842. Pitfall in diagnosing anaphylaxis in patients taking antihistamines / Anaphylaxis ddx: acute respiratory compromise ddx, cutaneous symptoms ddx // Epi dose in anaphylaxis

February 4th, 2009
by reuben in allergy

842. Pitfall in diagnosing anaphylaxis in patients taking antihistamines / Anaphylaxis ddx: acute respiratory compromise ddx, cutaneous symptoms ddx // Epi dose in anaphylaxis

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Responses to “842. Pitfall in diagnosing anaphylaxis in patients taking antihistamines / Anaphylaxis ddx: acute respiratory compromise ddx, cutaneous symptoms ddx // Epi dose in anaphylaxis”

  1. Intramuscular epinephrine is dosed at 0.3 to 0.5 mg of 1:1000 (1 mg in 1 mL) solution, which is 0.3 to 0.5 mL. This may be repeated several minutes later as needed. Once the second intramuscular dose of epinephrine is given, preparations are made to give intravenous epinephrine. Small boluses of either “crash cart epi,” which is 1:10,000 concentration (1 mg in 10 mL) or other dilute epinephrine solutions are acceptable, however we recommend the immediate initiation of a continuous epinephrine infusion in patients requiring more than 2 intramuscular treatments. A variety of techniques for preparing an epinephrine drip are described; one easy approach is to add 1 mg of epinephrine (from either the 1:1000 vial or 1:10,000 syringe) to a liter of normal saline, which results in a 1 mcg/mL solution. This may be formally infused using a pump at 2-10 mcg/min; 2 mcg/min is 120 mL/hour of this preparation. If there is a delay in setting up a pump, approximately 20 drops are equivalent to 1 mL, therefore the bag can be hung and manually titrated, starting at 1 drop per second, which is 3 mcg/min. [from anaphylaxis issue of Emergency Medicine Practice Guidelines Update]

    Consider vasopressin 5 mg IV in epinephrine-resistent anaphylaxis, especially if patient on beta blockers.

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