Emergency Imaging. Alexander B. Baxter

      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