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6Emergency Imaging

Emergency Premedication (in Decreasing Order of Eectiveness)

This premedication consists of methylpred-nisolone sodium succinate (Solu-Medrol) 40 mg or hydrocortisone sodium succinate (Solu-Cortef) 200 mg intravenously every 4 hours until contrast study required plus diphenhydramine 50 mg IV 1 hour prior to contrast injection.

Management of Idiosyncratic Reactions

Epinephrine is contraindicated in severe heart disease.

Mild Reaction

• Most require no specific treatment• Discontinue injection, maintain IV access

• Monitor, reassure patient

• Diphenhydramine 25–50 mg PO/IV

IV Contrast Delivery and

Maximum Flow Rates

Many CT examinations require rapid injec-tion of contrast material for optimal vessel opacification. Small peripheral IV catheters and some central venous catheters cannot be reliably used for rapid injection. Exam-ples of various catheters and their maxi-mum flow rates are listed here (Table 1.3).

Idiosyncratic/Anaphylactoid Reaction to IV Contrast Material

• 0.6% incidence of all reactions (nonionic)

• 0.01–0.02% incidence of severe reactions (nonionic)

• ~ 1/170,000 fatality attributed to contrast injection

Adverse Reaction Classication

(Table 1.4)

Risk Factors for Idiosyncratic Reaction and Indications for Premedication

• Prior moderate or severe reaction to intravenous contrast material• Asthma with active wheezing

• Asthma with history of event requiring intubation in past 90 days

• Any prior life-threatening allergic reaction

Mild or moderate reactions to other aller-gens (seafood, medications), mild urticarial reactions to contrast material, and mild to moderate asthma do not require premedi-cation with steroids.

Elective Premedication

Recommended premedication consists of prednisone, 50 mg by mouth at 13 hours, 7 hours, and 1 hour before contrast media in-jection, plus diphenhydramine (Benadryl), 50 mg intravenously, intramuscularly, or by mouth 1 hour before contrast medium.

If the patient is unable to take oral medication, 200 mg of hydrocortisone in-travenously may be substituted for oral prednisone.

Table 1.3 IV contrast delivery and maximum ow rates

Peripheral IV catheter

20-gaugeup to 5 mL/sec

22-gauge

up to 3 mL/sec

24-gauge

up to 1.5 mL/sec

Triple-lumen central catheter1 mL/sec

PICC line1 mL/sec

Power PICC

Rate indicated on hub

Introducer sheathup to 5 mL/sec

Broviac/Hickman1 mL/sec

Table 1.4 Adverse reaction classication

MildTransient, self-limited, and not life-threatening: nausea, cough, headache, dizziness, itching, chills, ushing, chills, sweating, rash, nasal stuness

ModerateSystemic and more severe mild reactions: pulse change, hypotension, hypertension, dyspnea/wheezing, urticaria, bronchospasm, laryngospasm

SeverePotentially life-threatening:

Unresponsiveness, convulsions, anaphylaxis, cardiopulmonary arrest, symptomatic arrhythmia