What is the immediate treatment for anaphylaxis in a primary care setting?

Treatment of Anaphylaxis in Primary Care Setting

Immediately administer intramuscular epinephrine 0.01 mg/kg (maximum 0.5 mg for adults, 0.3 mg for prepubertal children) into the mid-outer thigh (vastus lateralis) as soon as anaphylaxis is recognized—this is the only first-line, life-saving intervention. 1

Immediate Recognition and Action

Call for Help First

• Activate emergency medical services (911) immediately when anaphylaxis is suspected 1
• In primary care settings, call for a resuscitation team while simultaneously treating 1
• Do not delay epinephrine administration while waiting for help 1

Recognize Anaphylaxis Clinically

Anaphylaxis involves sudden onset (minutes to hours) after allergen exposure with: 1

• Respiratory compromise: dyspnea, wheeze, stridor, throat tightness, hoarseness 1
• Cardiovascular symptoms: hypotension, tachycardia, dizziness, syncope, collapse 1
• Skin/mucosal involvement: urticaria, angioedema, flushing, lip/tongue swelling 1
• Gastrointestinal symptoms: crampy abdominal pain, persistent vomiting, diarrhea 1

Critical pitfall: Do not wait for all symptoms to be present—typically only a few symptoms manifest, and they can differ between episodes in the same patient. 1

First-Line Treatment: Epinephrine Administration

Dosing and Route

• Adults and adolescents >50 kg: 0.3-0.5 mg intramuscular (1:1000 concentration) 1, 2
• Prepubertal children: 0.01 mg/kg intramuscular, maximum 0.3 mg 1
• Children 25-30 kg: 0.15 mg via autoinjector 1
• Children >30 kg: 0.3 mg via autoinjector 1

Injection Technique

• Inject into the mid-outer thigh (vastus lateralis muscle) for optimal absorption 1
• Can inject through clothing if necessary, but avoid seams, pockets, or obstructions 3
• Use autoinjector if available to minimize errors and expedite delivery, especially if staff experience is limited 1

Repeat Dosing

• Administer a second dose after 5-15 minutes if: 1
  • Inadequate response to initial dose
  • Symptoms persist or worsen
  • Severe or rapidly progressive anaphylaxis
• Between 6-28% of patients require a second epinephrine dose 1, 4
• A third dose is rarely needed but may be administered by healthcare professionals with additional interventions 1

Critical warning: Delayed epinephrine administration is the single most important factor associated with fatal anaphylaxis. 1, 5 There are no absolute contraindications to epinephrine in anaphylaxis, including cardiac disease, age, or frailty. 1

Patient Positioning

• Place patient supine (on back) with lower extremities elevated 1
• If respiratory distress or vomiting present, position for comfort 1
• Never allow the patient to stand, walk, or run—this can precipitate cardiovascular collapse 1

Adjunctive Treatments (Only AFTER Epinephrine)

Secondary Interventions

These should never replace or delay epinephrine: 1

• Supplemental oxygen: for patients with respiratory symptoms 1
• IV fluid resuscitation: large volumes for hypotension or incomplete response to epinephrine 1
• Albuterol nebulizer (1.5 mL child, 3 mL adult) or MDI (4-8 puffs child, 8 puffs adult): for bronchospasm 1

Medications with Limited Acute Benefit

• H1 antihistamines (diphenhydramine 1-2 mg/kg, max 50 mg): address only cutaneous symptoms, not life-threatening manifestations 1
• H2 antihistamines: no high-quality evidence supports their use in acute anaphylaxis 1
• Glucocorticoids: have NO role in acute treatment due to slow onset of action and do NOT prevent biphasic reactions 1

Critical pitfall: Using antihistamines instead of epinephrine as first-line treatment is dangerous and associated with increased mortality. 5

Observation and Transfer

Monitoring Duration

• All patients must be transferred to an emergency department for observation, preferably by EMS vehicle 1
• Observe for 4-6 hours minimum after successful treatment 1
• Prolonged observation or admission warranted for: 1
  • Severe or refractory symptoms
  • Required multiple epinephrine doses
  • History of biphasic reactions

Biphasic Anaphylaxis Risk

• Occurs in 10.3% of cases, with symptoms recurring up to 72 hours later (mean 11 hours) 1
• Risk factors include severe initial reaction and requirement of >1 epinephrine dose (odds ratio 4.82) 1
• Early epinephrine administration may reduce biphasic reaction risk 1

Discharge Planning

Before discharge from emergency care, ensure: 1

• Two epinephrine autoinjectors prescribed with proper training on use 1
• Written anaphylaxis emergency action plan provided 1
• Referral to allergist for evaluation 1
• Plan for monitoring autoinjector expiration dates 1

High-Risk Populations

Patients at increased risk for severe/fatal anaphylaxis: 1

• Adolescents and young adults 1
• Coexisting asthma, especially poorly controlled 1
• Previous history of anaphylaxis 1
• Peanut/tree nut allergies 1
• Mast cell disorders 6

These patients require epinephrine autoinjector prescriptions and heightened vigilance. 1