14.3 Adverse Reactions & Emergency Response

14.3 Adverse Reactions & Emergency Response

Quick Answer: When contrast goes wrong, stop the injection, assess ABCs, call for help early, and classify the reaction. Treat anaphylactoid crises as true emergencies (epinephrine pathway under protocol); treat vasovagal events with supine positioning and monitoring. Manage extravasation as a tissue injury event. Document thoroughly and escalate to a code/team for respiratory compromise, shock, or collapse.

RTR.5.8 expects competent response to adverse effects of administered substances. This section specializes the general emergency framework from Care Provider content (Chapter 3) for contrast and pharmaceutical events in the CT/fluoroscopy environment.

Reaction Classification: Mild, Moderate, Severe

Professional societies (e.g., ACR-style severity groupings used widely in practice teaching) sort acute allergic-like and physiologic reactions by clinical impact. Memorize patterns, not brand-specific trivia.

Key teaching point: a patient who is “a bit warm and metallic-tasting” after IV contrast is usually experiencing expected physiologic effect, not a graded “mild allergic reaction.” Conversely, scattered hives are mild allergic-like even if the patient is still talking comfortably—observe for progression.

Delayed reactions

Some cutaneous reactions appear hours later. Teach patients when to seek care; document and flag the record so future protocols can adjust (premedication, different agent, alternative modality).

Anaphylactoid (Allergic-Like) vs Vasovagal

Iodinated contrast reactions that look like allergy are often called allergic-like or anaphylactoid because they may not be classic IgE-mediated allergy, yet they behave clinically like anaphylaxis and are treated with the same urgency when severe.

Exam killer mistake: giving only an antihistamine and watching while a patient has stridor and hypotension—that is anaphylaxis management failure. Antihistamines help cutaneous symptoms; they do not replace epinephrine when anaphylaxis criteria are met.

Extravasation Management (Detail)

1. Stop the power injector/manual injection immediately.
2. Disconnect the tubing; attempt aspiration of residual contrast from the cannula if trained and protocol supports it; then remove the catheter as directed.
3. Mark the borders of swelling; estimate volume extravasated (programmed volume minus remaining).
4. Elevate the limb; apply cold or warm compresses according to departmental protocol (practices vary—know yours; exam items often emphasize stop, assess, notify, document rather than a single universal compress dogma).
5. Notify the radiologist/physician responsible; surgical consultation if severe pain, evolving neurovascular compromise, or very large volumes.
6. Observe for blistering, increasing pain, sensory change, or signs concerning for compartment syndrome (severe pain, tense compartment, pain on passive stretch, paresthesia, weak pulses late).
7. Document and provide aftercare instructions (what symptoms trigger ED return).
8. Incident reporting per facility quality pathway.

Small extravasations may need only observation; large-volume iodinated extravasation is never “just a bruise until proven otherwise.”

Emergency Response Steps (Contrast-Focused)

Use a repeatable sequence:

1. Recognize — cutaneous, respiratory, cardiovascular, or neurologic change after substance administration.
2. Stop the contrast/drug immediately; preserve IV access if safe (another site may be needed; do not leave a failed extravasated line as your only access plan without assessment).
3. Call for help early — radiologist, emergency response team, code blue as indicated. State location, “contrast reaction,” and severity signs.
4. Position —
   • Respiratory distress: upright if preferred and perfusion allows
   • Hypotension/shock: supine; legs elevated if not contraindicated
   • Unresponsive: recovery position if breathing and no trauma contraindications; CPR position if pulseless
5. Airway/Breathing — open airway; suction if needed; high-flow oxygen per protocol; prepare for advanced airway by the code team.
6. Circulation — pulse check; BP; CPR/AED if indicated.
7. Drugs — assist with epinephrine and other agents under order/medical directive; know cart locations before the emergency.
8. Monitor — SpO₂, BP, HR, mentation, skin; reassess every minute in evolving reactions.
9. Handover — agent name/concentration, volume given, time of start/stop, allergies, premeds, sequence of signs, treatments and response.
10. Document after stabilization.

When to call a code / emergency team

Activate full emergency response for:

• Stridor, severe wheeze, or hypoxia not rapidly improving
• Facial/tongue swelling threatening the airway
• Hypotension with allergic-like features or collapse
• Chest pain with instability, arrhythmia, or severe distress
• Seizure, unresponsiveness, or cardiac arrest
• Any situation exceeding your ability to manage with local resources

If unsure whether the event is “moderate” or “severe,” over-call rather than under-call. Teams can stand down; hypoxic brains cannot wait for perfect taxonomy.

Documentation Essentials

Chart (and incident system as required):

• Patient identifiers and exam
• Agent, lot/expiry if required by policy, concentration, volume, route, site, rate/injector settings
• Time of administration and time of onset of signs
• Full symptom list and vital signs over time
• Interventions (oxygen L/min and device, meds with dose/route/time, positioning)
• Response to treatment
• Who was notified and when
• Patient disposition (observe, transfer to ED/inpatient, discharge with instructions)
• Advice given about future contrast and medical alert updates

Good documentation protects the patient at the next visit as much as it protects the current record.

Worked Clinical Scenarios

Scenario A — Mild cutaneous reaction

Case: Two minutes after IV LOCM, a stable outpatient develops five small urticarial wheals on the chest, mild pruritus, SpO₂ 98% on room air, BP 128/78, HR 88, no respiratory symptoms.

RTR actions: Stop further contrast if more was planned; assess lungs and airway; notify radiologist/nurse pathway per protocol; observe; administer/assist antihistamine if ordered; do not discharge until clear stability criteria met; document and flag chart.

Not appropriate: Ignoring hives; giving epinephrine without indications; forcing completion of unnecessary additional boluses.

Scenario B — Anaphylactoid emergency

Case: Mid-bolus, patient clutches throat, develops diffuse hives, audible wheeze, BP 78/40, HR 130, SpO₂ 89%.

RTR actions: Stop injector; call code/emergency team and radiologist; high-flow oxygen; supine or position for perfusion/airway as team directs; assist epinephrine per protocol immediately; prepare suction and airway equipment; support CPR if arrest; full documentation after ROSC/stabilization.

Trap: Waiting to “see if hives improve alone” while hypotensive and hypoxic.

Scenario C — Vasovagal during venipuncture

Case: Anxious fasting patient becomes diaphoretic and nauseated as the tourniquet goes on; HR drops to 42; BP 88/50; pale; no hives or wheeze.

RTR actions: Abort stick if needed; supine, protect from fall; elevate legs if appropriate; loosen tight clothing; monitor until recovery; delay contrast until stable; consider rescheduling if recurrent severe vagal events; document.

Trap: Treating as anaphylaxis with epinephrine when the picture is pure bradycardic vagal without allergic features—still call for help if unstable, but recognize the pattern.

Scenario D — Large extravasation

Case: During arterial-phase injection, pressure alarm sounds; antecubital fossa rapidly swells; patient reports severe pain; ~80 mL iodinated contrast estimated extravasated.

RTR actions: Stop; assess neurovascular status; mark/elevate; notify radiologist urgently; follow extravasation protocol; arrange clinical review; document volume and instructions; incident report.

Trap: Completing venous phases through the same blown IV.

Scenario E — Post-CT delayed concern (teaching call)

Case: Patient calls the next day with widespread itch and new rash after an uneventful scan.

RTR/department actions: Advise clinical assessment pathway per policy (often ED/urgent care if progressive or systemic symptoms); ensure the reaction is entered in the medical record/allergy field for future imaging; communicate with radiology nursing/radiologist as required.

Common Exam Traps

1. Equating normal warmth with a graded allergic reaction.
2. Using antihistamine as sole therapy for anaphylactic shock.
3. Missing bradycardia as a clue to vasovagal rather than allergic-like shock.
4. Failing to stop the injection as step one.
5. Under-documenting volume and timing of extravasation.
6. Discharging a moderate reactor without observation or instructions.

Integration With Hours-on-Task Study Strategy

Contrast emergencies are low frequency and high stakes—exactly the pattern application exams love. Drill yourself with 60-second mental simulations: What do I say on the emergency phone? Where is epinephrine? What vitals do I recheck? Pair this section with Chapter 3 medical emergencies and Chapter 12 GI agent selection so RTR.3/4/5 items feel like one clinical story rather than three silos.

When uncertain in real practice or on a scenario item: protect airway and perfusion, call for help early, stop the offending agent, and work inside protocol—that sequence is almost always defensible.