Introduction

Contrast media are an essential aid in diagnostic medical imaging. A multitude of radiologic examinations are performed daily using these agents. They are used primarily to enhance the visibility of blood vessels, organs, and pathology in the body. Contrast media are considered pharmacologic agents, and, like any other medication, they are not without adverse effects.

Incidence

Scant data are available regarding the incidence of contrast reactions in children for at least three reasons: (1) few clinical trials with children as subjects have been performed to obtain federal approval of an agent,¹ (2) assessing symptoms, particularly mild ones in very young children, is difficult, and (3) differentiating true contrast reactions from symptoms is difficult because of sedation, synchronous medications, anxiety, and other preexisting diseases.²

In the pediatric population, use of nonionic contrast media is discriminative and exclusive when administered intravenously.³ Administration of nonionic contrast is associated with a much lower incidence of contrast media–related adverse effects.² Dillman et al⁴ reported a 0.18% incidence of acute allergic-like reactions to intravenous (IV) administration of nonionic iodinated contrast material in children. This finding is very similar to an incidence of 0.23% in the adult population reported by Cochran et al.⁵ Most of the contrast reactions are mild in both children⁴ and adults.^2,5–7 Of all the reported allergic reactions in children, 15% (<0.03% overall) were severe in degree.⁴ Fatal reactions to contrast media have occurred, but they are very rare. A large Japanese study did not blame any fatalities on contrast media in more than 170,000 injections.⁶ The very low or negligible reported fatalities likely suggest aggressive preventive measures and advancement in management of these reactions.² Delayed reactions have been described in adults and may occur between 1 hour and 2 days after contrast administration. These reactions are predominantly cutaneous and usually resolve within 7 days.^8–10

Risk Factors

As with adults, children need to be appropriately screened before contrast media are administered. Screening includes a complete and specific history from the accompanying parents/responsible adults. Attempts should be made to identify any variables that may preclude the use of the contrast media or potentially increase the eventuality of an adverse reaction to this agent. The following list outlines a few of these factors.

Other disease entities, such as pheochromocytoma, dehydration, heart failure, severe hyperthyroidism, and β-blocker therapy, that are known risk factors in adults have not been studied in the pediatric population (Box 2-1).

Pathogenesis

The exact pathogenesis of untoward events after the administration of contrast media remains obscure and poorly understood. Most of the symptoms resemble an allergic or anaphylactoid reaction to a medication or allergen. However, definitive evidence is lacking that these reactions are truly allergic reactions because antibodies and the typical allergic cascade to these agents have not been identified.¹³

Classification of Allergic-Like Contrast Reactions

Based on severity, contrast reactions can be classified as mild, moderate, or severe. Flushing and a sensation of warmth are considered physiologic responses (Box 2-2).

Mild reactions are usually of short duration and resolve without the need for any treatment. However, patients should be carefully observed until the symptoms resolve because the symptoms could progress to more severe reactions.

Moderate reactions require some form of treatment. More importantly, close observation is essential until the symptoms resolve. Vital signs should be monitored and IV access should be secured.

Severe reactions, which are rare, can be life threatening. They could present a worsening of mild or moderate reactions. Prompt and aggressive treatment may be required. The assistance of a rapid response or code team often may be necessary.

Management

In the event of any adverse reaction to contrast media, the IV contrast injection should be discontinued. All reactions and management of the reactions should be documented in the patient care notes, and notation of a contrast allergy should become part of the patient’s permanent medical record. The following protocols closely follow the American College of Radiology (ACR) guidelines for management of acute reactions in children.² The specific agents used in the management of an adverse reaction are determined by individual institutional pharmacy formulary and policy. Some institutions require the radiology personnel to call for assistance (e.g., a rapid response team) if they administer IV epinephrine for the management of these adverse reactions (given the rare incidence of these events and hence the lack of uniformity in preparedness for these reactions).^14,15 To be prepared for such reactions, weight-based dosages of the medications used for management should be posted in clearly visible areas where contrast media are administered to children. Regular review of treatment protocols and practice of contrast reaction scenarios should be performed by radiologists and staff. If at any time a patient does not respond to treatment or the situation seems troublesome, it is appropriate to seek additional medical support immediately. This support may be sought from another radiologist in the department or through activation of an institutional rapid response or code team.

Urticaria

Urticaria, which is the most common reaction to contrast media, is limited to skin and subcutaneous tissue. Worsening of symptoms can be caused by the accompanying pruritus. Findings on physical examination include:

Mild urticaria is usually self-limiting and does not require treatment.

Close observation for 30 to 60 minutes, or until resolution, is recommended because urticaria may progress to a moderate reaction. Medications may include H1-receptor blockers (such as diphenhydramine) or α-agonists (such as epinephrine). The accompanying parents/responsible adults should be cautioned about the possibility of drowsiness when diphenhydramine is administered. If urticaria is extensive, pay close attention to the patient’s blood pressure and watch for signs and symptoms of hypotension, especially orthostatic hypotension.

Bronchospasm

The patient may present with varying degrees of cough, wheezing, and/or difficulty breathing. It is most important to ensure the presence of an adequate airway. Six to 10 L/min of oxygen should be administered via a face mask. Vital signs should be monitored. Medications may include β-agonists (i.e., bronchodilators), subcutaneous epinephrine for mild symptoms, and IV epinephrine for more acute and severe symptoms.

Facial or Laryngeal Edema

Swelling of the face may be mild without any significant progression. At this time, only observation may be required. An adequate airway and IV access should be secured. However, if the patient presents with other symptoms such as varying degrees of cough, hoarseness, dysphagia, and/or difficulty breathing, more aggressive measures need to be taken. Medications include subcutaneous, intramuscular, or IV epinephrine. The patient should be closely monitored.

Pulmonary Edema

The patient may present with tachypnea, tachycardia, shortness of breath, diaphoresis, agitation, and/or bibasilar rales. Blood-tinged sputum is a late-presenting sign. The airway must be secured and supplemental oxygen should be administered. Medications may include diuretics. Pulmonary edema is a severe response that usually should involve a rapid response or code team.

Hypotension with Tachycardia (Anaphylaxis)

Anaphylaxis can be a life-threatening response to contrast media. Symptoms may include difficulty breathing, chest tightness, a thready pulse, a rapid or irregular heart rate, dizziness, hoarseness, and/or loss of consciousness. The rapid response or code team should be called the moment this adverse effect is suspected. Meanwhile, management should be initiated with Trendelenburg positioning, securing of the airway, rapid fluid resuscitation, and administration of IV epinephrine.

Hypotension with Bradycardia (Vasovagal Reaction)

Patients may present with pallor, a decreased level of consciousness, diaphoresis, and a decreased heart rate. Management should be initiated with Trendelenburg positioning, securing of the airway, hydration, and administration of atropine if bradycardia persists (Box 2-3).