Anaphylaxis: Symptoms and Presentation

• Anaphylaxis is a serious, life-threatening allergic reaction.
• Common triggers include foods, insect stings, and medications.

Presentation

Dermatologic/mucosa:

• Eyes: Periorbital swelling, erythema/itching
• Oral: Angioedema or pruritus of tongue and lips
• Skin: Urticaria, pruritus/flushing, angioedema

Cardiovascular (early):

• Tachycardia
• Diaphoresis
• Hypotension
• Delayed capillary refill
• Chest pain

Cardiovascular (late):

• Bradycardia
• Shock
• ST depression & T-wave inversion
• Cyanosis
• Cardiac arrest

Respiratory (lower airway):

• Bronchospasm, wheezing
• Chest tightness
• Tachypnea
• Decreased PEF
• Cyanosis
• Respiratory collapse

Respiratory (upper airway):

• Throat feels constricted
• Dry cough
• Trouble breathing, swallowing or speaking
• Changes in voice
• Stridor

Gastrointestinal:

• Nausea
• Vomiting
• Diarrhea
• Abdominal cramps

Neurologic:

• Throbbing headache
• Dizziness
• Lightheaded
• Confusion
• LOC
• Aura of impending doom, anxiety

Diagnosis of Anaphylaxis

• Primarily based on a detailed history and clinical symptoms.
• History should include all exposures and events prior to symptom onset (ingestion of drugs, ethanol, acute infection, stress, disruption of routine, premenstrual status).
• Sudden onset within minutes to hours after allergen exposure.
• Rapid symptom progression.
• Symptoms typically involve two or more body systems.

Clinical Criteria for Diagnosis

• Anaphylaxis is probable when any 1 of 3 criteria is met:
  • Acute illness with skin/mucosal involvement AND respiratory symptoms OR hypotension/LOC.
  • Two or more symptoms after likely exposure to allergen (skin/mucosa, respiratory compromise, hypotension, GI symptoms).
  • Reduced BP rapidly after known allergen exposure: SBP < 90 mm Hg in adults, or low for age in children.

Differential Diagnoses

• Any condition causing sudden patient collapse:
  • Myocardial Infarction (MI)
  • Pulmonary embolism
  • Hypoglycemia
  • Seizure
  • Vasovagal syncope
  • Panic attack
  • Acute asthma exacerbation
  • Individual allergic reaction symptoms without meeting anaphylaxis criteria.

Lab Tests

• Anaphylaxis diagnosis relies on clinical symptoms as lab tests aren't usually helpful.
• Allergen skin/serologic (serum IgE) testing detects allergen sensitivity, but does not predict anaphylaxis.
• Allergy testing is helpful if the anaphylaxis trigger is unknown, to identify and avoid it in the future.

Treatment: Non-Pharmacologic

• Remove trigger if possible(stop the drug if that is the cause).
• Rapidly assess circulation, airway, and breathing.
• Assess mental status, estimate weight.
• Call for help or have someone call 911.
• Place the patient supine with legs elevated or lying on their side.
• Inject epinephrine (pharmacologic treatment).
• Be prepared to perform CPR.
• Monitor BP, HR, respiratory status, and oxygenation.
• Provide supplemental oxygen or IV fluids if needed.

Treatment: Pharmacologic

• Intramuscular epinephrine is the first-line treatment.
  • Adults: 0.3-0.5 mg IM x 1 dose; repeat every 5-15 minutes if needed.
  • Infants/children: 0.01 mg/kg IM x 1 dose; repeat every 5-15 minutes if needed.
• Administer into the anterolateral thigh muscle (vastus lateralis).
• Epinephrine increases vasoconstriction, decreases mucosal edema, and increases inotropy and chronotropy.
• Side effects include anxiety, restlessness, headache, dizziness, palpitations, pallor, and tremor, which are similar to the "fight-or-flight" response.
• Autoinjector devices like EpiPens (children 0.15 mg, adults 0.3 mg) can be used.

Contraindications to Epinephrine

• There are no absolute contraindications to epinephrine.
• Some patients may have a higher risk for adverse effects:
  • Cardiovascular disease (uncontrolled BP, aortic aneurysm)
  • MAO inhibitors or TCA prolong epinephrine duration
  • Pre-existing conditions like hyperthyroidism or recent intracranial surgery
  • Stimulants like methylphenidate (for ADHD) or cocaine abuse.
• Delayed administration leads to poorer outcomes.

Other Medications given for Anaphylaxis

• H1 antihistamines (Benadryl 25-50 mg)
  • May reduce skin symptoms
• Corticosteroids (methylprednisolone 1-2 mg/kg/day)
  • May prevent biphasic reaction
• Bronchodilators (Albuterol)
  • For patients with asthma or RAD who do not respond to epinephrine

Biphasic Reaction

• Symptoms recur within 1-72 hours after initial symptoms resolve, without further trigger exposure.
• Usually occurs within 8-10 hours.
• Reported in 4.5-23% of anaphylactic episodes.
• Monitor the patient in the hospital.

Patient Education and Follow-up

• Long-term management is required as patient are at increased risk for future episodes.
• Development and implementation of anaphylaxis emergency action plan.
• Educate on Epipen use.
• Usage of a medication identification bracelet.
• Identification and avoidance of anaphylaxis triggers.
• Management of concurrent diseases.
• Follow-up with an allergy/immunology specialist.

Geriatric Considerations

• Increased risk for anaphylaxis due to increased age and additional medications (e.g., beta blockers).
• Increased risk for adverse effects from epinephrine due to underlying conditions, particularly respiratory or cardiovascular.
• Older adults account for most fatal anaphylaxis cases due to medication/drug allergies.