A 42-year-old woman with a history of asthma and atopy undergoes contrast-enhanced CT abdomen for suspected appendicitis. Within 5 minutes of intravenous iodinated contrast injection, she develops urticaria, mild wheezing, and facial oedema. Her blood pressure is 128/82 mmHg, heart rate 98/min, and oxygen saturation 96% on room air. What is the most appropriate immediate management?

Explanation

## Acute Contrast Reaction: Immediate Management ### Clinical Presentation Classification This patient is exhibiting signs of an **acute moderate (non-anaphylactic) contrast reaction** with cutaneous and respiratory involvement: | Feature | Finding | Significance | |---|---|---| | Urticaria | Present | Cutaneous manifestation | | Wheezing | Mild | Early airway involvement | | Facial oedema | Present | Risk of airway compromise | | BP/HR | Stable | Not yet anaphylactic shock | | O₂ saturation | 96% | Mild hypoxaemia risk | | Risk factors | Asthma + atopy | Predispose to severe progression | **Key Point:** Acute contrast reactions span a spectrum from mild (urticaria alone) to severe (anaphylaxis with shock). **Any respiratory or angioedema symptoms mandate immediate epinephrine**, regardless of blood pressure stability, because anaphylaxis can progress rapidly. ### Immediate Management Algorithm ```mermaid flowchart TD A[Acute contrast reaction]:::outcome --> B{Respiratory symptoms<br/>or angioedema?}:::decision B -->|Yes| C[Stop imaging immediately]:::action C --> D[Establish IV access]:::action D --> E[IM epinephrine 0.3-0.5 mg<br/>1:1000 solution]:::action E --> F[Continuous monitoring<br/>BP, HR, O2 sat, airway]:::action F --> G{Improvement?}:::decision G -->|Yes| H[Observe 4-6 hours<br/>H1/H2 blockers + corticosteroids]:::action G -->|No| I[Repeat epinephrine q5-15 min<br/>Consider IV epinephrine infusion]:::urgent B -->|No - urticaria only| J[Observe closely<br/>IV access ready]:::action J --> K{Progression?}:::decision K -->|Yes| E K -->|No| H ``` **High-Yield:** **Epinephrine is the first-line drug for any acute contrast reaction with respiratory or angioedema symptoms.** It must be given intramuscularly (not IV) at 0.3–0.5 mg of 1:1000 solution. Do not delay for antihistamines or corticosteroids. **Clinical Pearl:** Patients with asthma and atopy have a 5–10 fold higher risk of contrast reactions. Mild wheezing + facial oedema = **treat as anaphylaxis until proven otherwise**. Anaphylaxis can deteriorate within minutes. **Mnemonic — REACT:** **R**espiratory symptoms = epinephrine now, **E**stablish IV access, **A**ddress airway risk, **C**ontinuous monitoring, **T**reat with H1/H2 blockers and steroids after stabilisation. ### Why Other Options Fail - **Continue imaging:** Contraindicated; imaging can be resumed only after the reaction has fully resolved and patient is stable for ≥4–6 hours. Continuing exposes patient to further contrast and delays treatment. - **IV diphenhydramine alone:** Antihistamines are **adjunctive**, not first-line. They do not reverse anaphylaxis and delay epinephrine administration. Wheezing + oedema require immediate epinephrine. - **Discontinue and transfer to ICU:** While discontinuing contrast is correct, ICU transfer is premature if epinephrine is given promptly and patient responds. ICU is appropriate only if anaphylaxis progresses despite epinephrine or if airway is compromised.