Hypersensitivity reactions to contrast media, though infrequent, pose critical risks in diagnostic imaging and demand a robust, standardised approach. These reactions may be immediate or delayed, mild or life-threatening, and are typically linked to iodine-based, gadolinium-based or ultrasound contrast agents. The European Society of Urogenital Radiology (ESUR) Contrast Media Safety Committee has updated its guidelines to improve clinical response, treatment protocols and documentation practices for managing these reactions in adults.
Understanding and Classifying Reactions
Hypersensitivity reactions (HR) are categorised based on timing and severity. Immediate hypersensitivity reactions (IHR) typically occur within one hour of contrast media administration and can progress rapidly. These may involve IgE-mediated or non-IgE-mediated immune responses, presenting as urticaria, bronchospasm or even anaphylaxis. In contrast, non-immediate hypersensitivity reactions (NIHR) appear from one hour to several days post-exposure and are mostly cutaneous, such as maculopapular rashes.
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Severity classification follows the American College of Radiology (ACR) scheme for practical application in radiology settings, distinguishing mild, moderate and severe symptoms. This classification aids in determining the urgency of treatment and monitoring. While mild reactions often resolve without intervention, moderate to severe reactions require immediate management and careful documentation to guide future care decisions.
Management Protocols and Drug Use
Preparedness is central to managing HR effectively. Radiology departments must be equipped with a resuscitation trolley, essential drugs including intramuscular adrenaline and H1-antihistamines and clear treatment flowcharts. For IHR, adrenaline remains the cornerstone of treatment, especially for anaphylaxis, administered intramuscularly at 0.5 mg in adults. Beta-blocker use may limit adrenaline effectiveness, necessitating glucagon or dobutamine.
Supportive measures such as oxygen therapy, fluid administration and patient positioning play vital roles. Salbutamol may be added for bronchospasm, and corticosteroids considered to prevent biphasic reactions, although evidence of their acute efficacy remains inconclusive. For NIHR, treatment is typically symptomatic, involving oral or topical corticosteroids and antihistamines. Severe cutaneous adverse reactions (SCARs), though rare, require immediate dermatological consultation.
Due to the low incidence of these events, staff may lack practical experience. Simulation-based training has been shown to be more effective than didactic methods in preparing healthcare providers to recognise and treat contrast reactions. Regular refresher sessions ensure familiarity with emergency protocols and accurate drug dosing.
Documentation and Risk Assessment
Accurate documentation of HR is essential to prevent recurrence and support allergological evaluation. Key details include the contrast agent’s name and dose, type and timing of the reaction, symptoms, vital signs, treatment administered and patient response. This information should be entered into the electronic health record and, in serious cases, reported to pharmacovigilance authorities.
Risk assessment prior to contrast administration is critical. The most significant predictor of future HR is a history of previous reaction to the same agent. Other factors—such as a history of allergies, female sex, age below 50 or underlying conditions—offer weaker predictive value but may compound risk in combination. Identifying high-risk patients enables proactive measures, such as alternative imaging strategies or contrast agent substitution.
Special caution is warranted in patients receiving cardiac imaging who are premedicated with beta-blockers. These individuals are more susceptible to severe reactions, and standard treatment may be less effective. In such cases, procedures should be scheduled when staff and emergency resources are most available, ideally during daytime hours in hospital-based imaging units.
Hypersensitivity reactions to contrast media, while uncommon, can have serious consequences if not promptly and appropriately managed. The updated ESUR guidelines underscore the importance of preparation, classification, treatment protocols and comprehensive documentation. Radiology personnel must receive regular training, and departments must maintain readiness with adequate supplies and clear action plans. With these measures in place, the risks associated with contrast media can be effectively mitigated, ensuring safer diagnostic procedures for patients.Haut du formulaire
Source: European Radiology
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