications. Some medications may mask the symptoms of a contrast reaction.
a. β-Blockers slow the heart rate and block the tachycardiac response to physiologic stress. β-Blockade blunts the effects of epinephrine (an α- and β-agonist), requiring increased doses to achieve similar physiologic effect. Once the β-blocker effect is overcome, an unopposed α-adrenergic effect of epinephrine predominates, with a marked increase in peripheral vascular resistance and a subsequent hypertensive response.
Additionally, vasovagal reactions are characterized by hypotension and bradycardia. In patients on β-blocker therapy, an anaphylactoid reaction may be misjudged as a vagal reaction because of the absence of tachycardia.
b. Calcium-channel blockers are frequently prescribed for hypertension, coronary insufficiency, and arrhythmias. They are peripheral vasodilators; correction of hypotension by fluid replacement may be more difficult due to persistent peripheral vasodilation.
c. Metformin, an oral hypoglycemic agent, can rarely lead to lactic acidosis, which is fatal in a high percentage of patients. Because of the renal excretion, it has been thought to be contraindicated in patients with elevated serum creatinine, although this caution is being reconsidered, based on empirical information (5,6,7). Current U.S. Food and Drug Administration (FDA) recommendations still indicate that metformin should be stopped for 48 hours at the time of contrast administration (5) (see Chapter 65).
Recognize that There Is a Problem
1. Look for both the classical/expected and the more subtle signs that the patient is having an adverse reaction.
a. First, talk to the patient and assess ABC status. Many “reactions” may simply be manifestations of anxiety, with resultant tachycardia, tachypnea, and light-headedness.
b. Dermal reactions: urticaria, pruritus, diffuses erythema, skin flushing
c. Angioedema may present with increased production of tears, difficulty in swallowing, nasal congestion, or laryngeal edema with hoarseness. Facial edema may also, rarely, occur.
d. Bronchospasm occurs almost solely in patients with asthma. It is characterized by dyspnea, sometimes tachypnea and end-expiratory wheezing. In contrast, laryngospasm, which is less frequent and more concerning, is characterized by stridor or inspiratory wheezing.
e. Sudden loss of consciousness may be due to central nervous system (CNS
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