A 25-year-old man comes to the emergency department after being stung by a wasp on his right arm 30 minutes ago. He reports generalized itching and mild local pain. He has no other medical conditions. Temperature is 36.7 C (98.1 F), blood pressure is 122/81 mm Hg, pulse is 108/min, and respirations are 22/min. Pulse oximetry is 94% on room air. Examination shows a 2 × 2 cm, erythematous, elevated, warm, and mildly tender area on the right arm. Multiple wheals are visible on the trunk and extremities. There is no tongue swelling or stridor. Bilateral wheezes are present on lung auscultation. The remainder of the examination is normal. Which of the following is the most appropriate next step in management of this patient?

Question

A 25-year-old man comes to the emergency department after being stung by a wasp on his right arm 30 minutes ago.  He reports generalized itching and mild local pain.  He has no other medical conditions.  Temperature is 36.7 C (98.1 F), blood pressure is 122/81 mm Hg, pulse is 108/min, and respirations are 22/min.  Pulse oximetry is 94% on room air.  Examination shows a 2 × 2 cm, erythematous, elevated, warm, and mildly tender area on the right arm.  Multiple wheals are visible on the trunk and extremities.  There is no tongue swelling or stridor.  Bilateral wheezes are present on lung auscultation.  The remainder of the examination is normal.  Which of the following is the most appropriate next step in management of this patient?

Quizplus · Accepted Answer

Explanation: 11ec2b69_bdd0_a2d1_8f63_6dfb889e67f0_MD0005_00 This patient developed sudden-onset pruritus, urticaria (ie, wheals on the trunk and extremities), and wheezing following a wasp sting. This presentation is consistent with anaphylaxis, a severe IgE-mediated type I hypersensitivity reaction that may be diagnosed when acute allergic symptoms (eg, rash, wheezing) are present in ≥2 systems (eg, skin, respiratory) after allergen exposure (eg, wasp sting). Patients with normal blood pressure, like this one, can still experience anaphylaxis; hypotension is not required to make the diagnosis, although it is often present. diagnosed Even when initial symptoms are less severe (ie, no shock or respiratory distress), intramuscular (IM) epinephrine should be administered as soon as anaphylaxis is diagnosed because symptom progression can be unpredictable, rapid, and varied. Early administration of IM epinephrine is the most important step in management of anaphylaxis due to its immediate and broad systemic effects (eg, bronchodilation, decreased systemic release of inflammatory mediators, vasoconstriction). Failure to administer epinephrine early (vs after onset of hypotension) can result in cardiovascular collapse and is associated with a higher incidence of fatalities. management of anaphylaxis Patients should be educated about epinephrine autoinjector administration and the importance of carrying this potentially lifesaving medication at all times. In addition, they should be referred to an allergist for venom immunotherapy, which can reduce the risk for insect sting anaphylaxis from 35%-60% to <5%. (Choice A) Inhaled albuterol (a beta-2 agonist) may eventually be administered to improve this patient's bronchoconstriction (eg, wheezing). Unlike epinephrine, however, it does not address the patient's other anaphylactic symptoms (eg, pruritus, urticaria) or prevent potential further deterioration and shock. (Choices C and E) Intravenous diphenhydramine and oral hydroxyzine are antihistamines that can relieve pruritus and urticaria. Although they are appropriate as first-line therapy in local allergic reactions, they do not relieve airway obstruction or prevent shock in anaphylaxis. Therefore, they should be used only as adjuvant therapies following first-line treatment with IM epinephrine. (Choice D) Glucocorticoids (eg, intravenous methylprednisolone) may be administered as adjunct therapy due to their anti-inflammatory effect; however, they are not an appropriate first step because of their delayed onset of action. Educational objective: The diagnosis of anaphylaxis can be made based on acute allergic symptoms in ≥2 systems after allergen exposure. Hypotension is not required to make the diagnosis. Intramuscular epinephrine is first-line treatment, and early administration improves outcomes. References: 2012 update: World Allergy Organization guidelines for the assessment and management of anaphylaxis. (http://www.ncbi.nlm.nih.gov/pubmed/22744267) Epinephrine absorption in adults: intramuscular versus subcutaneous injection. (http://www.ncbi.nlm.nih.gov/pubmed/11692118) Venom immunotherapy for preventing allergic reactions to insect stings. (http://www.ncbi.nlm.nih.gov/pubmed/23076950)

A 25-Year-Old Man Comes to the Emergency Department After Being