Computed Tomography Test CT Contrast Media and Patient Preparation 2 — Questions and Answers
Question 1: What type of adverse reaction to iodinated contrast media involves an immune-mediated hypersensitivity response?
- Anaphylactoid (allergy-like) reaction (Correct answer)
- Contrast nephropathy
- Vasovagal syncope
- Contrast extravasation
Correct answer: Anaphylactoid (allergy-like) reaction
Anaphylactoid reactions mimic true anaphylaxis (urticaria, bronchospasm, hypotension) but do not require prior sensitization and are not IgE-mediated.
Question 2: A patient experiences mild urticaria after CT contrast injection. What is the most appropriate immediate action?
- Administer diphenhydramine (Benadryl) and observe the patient (Correct answer)
- Immediately inject epinephrine
- Continue the scan without intervention
- Administer IV corticosteroids and discharge
Correct answer: Administer diphenhydramine (Benadryl) and observe the patient
Mild urticaria (hives only, no systemic symptoms) is treated with antihistamines and close observation while monitoring for progression to a more severe reaction.
Question 3: What is the recommended fasting time before IV contrast-enhanced CT in non-emergency patients?
- 4 hours NPO for solids (Correct answer)
- No fasting required
- 24-hour fast
- 12-hour fast
Correct answer: 4 hours NPO for solids
A 4-hour fast is recommended before contrast CT to reduce aspiration risk in the event of nausea or vomiting, while preventing dehydration.
Question 4: Which factor most significantly increases a patient's risk for a severe contrast reaction?
- History of a prior severe contrast reaction (Correct answer)
- Mild shellfish allergy
- Asthma controlled with inhalers
- Age over 65
Correct answer: History of a prior severe contrast reaction
A prior severe contrast reaction is the single strongest risk factor for a repeat severe reaction, increasing risk approximately 5-fold.
Question 5: What technique is used to time the CT acquisition to arterial contrast peak in CT angiography?
- Bolus tracking (SmartPrep) or test bolus technique (Correct answer)
- Fixed-delay scanning
- Breathing command protocol
- ECG gating
Correct answer: Bolus tracking (SmartPrep) or test bolus technique
Bolus tracking uses real-time low-dose monitoring of a target vessel; when attenuation reaches a threshold, the diagnostic scan is automatically triggered.
Question 6: Contrast extravasation during CT injection most commonly occurs at which site?
- The IV catheter insertion site in the antecubital fossa (Correct answer)
- The aorta
- The pulmonary veins
- The renal pelvis
Correct answer: The IV catheter insertion site in the antecubital fossa
Extravasation occurs when contrast leaks from a dislodged or infiltrated IV catheter into surrounding soft tissue, most often at the antecubital injection site.
Computed Tomography Test CT Contrast Media and Patient Preparation 2
What type of adverse reaction to iodinated contrast media involves an immune-mediated hypersensitivity response?