Anaphylaxis

Essentials

• AdrenalineAdrenaline (Epinephrine) for the Treatment of Anaphylaxis with and Without Shock should be given as soon as possible intramuscularly in reactions suspected to be anaphylactic. Do not hesitate with the administration of adrenaline.
  • Intramuscular injection is the primary route of administration. For patients in shock the drug may be administered intravenously.
• All patients who have experienced a severe anaphylactic reaction are given a preloaded adrenaline syringe to take home, as well as instructions on its use.
• Immediate readiness to treat anaphylactic reactions (adrenaline available) should be available in locations where vaccinations, desensitization therapy, allergy tests or radiographic examinations with contrast medium are carried out.

Causative agents and predisposing factors

• In theory, any food (or other agent) can trigger anaphylaxis.
• Foods
  • Nuts (tree nuts and peanuts), fish, shellfish, celery, kiwi, egg, milk
• Drugs
  • Antimicrobial drugs (especially penicillins, sulpha)
  • Analgesics (opioids, NSAIDs, ASA)
  • Biological drugs, especially omalizumab
• Vaccines, blood products
• Parenterally administered proteins (e.g. gamma globulin, enzyme preparations used in cancer and deficiency diseases)
• Insect stings Insect Stings and Bites
  • Wasp, bee, mosquito
• Adder bite: see Adder (Vipera Berus) Bite
• Radiographic contrast media, blood products, allergenic products used in examinations and treatment
• Natural rubber (latex) Latex Allergy
  • Gloves, catheters, condoms, balloons
• Physical exercise (eating wheat followed by physical exercise as a rare phenomenon), shaking, cold
• Medicines used by the patient may worsen the symptoms or affect the treatment.
  • Beta blockers reduce the effect of adrenaline.
  • ACE inhibitors may worsen the anaphylactic reaction, especially in insect sting allergy.
  • MAO inhibitors and tricyclic antidepressants may strengthen the effect of adrenaline.

Symptoms

• The more rapidly the symptoms start and progress, the more severe is the reaction.
• First symptoms
  • Erythema, burning of the skin, stinging or itching
  • Tachycardia
  • A feeling of thickness in the pharynx and chest, coughing
  • Possibly nausea and vomiting
• Secondary symptoms
  • Swelling of the skin (especially the eyelids and lips), swelling of the mucous membranes (angio-oedema)
  • Urticaria
  • Laryngeal oedema, hoarseness, wheezing, bouts of coughing
  • Abdominal pain, nausea, vomiting, diarrhoea
  • Hypotension, sweating, paleness
  • In severe cases laryngeal spasm, shock, respiratory and cardiac arrest

Differential diagnosis

• Acute asthma attack
  • No skin symptoms
  • Blood pressure normal or elevated
  • Often develops over several days.
• Fainting
  • No skin or respiratory symptoms
  • Bradycardia
• Acquired or hereditary angioneurotic oedema (HAE) Hereditary Angioedema (HAE) and ACE Inhibitor-Induced Angioedema
  • No urticaria
  • Adrenaline is only weakly effective.
• Other shock state, pulmonary embolism, aspiration or airway obstruction
  • In recurrent conditions that remain unexplained, determination of serum tryptase concentration may be helpful in differential diagnostics.
  • In anaphylaxis, the tryptase concentration is increased for a few hours.
  • However, the patient must be treated immediately according to the symptoms without waiting for the laboratory result.

Management

• Stop the administration of the possibly causative agent immediately.

1. AdrenalineAdrenaline (Epinephrine) for the Treatment of Anaphylaxis with and Without Shock
   • Strength 1:1000 (1 mg/ml), dosage for adults 0.3-0.5 ml , administered i.m. into the lateral surface of the thigh; see table T1.
   • Adrenaline injection can be repeated after 5-15 minutes; over one third of the patients need several doses.
   • To an adult patient in shock, adrenaline at strength 1:10 000 (0.1 mg/ml) can be given 0.5-1 ml slowly intravenously; for children the dose is 0.1-0.3 ml. May be repeated at intervals of a few minutes.
   • An intravenous adrenaline infusion is started if needed: 1 mg of adrenaline is diluted with 100 ml of 5% glucose solution. Infusion rate is 12-60 ml per hour.
   • Adrenaline may have reduced effect if the patient uses a beta blocker. In bradycardia and hypotension in patients using a beta blocker, the contractility of the heart can be enhanced by administering glucagon 1-5 mg i.v. in 5 minutes. The dose can be repeated.
2. Maintenance of vital functions
   • The patient should be in a half-sitting position (recumbent if hypotensive).
   • Make sure that the patient is breathing. Oxygen is administered through a mask if needed while monitoring the oxygen saturation.
   • An intravenous drip should be started with Ringer's solution or physiological NaCl solution. For a hypotensive adult, 500-1 000 ml should be given during the first hour, for a hypotensive child, 10-20 ml/kg over 15 to 30 minutes.
   • Blood pressure, heart rate and cardiac function should be monitored.
3. Intravenous glucocorticoids
   • For an adult methylprednisolone 80-250 mg, and for a child 2 mg/kg intravenously. Alternatively, hydrocortisone 250-1 000 mg for an adult and for a child 10 mg/kg intravenously. The total dose for a child must not exceed the dose for adults.
   • The effect starts slowly.
   • Predniso(lo)ne 30-50 mg orally, continued further for a few days (does not prevent recurrence).
4. Beta₂-sympathomimetics
   • Adrenaline and glucocorticoid are effective for asthma symptoms. Use also an inhaled drug like in asthma attacks, e.g. 2.5-5 mg of salbutamol via a nebulizer.
5. Antihistamines Antihistamines for Anaphylaxis in strong skin reactions
   • For an adult, cetirizine 10 mg or hydroxyzine 25-50 mg orally
   • For a child, cetirizine (age < 5 years 0.3 mg/kg, age > 5 years 10 mg)
   • For follow-up treatment for a few days
6. Follow-up
   • Follow-up for at least 6-8 hours is indicated even after a vanished or alleviated reaction. If needed, the follow-up may take place in a hospital. The reaction may recur (usually within 8 hours; in up to one fifth of the patients within 3 days).
   • When the patient is discharged, consider giving an auto-injector to take home especially if travel distances are long.

Prevention

• Patients should carry a preloaded adrenaline syringe for self-treatment of anaphylaxis. This is a disposable intramuscular adrenaline injection, and the patient and family members should be taught how to use it.
• The patient is advised to wear/carry a medical alert bracelet or card, especially if there have been repeated anaphylactic reactions.
• Instructions for the patient in an imminent reaction: immediate intramuscular adrenaline injection into the thigh, predniso(lo)ne 20 mg and antihistamine orally
• In wasp and bee allergy, specific desensitization therapy is given at the discretion of an allergologist.
• Foods that might cause allergy should not be tried out by the patient at home.