Urticaria, Emergency Medicine

Basics

Description

Cutaneous mast and basophil cellular release of inflammatory mediators, primarily histamine:
- Increased vascular permeability and pruritus
Edema of the epidermis as well as the upper and middle dermis:
- More common in children and young adults
- More common in women
- More common in the atopic patient
40% of patients with urticaria will have a component of angioedema:
- Affects deeper subdermal and/or submucosal sites

Urticaria is often the result of reactions to foods and infections
Swelling of distal extremities and acrocyanosis may be prominent in infants
Bullae may form in the center of the wheal, especially on legs and buttocks

Etiology

Acute: ‚
Presumptive trigger may be found, but majority of cases are idiopathic ‚
Course of <6 wk ‚

Drugs:
- Few have recurrent urticaria on later antigenic challenge
Foods or additives
Herbal medications, vaccines, opiates
Insect bites and stings
Connective tissue diseases
Endocrine disorders, especially Hashimotos thyroiditis
Cancers, especially lymphoproliferative
Hormonal imbalance, pregnancy, menstrual cycle, exogenous estrogens
Infections:
- Viral (including hepatitis, HIV)
- Viral URI most common associated infection
- Bacterial
- Fungal
- Parasitic
Inhaled or contact allergen
Emotional stress
Physical urticaria " ”>20 identified types, including:
- Dermographism:
  - Most common physical form
  - Reaction to skin pressure
  - Linear wheals under tight clothing
  - Areas scratched with a firm object
- Cholinergic:
  - Monomorphic wheals 2 " “3 mm
  - Bright red flare and intense pruritus
- A response to elevated core temperature:
  - Hot bath
  - Fever
  - Exercise
- Other rare forms:
  - Cold-induced (may be fatal in cold immersions)
  - Sun exposure
  - Aquagenic

Chronic: ‚
Course of >6 wk ‚

75% idiopathic in nature
Autoimmune disease spectrum
Immune complex " “induced
Often an unrecognized recurring physical urticaria
May be due to occult or subclinical infection or systemic disease

Diagnosis

Signs and Symptoms

History

Prior history
Familial history
Alleviating and/or aggravating factors
Time course of current presentation:
- Often helpful to circle lesions to document their duration
- Fever and systemic symptoms
- Arthralgias and myalgias
- Weight loss and lymphadenopathy
- Hypotension, flushing, headache
- Swelling of mucosal sites
- Respiratory distress or airway symptoms:
  - May be part of an anaphylactic reaction

Physical Exam

Focus on signs of systemic allergic reaction or infection
Airway " ”angioedema, airway compromise, inability to handle secretions, abnormal phonation, stridor
Breathing " ”wheezing
Circulation " ”systemic signs of anaphylaxis, such as hypotension
Abdomen " ”hepatosplenomegaly, pregnancy
Dermal " ”associated edema, associated petechiae, or purpura:
- Generalized, transient, pruritic, well-circumscribed skin eruptions
- May include palms or soles
- May include bullae or purpuric lesions
- Lesions are of various sizes and shapes, haphazard in distribution, and may become confluent
- Wheals usually resolve in 3 " “4 hr
- New lesions evolve as old ones resolve
Lymphadenopathy
Dermographism:
- Scratch skin with a tongue blade; observe for linear wheal
Cholinergic:
- Exercise challenge to raise core temperature or induce sweating
Expose to sunlight
Cold-induced:
- Place an ice cube on skin for 5 min
Aquagenic:
- Apply tap water at differing temperatures
Significant mucosal edema:
- Suspect angioedema
- Severe reaction with hypotension
- Suspect anaphylaxis
Prolonged, painful, or nonblanching lesions:
- Suspect urticarial vasculitis

Essential Workup

Complete history and physical exam
Lesion appearance, location, timing, duration
Identify as acute vs. chronic time-course
Associated symptoms, triggers
Coexisting diseases, allergies, medications
Evaluate for sources of infection and signs of systemic diseases

Diagnosis Tests & Interpretation

Lab

Acute urticaria: No labs needed
Chronic urticaria:
- Evaluate for infection or systemic disease:
  - CBC with differential, ESR, and/or CRP
  - Thyroid-stimulating hormone and thyroid functions
  - Urinalysis, liver function tests
Skin biopsy if urticarial vasculitis suspected (not done in ED)

Imaging

Acute cases: Not needed
Chronic cases:
- Directed at search for occult infection

Diagnostic Procedures/Surgery
Skin biopsy " ”for chronic urticaria or urticarial vasculitis ‚

Differential Diagnosis

Angioedema:
- Can be life-threatening
- May have component of abdominal symptoms
- Hereditary or acquired
Cutaneous vasculitis
Serum sickness
Erythema multiforme
Bullous pemphigoid
Juvenile rheumatoid arthritis
Erythema marginatum
Dermatitis herpetiformis
Systemic mastocytosis
Henoch " “Schonlein purpura

Treatment

Pre-Hospital

Cautions:
- Systemic allergic reactions can rapidly progress if not treated with early epinephrine
Severe reaction:
- Manage airway, oxygen
- IM epinephrine
- Parenteral or inhaled Ž ²-agonist for bronchospasm
- IV crystalloid and vasopressors as needed

Initial Stabilization/Therapy

Remove offending agent if possible ‚

Ed Treatment/Procedures

Largely symptomatic except in severe reactions
Treatment aimed at stimulus, effector cells, inflammatory mediators, and target receptors
Ž ²-Agonist (parenteral or inhaled):
- Severe hives, angioedema, systemic features
H1-receptor antagonist (1st or 2nd generation):
- Mainstay of treatment
H2-receptor antagonist:
- May be beneficial as adjunct to H1 blocker when no response to H1 blocker alone
Corticosteroid (oral):
- Severe or refractory cases
Avoid NSAIDs and opiates:
- May exacerbate condition
Concurrent use of ketoconazole or macrolides alters hepatic metabolism of antihistamine; use with caution

Medication

Ž ²-Agonists:
- Epinephrine (1:1,000 solution): 0.1 " “0.5 mg IM q10 " “15min PRN (peds: 0.01 mg/kg, IM [max. single dose not to exceed 0.3 mg] q15min PRN)
- IV epinephrine 0.1 " “0.25 mg (1:10,000 sol) IV over 5 " “10 min q5 " “15min then 1 " “4 Ž ¼g/min IV ONLY if anaphylactic shock
- Albuterol (0.5% solution): 0.5 mL nebulized q20min PRN (peds: 0.01 " “0.05 mL/kg per dose [max. 0.5 mL/dose] nebulized q20min PRN bronchospasm)
- Terbutaline: 0.25 mg SC q15 " “30min PRN (max. 0.5 mg q4h); (peds: <12 yr old; 0.005 " “0.01 mg/kg [max. 0.4 mg/dose] SC q15 " “20min ƒ — 3 PRN bronchospasm)
H1-receptor antagonist (1st generation " ”lipophilic and sedating)
- Diphenhydramine: 25 " “50 mg PO, IV, or IM q6h (peds: 1 mg/kg q6h [max. 300 mg/24 h])
- Hydroxyzine: 25 " “50 mg PO or IM q6h (peds: 2 mg/kg/24 h PO div. q8h or 0.5 " “1 mg/kg IM q4 " “6h PRN)
H1-receptor antagonist (2nd generation " ”less sedating and preferred):
- Cetirizine: Adult and peds ≥6 yr old: 5 " “10 mg PO QD (peds 2 " “6 yr old: 2.5 mg QD to BID)
- Loratadine: 10 mg PO BID (peds 2 " “6 yr old: 5 mg PO QD
- Fexofenadine: 60 mg PO BID or 180 mg PO QD (peds 6 " “12 yr old: 30 mg PO BID)
H2-receptor antagonist (suggested dosage):
- Famotidine: 20 mg IV q12h or 20 " “40 mg PO QHS (peds: 1 mg/kg/d div. QID [max. 40 mg/24 h])
- Ranitidine: 150 mg PO BID (peds: Neonate: 2 " “4 mg/kg/24 h PO div. q8 " “12h or 2 mg/kg/24 h IV div. q6 " “8h; infants and children: 4 " “5 mg/kg/24 h PO div. q8 " “12h or 2 " “4 mg/kg/24 h IV or IM div. q6 " “8h)
Corticosteroid:
- Methylprednisolone: 125 mg IV (peds: Start at 2 mg/kg ƒ — 1)
- Prednisolone: 50 mg PO QD for 3 days (peds: 0.5 " “2 mg/kg/24 h [max. 80 mg/24 h] div. QD to BID for 3 " “5 days)
- Prednisone: 40 mg PO QD or 20 mg PO BID for 3 " “5 days (peds: 1 " “2 mg/kg/24 h [max. 80 mg/24 h] div. QD to BID for 3 " “5 days)
Antileukotrienes:
- Montelukast: 10 mg PO QD
- Zafirlukast: 20 mg PO BID

First Line

H1-receptor antagonist, 2nd generation
Corticosteroids
Ž ²-Agonists:
- Albuterol if bronchospasm present
- Epinephrine for severe or systemic signs

Second Line

Antileukotrienes
H1-receptor antagonist, 1st generation
H2-receptor antagonist, data weak

Follow-Up

Disposition

Admission Criteria

Systemic allergic reaction with:
- Respiratory distress or failure
- Refractory hypotension or shock
Severe case with dysfunction of health-related quality of life
Other comorbidities

Discharge Criteria

Normal vitals
Absence of other condition requiring admission
Adequate ability of caregivers at home to monitor for further exacerbations

Followup Recommendations

Follow with PCP, especially if lasting >6 wk ‚

Pearls and Pitfalls

If severe presentation, there is often a biphasic course. Rebound may occur in 4 " “6 hr
Chronic urticaria often has a systemic cause

Additional Reading

Kropfl ‚ L, Mauer ‚ M, Zuberbier ‚ T. Treatment strategies in urticaria. Expert Opin. Pharmacother. 2010;11:1445 " “1450.
Nichols ‚ K, Cook-Bolden ‚ F. Allergic skin disease: Major highlights and recent advances. Med Clin N Am. 2009;93:1211 " “1224.
Ricci ‚ G, Giannetti ‚ A, Belotti ‚ T, et al. Allergy is not the main trigger of urticaria in children referred to the emergency room. J Eur Acad Dermatol Venereol. 2010;24:1347 " “1348.
Wolfson ‚ AB, Hendey ‚ GW, Ling ‚ LJ, et al. (eds) Harwood-Nuss ' Clinical Practice of Emergency Medicine. 5th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2010.
Zuberbier ‚ T. A summary of the new international EAACI/GA(2)LEN/EDF/WAO guidelines in urticaria. WAO J. 2012;5(suppl 1):S1 " “S5.
Zuberbier ‚ T, Asero ‚ R, Bindslev-Jensen ‚ C, et. al. EAACI/GA2LEN/EDF/WAO guideline: definition, classification, and diagnosis of urticaria. Allergy. 2009;64:1417 " “1426.

Codes

ICD9

708.0 Allergic urticaria
708.1 Idiopathic urticaria
708.9 Unspecified urticaria
708.8 Other specified urticaria
995.1 Angioneurotic edema, not elsewhere classified

ICD10

L50.0 Allergic urticaria
L50.1 Idiopathic urticaria
L50.9 Urticaria, unspecified
L50.6 Contact urticaria
T78.3XXA Angioneurotic edema, initial encounter

SNOMED

126485001 urticaria (disorder)
40178009 Allergic urticaria (disorder)
42265009 Idiopathic urticaria (disorder)
19364004 contact urticaria (disorder)
41291007 angioedema (disorder)

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