Anaphylaxis is a serious rapid in onset allergic reaction that may result in death.

Anaphylaxis is not common although, for unknown reasons, its incidence is increasing. Anaphylaxis occurs in all age groups. It is observed that the major causes of anaphylaxis vary with age, for example, food is a common trigger in the paediatric age group and medications more so in older adults.

Common causes of anaphylaxis include medications (antibiotics, non-steroidal analgesics, anaesthetics), insect bites (bees, wasps, jack jumper ants), and food (nuts, eggs, shellfish, seeds, wheat, cow’s milk). Sometimes a cause isn’t found (idiopathic anaphylaxis). For others, a “summation anaphylaxis” occurs when two or more factors conspire to trigger anaphylaxis; such as exercise and food.

The immunology of anaphylaxis is not entirely understood. Anaphylaxis may occur without any prior history, including to agents that a person has had prior uneventful exposure to or no known exposure at all. Predicting who may get anaphylaxis is difficult, but increased risk is anticipated for those with prior history, atopic history, multiple medication allergies, nut and/or shellfish allergy and asthma (especially if poorly controlled).

Following parenteral exposure (e.g. intravenous medications), the onset may be very quick, within minutes, presenting a challenging situation to manage.

Oral exposure may trigger anaphylaxis but after a longer period of time, within one to two hours following exposure.

The clinical symptoms involve the cardiovascular and/or respiratory system often also with cutaneous manifestations, such as itch, hives or angioedema. Gastrointestinal symptoms may occur also such as abdominal pain, diarrhea and vomiting. A clinician must identify involvement of the respiratory or cardiovascular system to differentiate anaphylaxis from a benign allergic reaction.

Airway swelling, shortness of breath, cyanosis, wheezing, a hoarse voice or stridor indicate respiratory system involvement. Cardiovascular system involvement, essentially markers of hypotension, include pallor, syncope, incontinence, floppy child, and confusion.

Patients with asthma or cardiovascular disease are especially at risk for severe anaphylaxis.

The key to managing anaphylaxis is to rapidly initiate treatment, specifically focusing on the prompt administration of ADRENALINE. Hence:

• Cease the consumption or administration of all agents. Remove stinger of bee.
• Do not leave patient in standing position; doing so may increase the risk of cardiac arrest. Lay the patient down if there is evidence of hypotension. Place in a sitting position if the patient is dyspnoeic. If vomiting, place in a lateral position.
• Summon for help—call 000
• Obtain adrenaline 1:1000 vial
• Administer 0.01ml/kg of 1:1000 adrenaline (using a 1ml syringe) intramuscularly into the anterolateral thigh
  • hence, for example, for a 70kg adult you will give 0.7mls of 1:1000 adrenaline IM into the anterolateral thigh
• Repeat this dose every 3-5 minutes for ongoing hypotension or evidence of airway compromise.
• Give oxygen
• Adjunctive treatment, if possible, includes:
  • 20ml/kg normal saline (0.9% sodium chloride) intravenously
  • 5mg/kg hydrocortisone intravenously (maximum 200mg)
  • salbutamol 5mg by nebulizer for wheezing
  • nebulised adrenaline (5mls i.e. 5 vials of 1:1000 adrenaline) for upper airway obstruction

Adrenaline is also available in an autoinjector device. EpiPen® and Anapen® are two brands of adrenaline autoinjectors. Both brands come as two types, one for children (EpiPen Jr®, Anapen Jr®) between 1 and 5 years of age and one for children or adults over 5 years of age (EpiPen®, Anapen®). For both brands, the junior and adult autoinjector respectively administer 0.15mg and 0.3mg of adrenaline also into the anterolateral thigh. The autoinjectors should not be used in infants less than one year of age.

Two adrenaline autoinjectors are recommended to be prescribed to patients who have had anaphylaxis or if there’s clinical concern of risk such as food allergy in patients with moderate to severe, persistent asthma. The autoinjectors can also be purchased without prescription. Some familiarity and training is required for efficient and safe use.

Cardiopulmonary resuscitation should commence if the patient does not respond to treatment and deteriorates to the point of being unresponsive and not breathing.

All patients who have had anaphylaxis require a period of observation in hospital as symptoms may recur (“rebound anaphylaxis”).

Referral to an allergy specialist and prescription of an adrenaline autoinjector including training is indicated. Trainer devices can be obtained to aid in demonstrating correct use of the autoinjector. An anaphylaxis action plan and MedicAlert bracelet assists patient management.

To remember the above, preparation is the key, which may include hanging a wall chart or other aide memoire, putting together a kit with 1ml vials of 1:1000 adrenaline, and 1ml syringes and needles.

The Australasian Society of Clinical Immunology and Allergy has excellent resources for health professionals and patients.

AUTHOR | Dr Ron Sultana – Director Epworth Emergency
Dr Sultana is an emergency physician and director of Epworth Richmond’s emergency department. Ron has worked in the private sector for over 14 years. A key focus of his is to progress emergency medicine within the private healthcare sector by striving to develop a team and environment that provides consistent excellent patient care and to use knowledge of current research trends to evolve practice. Ron also has a keen interest in clinical decision-making, medicolegal issues, research, biostatistics and health informatics.
Professional associations: Australian College of Emergency Medicine (ACEM)