“Acute anaphylaxis”and

“anaphylactic reactions”

“Acute anaphylaxis”and

“anaphylactic reactions”

By: Dr.Dani MamoBy: Dr.Dani MamoBy: Dr.Dani Mamo

Definition

• Anaphylaxis is an acute, potentially fatal, multiorgan system reaction caused by the release of chemical mediators from mast cells and basophils.

• Anaphylactic reactions often begin with a feeling of uneasiness, followed by tingling sensations and dizziness.

• Then rapidly develop severe symptoms, including generalized itching and hives, swelling, wheezing and difficulty breathing, fainting, and/or other allergy symptoms.

Common causes

1) bee stings

2) wasp stings

3) other bites (e.g. imported red fire ants, jack jumper ants)

4) parenteral antibiotics, especially penicillin

5) food reactions (e.g. peanuts, fish).

Acute anaphylaxis with respiratory difficulty caused by a European wasp sting

• Other causes:

1) allergic extracts

2) blood products

3) antivenom

4) radiological contact materials

5) anaesthetic agents

• Note : The onset of anaphylaxis from exposure is usually rapid—typically 10–20 minutes. The diagnosis is basically a clinical one.

Signs and Symptoms(Eyes)

Signs and Symptoms (Skin)

Signs and Symptoms (nose & mouth)

Signs and Symptoms(Lungs & throat)

Signs and Symptoms(Heart and circulation)

Signs and Symptoms(Digestive system)

Signs and Symptoms(Nervous system)

Diagnosis

• The diagnosis of anaphylaxis is based upon symptoms that occur suddenly after being exposed to a potential trigger.

• An increased amount of tryptase protein can be measured in a blood sample collected during the first three hours after anaphylaxis symptoms have begun.

• tryptase levels are seldom elevated in food-induced anaphylaxis

Differential diagnosis

• severe asthma attack

• heart attack

• panic attack

• food poisoning

First-line treatment (adults)

• Oxygen 8 L/min (by face mask)

• Adrenaline 0.3–0.5 mg (1:1000) IM best given in mid antero-lateral thigh (mg = mL of 1:1000 adrenaline)

• Remove cause (e.g. bee sting) if possible.

• Set up IV access.

• If no rapid improvement:

repeat IM adrenaline every 3–5 minutes

set up adrenaline infusion: 1 mg adrenaline to 1000 mL N saline (i.e. 1 mL = 1 mcg adrenaline) bolus of 50 mcg ( = 50 mL) can be given as required (best with ECG monitor)

• Set up additional IV line (preferably two ‘wide bore’ lines) and infuse crystalloid solution (e.g. N saline 1–2 L) with bolus (20 mL/kg) over 1–2 min

• Salbutamol aerosol inhalation (or nebulisation if severe), especially if wheeze/stridor

• If very severe add glucagon 1 mg IM or IV

• Admit to hospital (observe at least 4 hours)

• Discharge on diphenhydramine 25 mg qid or promethazine 25 mg tds + prednisolone 50 mg/ day for 3 days.

• Provide an adrenaline autoinjector

Angioedema and acute urticaria

• Acute urticaria and angioedema are essentially anaphylaxis limited to the skin, subcutaneous tissues and other specific organs.

• They can occur together.

Treatment

• Uncomplicated cutaneous swelling—Antihistamines e.g. diphenhydramine or promethazine 50 mg (o) or 25 mg IM if more severe or prednisolone 25–50 mg (o) as a single dose

• Upper respiratory involvement adrenaline 0.3 mg SC or IM or 5 mg nebulised

Prevention of anaphylaxis

• Avoid the responsible allergen (e.g. food, drug, latex, etc.).

• Keep an adrenaline kit (e.g. Epipen) and Benadryl on hand at all times.

• Medic Alert bracelets should be worn.

• Venom immunotherapy is highly effective in protecting insect-allergic individuals.

Use of epinephrine inFood Allergy

• Epinephrine should be used immediately after accidental ingestion of foods that have caused anaphylactic reactions in the past.

• An individual who is allergic to peanut, nuts, shellfish, and fish should immediately take epinephrine if they consume one of these foods.

• A mild allergic reaction to other foods (e.g. minor hives,vomiting) may be treated with an antihistamine

Exercise induced anaphylaxis

• Exercise induces warmth, pruritus, urticaria.

• Hypotension and upper airway obstruction may follow.

• Some types: associated with food allergies (e.g. celery, nuts, shellfish, wheat)

• In other patients, anaphylaxis may occur after eating any meal (mechanism has not been identified)

Cold induced anaphylaxis

• Cold exposure leads to urticaria.

• Drastic lowering of the whole body temperature (e.g. swimming in a cold lake): hypotensive event in addition to urticaria

• mechanism: unknown

What to do ?? First Aid

• Place patient in Trendelenburg position.

• Establish and maintain airway.

• Give oxygen via nasal cannula as needed.

• Place a tourniquet above the reaction site.

• Epinephrine at the site of antigen injection.

• Start IV to rise BP.

References

• Davidson’s , principle & practice of medicine

• John Murtagh’s General Practice

• The_Merck_Manual_of_Diagnosis

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