ANAPHYLAXIS

• Anaphylaxis is a severe systemic allergic reaction
• Consider if rapid onset of respiratory difficulty and/or hypotension
  • especially if rash and/or angioedema present

Symptoms and signs

Airway

• Upper airways obstruction due to angioedema:
  • swelling of tongue/throat
  • stridor
  • feeling of throat closing
  • hoarse voice

Breathing

• Lower airways obstruction:
  • wheeze
  • increased respiratory rate
  • cyanosis

Circulation

• Signs of shock:
  • impaired capillary refill (capillary refill time >2 sec)
  • tachycardia
  • hypotension

Disability

• Confusion
• Agitation
• Loss of consciousness

Exposure

• Skin and mucosal changes (may not be present in all patients):
  • redness or blotchy rash
  • urticaria
  • itching
  • angioedema
  • rhinitis and conjunctivitis

Other systems affected

• Gastrointestinal:
  • abdominal pain
  • vomiting
  • diarrhoea

Investigations

• Mast cell tryptase – sample serum at following times
  • as soon as possible after emergency treatment has started
  • at 1–2 hr from onset of symptoms. No later than 4 hr
• Patient may present late. Take as many serum samples as time since presentation allows
  • indicate time and date clearly to allow interpretation of results
• Inform patient that a final sample will be necessary to measure baseline levels in follow-up

Differential diagnosis

• Syncope (rapid recovery) with bradycardia in vagal reaction
• Septic shock with a petechial or purpuric rash
• Acute cardiac event
• Panic attack with hyperventilation (unlikely to be hypotensive)
• Acute severe asthma
• Other causes of central airways obstruction
  • idiopathic non-allergic urticaria and angioedema

• All doses are for adults

Diagnosis

Look for

• Acute onset of illness
• Life-threatening Airway and/or Breathing, and/or Circulation problems
  • Airway: Swelling, hoarseness, stridor
  • Breathing: Rapid breathing, wheeze, fatigue, cyanosis, SpO2 <92%, confusion
  • Circulation: Blotchy and red, clammy, low blood pressure, faintness, drowsy/coma
• Usually skin changes

Call for help

• Lay patient flat and elevate feet to restore/maintain BP. Do not stand patient up
  • if this causes respiratory distress, sit patient up

Adrenaline

• For hypotension or respiratory distress with stridor or wheezing, give adrenaline:
  • 500 microgram (0.5 mL of 1:1000 solution) IM into midpoint of anterolateral aspect of thigh
  • if an adult EpiPen^® is more readily available give this (delivers 300 microgram dose of adrenaline)
• If hypotension and respiratory distress do not respond within 5 min:
  • give further dose of adrenaline 500 microgram IM (0.5 mL of 1:1000 solution)
• Can be repeated at 5 min intervals according to BP, heart rate and respiratory function
  • monitor vital signs continuously
• IV adrenaline is hazardous
  • use only with extreme care, and under critical care supervision, for those in profound shock that is immediately life-threatening

When skills and equipment available

Establish airway

• If concerned about patient’s respiratory effort/airway obstruction, contact anaesthetist

High-flow oxygen

• Oxygen at high flow rate (10–15 L/min) – see Oxygen therapy in acutely hypoxaemic patient guideline

IV fluid challenge

• Establish IV access
• If systolic BP <100 mmHg, give fluid challenge of compound sodium lactate (Hartmann’s) 500 mL as quickly as possible. See Fluid resuscitation guideline
• Stop IV colloid if this might be cause of anaphylaxis

Chlorphenamine

• Chlorphenamine 10 mg by IM or slow IV injection

Bronchospasm

• If there is bronchospasm, give salbutamol 5 mg via oxygen driven nebuliser
  • for further treatment of bronchospasm, see Acute severe asthma in adults guideline
• If patient has been taking a non-cardioselective beta-blocker [e.g. propranolol, oxprenolol, sotalol, timolol (including eye drops)], severity of anaphylaxis may be increased and response to adrenaline antagonised
  • consider giving salbutamol by slow IV injection – see Salbutamol IV guideline

Severely ill patient

• When patient severely ill and there is real doubt about adequacy of circulation and absorption after IM injection, call critical care staff to attend urgently
  • transfer to critical care as soon as possible

Further treatment under critical care supervision

• Consider giving adrenaline 50 microgram (0.5 mL of the dilute 1:10,000 adrenaline injection) by slow IV injection, no faster than 1 mL/min while monitoring cardiac rhythm.
  • Repeat according to response
• If multiple doses required, give adrenaline as slow IV infusion, stopping when response obtained

• Monitor (including ECG) continuously all patients experiencing severe anaphylaxis until condition stabilised
  • then every 15 min for 1 hr until completely stable
• Continue to record hourly:
  • heart rate
  • blood pressure
  • respiratory rate
  • if possible, peak expiratory flow (PEF)
  • SpO₂ 

• Record time of onset of symptoms and identify possible allergens
  • e.g. drugs, foods (within previous hour), insect stings, latex
• Until all allergic symptoms have subsided completely, consider prednisolone 30 mg oral daily
• Chlorphenamine 4 mg oral 6-hrly (for at least 24–72 hr to prevent relapse) or until all allergic symptoms have subsided completely
• Warn patient of possible early recurrence and keep under observation for at least 6 hr.
• Consider prolonged observation for patients who:
  • developed symptoms during night, who may not be able to respond to any deterioration in clinical condition
  • live in areas where access to emergency care difficult

Likelihood of early recurrence

• Increased in patients:
  • with slow-onset severe reaction resulting from idiopathic anaphylaxis
  • with severe asthma
  • at risk of continued absorption of allergen
  • with previous history of biphasic reactions

• Senior clinician reviews patient before discharge
• Patient given clear instructions to return to hospital if symptoms return
• Advise avoidance of allergen if appropriate
• Management plan to include use of antihistamines for any allergic symptoms and EpiPen^® and 999 call for life-threatening symptoms of dyspnoea or faintness
• Prescribe 2 auto-injector devices containing adrenaline 300 microgram (EpiPen^{® )}
  • instruct patient on when and how to use
• Give patient contact details for SOS Talisman to obtain alert jewellery containing vital information on their condition in case of emergency
• Give patient contact details of Anaphylaxis Campaign,
• Send outpatient referral