Friday, August 26, 2016

Anaphylaxis Management

Today at noon rounds we discussed anaphylaxis. Anaphylaxis is a serious allergic reaction that is rapid in onset and may cause death. Here are some clinical pearls on anaphylaxis.

1.       Have anaphylaxis on your differential diagnosis for an acutely sick patient. If you don’t think about it you may miss it!
2.       Anaphylaxis can mimic other conditions and present differently, which is why it is important to think about it (Internal thought bubble: “Could this acutely sick patient have anaphylaxis?”)

Signs/symptoms of anaphylaxis can include:

-          Symptoms/signs occur rapidly (minutes to hours) after exposure to a known or likely allergen
-          Skin and mucosal symptoms and signs (ie. hives, pruritus, flushing, swollen lips, swollen tongue, angioedema) *This is an important clue to look for as it is present in up to 90% of anaphylactic episodes
-          Respiratory compromise (i.e. nasal congestion, laryngeal itching and “tightness” in the throat, hoarseness, stridor, dyspnea, wheeze, bronchospasm, hypoxemia)
-          Cardiovascular compromise (could also present with hypotension syncope, incontinence, dizziness, tachycardia)
-          Gastrointestinal (i.e. crampy abdominal pain, nausea, vomiting, diarrhea)

Priorities for the management of anaphylaxis:

1.       ABCs (airway, breathing, circulation) CALL FOR HELP!
o   Airway: early intubation is often indicated and one needs to be alert for signs of airway compromise. Call for help from an airway expert (respiratory therapy and anesthesia) early!
o   Breathing: Supplemental oxygen
o   Circulation: IV fluids (normal saline bolus)
o   IV access (two large bore IV catheters) and monitors (cardiac monitors, continuous oxygen saturation monitoring and frequent blood pressure monitoring)
2.       Epinephrine
o   Prompt recognition of anaphylaxis and administration of epinephrine is key!
o   Studies have shown failure or delay in administration of epinephrine may increase the risk of death1
o   The first choice is Epinephrine IM (intramuscular) 1:1000 concentration (1 mg/mL): give epinephrine 0.3-0.5 mg intramuscularly in mid-outer thigh, maximum 3 doses
o   If intramuscular epinephrine is not available quickly, give epinephrine IV. Epinephrine IV (intravascular) 1:10,000 concentration (0.1 mg/mL): give epinephrine 0.1 mg IV slowly over 1-3 minutes. Note that the concentration of epinephrine that is given intravascularly and is often on code carts is different than the concentration of epinephrine that is given intramuscularly. This can cause dosing errors and cardiovascular complications due to overdosing. The 10mL prefilled syringes of epinephrine used in cardiac arrest on the code carts are 1mg of epinephrine in a 10mL prefilled syringe. Therefore, to give 0.1mg for anaphylaxis, you only give 1/10th (1mL) of the prefilled syringe that is given in the ACLS algorithms!  Usually a response is observed after a single dose, giving you time to prepare an epinephrine infusion. If there is an inadequate response to the first dose, a second dose can be given.
o   If there is an inadequate response to initial IM or IV epinephrine, you can start a continuous epinephrine infusion, beginning with epinephrine IV infusion 0.1 mcg/kg/minute
o   If on a beta-blocker and no response to epinephrine, you can give glucagon 1-5mg IV over 5 minutes then an infusion at 5-15 mcg/min  


3.       Removal of inciting antigen (i.e. stop infusion of a suspect medication)
4.       Adjuncts:
o   Glucocorticoids: Methylprednisolone (Solumedrol) 125 mg IV
o   Ventolin PRN
o   Anti-histamines:
                                                               i.      Diphenhydramine (Benadryl) 50 mg IV
                                                             ii.      Ranitidine 50 mg IV

1.       Dhami S et al. Management of anaphylaxis: a systematic review. Allergy. 2014;69(2):168-75. 

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