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Acute Anaphylaxis

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Anaphylaxis is a severe, life-threatening, generalised or systemic hypersensitivity reaction. Adrenaline 0.5 mg (0.5 ml) IM of 1:1000 is potentially life-saving and must therefore promptly be administered as the first-line treatment for the emergency management of anaphylaxis. It is given through clothes if needed IM into the lateral thigh

Acute Anaphylaxis
First steps Sudden onset: Airway and/or Breathing and/or Circulation problems + skin changes (e.g. wheals, urticaria) Call for HELP: Resuscitation team/MET call or ambulance Initial Management Summary: Resuscitation UK Remove trigger if possible (e.g. stop any infusion/transfusion, remove bee/wasp sting, stop eating) Position:Lie patient flat. Lift legs and keep them elevated. A sitting position may make breathing easier for some. If the patient is > 20 weeks pregnant, lie on left side Give IM Adrenaline (Epinephrine 1:1000) into lateral thigh Adult or Child Age>12 yo: IM 0.5mL/0.5 mg Child Age 6-12 yo 0.3mL/0.3 mg Child Age < 6 yo 0.15 mg/0.15 ml Child 6 months to 6 years: 150 micrograms IM (0.15 mL) Child <6 months: 100–150 micrograms IM (0.1–0.15 mL) High-flow O₂ (15 L/min) and preserve airway. Lie flat. If no response after 5 minutes Repeat IM Adrenaline (Epinephrine 1:1000) into lateral thigh Give IV fluids 500-1000 ml N-Saline. Children 20 ml/kg of N-Saline or other Crystalloid Salbutamol/Albuterol 5 mg neb if wheeze. Senior help if fails to respond Send Mast cell tryptase sample, CXR, ECG, ABG if needed These are not now included in current UK Guidelines Hydrocortisone 200 mg IM or slow IV Chlorphenamine 10 mg IM or slow IV If No improvement clinically despite 2 x IM Adrenaline 0.5 mg then continue with an Adrenaline Infusion and follow the refractory pathway below Refractory Anaphylaxis Give rapid IV fluid bolus e.g. 0.9% sodium chloride Start Adrenaline/Epinephrine infusion as a peripheral low-dose infusion Adrenaline 1 mg (1 mL of 1 mg/mL [1:1000]) in 100 mL of 0.9% sodium chloride. Prime and connect with an infusion pump via a dedicated line. DO NOT ‘piggy back’ on to another infusion line. Avoid same side as a BP cuff. In both adults and children, start at 0.5–1.0 mL/kg/hour, and titrate according to clinical response Continuous monitoring/observation. High BP suggests excessive adrenaline dose Airway Partial upper airway obstruction/stridor: Nebulised adrenaline (5mL of 1mg/mL) Total upper airway obstruction: Expert help needed, follow difficult airway algorithm Breathing: Oxygenation is more important than intubation If apnoeic (not breathing) Bag mask ventilation Consider tracheal intubation Severe/persistent bronchospasm Salbutamol/Ipratropium neb with O₂ Consider IV bolus and/or infusion of salbutamol or aminophylline Inhalational anaesthesia Circulation: Give further fluid boluses (glucose-free crystalloid (e.g. Hartmann’s Solution, Plasma-Lyte®) and titrate to response Child 10 mL/kg per bolus Adult 500–1000 mL per bolus. Large volumes may be required (3–5 L in adults) Place arterial cannula for continuous BP monitoring and central venous access If refractory to Adrenaline infusion consider adding a second vasopressor in addition to adrenaline infusion Noradrenaline, vasopressin or metaraminol In patients on beta-blockers, consider glucagon Consider extracorporeal life support Cardiac arrest – follow ALS ALGORITHM Start chest compressions early Use IV or IO adrenaline bolus (cardiac arrest protocol) Aggressive fluid resuscitation Consider prolonged resuscitation/extracorporeal CPR

Acute Anaphylaxis

First steps

Sudden onset: Airway and/or Breathing and/or Circulation problems + skin changes (e.g. wheals, urticaria)
Call for HELP: Resuscitation team/MET call or ambulance

Initial Management Summary: Resuscitation UK

Remove trigger if possible (e.g. stop any infusion/transfusion, remove bee/wasp sting, stop eating)
Position:Lie patient flat. Lift legs and keep them elevated. A sitting position may make breathing easier for some. If the patient is > 20 weeks pregnant, lie on left side
Give IM Adrenaline (Epinephrine 1:1000) into lateral thigh
- Adult or Child Age>12 yo: IM 0.5mL/0.5 mg
- Child Age 6-12 yo 0.3mL/0.3 mg
- Child Age < 6 yo 0.15 mg/0.15 ml
- Child 6 months to 6 years: 150 micrograms IM (0.15 mL)
- Child <6 months: 100–150 micrograms IM (0.1–0.15 mL)
High-flow O₂ (15 L/min) and preserve airway. Lie flat.
If no response after 5 minutes Repeat IM Adrenaline (Epinephrine 1:1000) into lateral thigh
Give IV fluids 500-1000 ml N-Saline. Children 20 ml/kg of N-Saline or other Crystalloid
Salbutamol/Albuterol 5 mg neb if wheeze. Senior help if fails to respond
Send Mast cell tryptase sample, CXR, ECG, ABG if needed
These are not now included in current UK Guidelines
- Hydrocortisone 200 mg IM or slow IV
- Chlorphenamine 10 mg IM or slow IV
If No improvement clinically despite 2 x IM Adrenaline 0.5 mg then continue with an Adrenaline Infusion and follow the refractory pathway below

Refractory Anaphylaxis

Give rapid IV fluid bolus e.g. 0.9% sodium chloride
Start Adrenaline/Epinephrine infusion as a peripheral low-dose infusion
- Adrenaline 1 mg (1 mL of 1 mg/mL [1:1000]) in 100 mL of 0.9% sodium chloride. Prime and connect with an infusion pump via a dedicated line. DO NOT ‘piggy back’ on to another infusion line. Avoid same side as a BP cuff.
- In both adults and children, start at 0.5–1.0 mL/kg/hour, and titrate according to clinical response
- Continuous monitoring/observation. High BP suggests excessive adrenaline dose
Airway
- Partial upper airway obstruction/stridor: Nebulised adrenaline (5mL of 1mg/mL)
- Total upper airway obstruction: Expert help needed, follow difficult airway algorithm
Breathing: Oxygenation is more important than intubation
- If apnoeic (not breathing)
  - Bag mask ventilation
  - Consider tracheal intubation
- Severe/persistent bronchospasm
  - Salbutamol/Ipratropium neb with O₂
  - Consider IV bolus and/or infusion of salbutamol or aminophylline
  - Inhalational anaesthesia
Circulation:
- Give further fluid boluses (glucose-free crystalloid (e.g. Hartmann’s Solution, Plasma-Lyte®) and titrate to response
  - Child 10 mL/kg per bolus
  - Adult 500–1000 mL per bolus. Large volumes may be required (3–5 L in adults)
- Place arterial cannula for continuous BP monitoring and central venous access
- If refractory to Adrenaline infusion consider adding a second vasopressor in addition to adrenaline infusion
  - Noradrenaline, vasopressin or metaraminol
  - In patients on beta-blockers, consider glucagon
- Consider extracorporeal life support
Cardiac arrest – follow ALS ALGORITHM
- Start chest compressions early
- Use IV or IO adrenaline bolus (cardiac arrest protocol)
- Aggressive fluid resuscitation
- Consider prolonged resuscitation/extracorporeal CPR

Treat if there are any Life-threatening ABC features: Hoarse voice, stridor, increased work of breathing, wheeze, fatigue, cyanosis, SpO₂ <94%, Low blood pressure, signs of shock, confusion, reduced consciousness. Rash alone is not listed but be observant for ongoing changes.

Swelling of lips, tongue, pharynx, and epiglottis may lead to complete upper airway occlusion. Lower airway involvement is similar to acute severe asthma — dyspnoea, wheeze, chest tightness, hypoxia, and hypercapnia

Introduction

Anaphylaxis is a potentially fatal reaction to an allergen.
Adrenaline given IM improves prognosis and can be life-saving.
Adrenaline IM should be given where there is clinical suspicion of anaphylaxis.
The key signs are hypotension or skin changes or wheeze or stridor.
Always summon senior help such as 999 immediately if no rapid recovery.
In hospital call for the medical emergency team.
Never give IV Adrenaline (Epinephrine) in anaphylaxis.
IV Adrenaline should only be used in cardiac arrest protocol.

Aetiology

With anaphylaxis there is Mast cell degranulation due to antigen cross linking IgE on cell surface.
This leads to the systemic release of histamine which binds to H1, H2, H3 and H4 receptors.
There is then a massive release of cytokines and chaemokines.
Requires prior exposure and formation of allergen specific IgE.
Increased post capillary venule permeability oedema.
Vascular smooth muscle relaxation - hypotension

Causes

Causative agents, Drugs e.g. Penicillin, Radiological contrast media.
Insect stings, Eggs, Fish, Peanuts, Latex.
Giving blood products e.g. IVIG to those with selective IgA deficiency

Clinical

Feeling faint, breathless, wheezing, stridor, clammy skin, confusion and anxiety
Collapsing or losing consciousness, Colic and diarrhoea and vomiting
Abdominal pain, flushing, Wheeze, Urticaria (not with C1 esterase deficiency)
Facial, lips swell, Laryngeal oedema can compromise airway - stridor

Differential

Septic shock: warm, vasodilated. Blood cultures, FBC, CRP, lactate if sepsis considered. IV fluids.
Scombroidosis (Histamine)
Systemic mastocytosis
Faint (vasovagal episode).
Panic attack.
Breath-holding episode in child.
Idiopathic (non-allergic) urticaria or angioedema.
Phaeochromocytoma
Hereditary angioedema.

Investigation

FBC, U&E, LFTs, Lactate, ABG may be needed
Mast cell tryptase (level reflects the degree of hypotension) should be sent within 1 hour and 24 hours (or at follow up). It may not be elevated in food allergy. Send 10 mL of clotted blood should be taken within 60 min of the reaction for confirmation of the diagnosis: e.g. by measurement of the mast cell tryptase. Serum should be separated and stored at -20°C.
Later at an Immunology clinic - Allergen skin testing, RAST - identifies specific IgE

Prevention

Mistakes in cross matching or patient identification and giving the wrong blood
Avoiding Penicillin or other drugs when allergic
Avoiding food allergies
Having access to an EpiPen

Management

Assess ABCDE. Lay patient supine and raise legs/end of the bed if anaphylaxis possible. Call MET team. Get senior help quickly if fails to respond.
Stop causative drug or infusion or blood product, remove bee sting.
If airway issues get the anaesthetic team. HR, BP, Telemetry, sats
Give O₂ High flow 15L/min target 94-98%. Non-rebreather mask. May have to give less if COPD
Give Adrenaline (Epinephrine in US) 0.5 ml of 1 in 1000 stat IM. May be repeated at 5-minute intervals depending on the response. Give IM into the anterolateral aspect of the middle third of the thigh using a needle long enough to ensure the Adrenaline (Epinephrine) is given into the muscle. This can be given through clothes. Do not give IV Adrenaline unless cardiac arrest.
IV 500-1000 mls stat 0.9% N-Saline and titrate to BP and clinical status. Some may need several litres. Watch for overload in an older patient

Deprecated Treatments now

Salbutamol (Albuterol in US) 5mg and nebulise with O₂ if patient wheezy
Hydrocortisone 200 mg stat and 8-hourly as needed IV/IM and may be used as they may reduce the risk of late-phase respiratory symptoms
Antihistamine Chlorphenamine 10 mg stat IV (UK) or Benadryl/Diphenhydramine 25-50 mg stat IV(USA) and Ranitidine may also be given. Systemic H1-(& H2)-antihistamines may relieve cutaneous symptoms of anaphylaxis
Monitor for 6-12 hours following full recovery to ensure no late reactions. Such biphasic responses can occur. Before discharge, the risk of future reactions should be assessed and an adrenaline auto-injector should be prescribed to those at risk of recurrence. Ensure if given Epipens also instructed how to use it. Arrange or advise referral to a specialist for allergy clinic or immunology opinion and identification of cause and antigen avoidance.

References

PLEASE NOTE LEGAL ADVICE: The contents are under continuing development and improvements and may contain errors of omission or fact. Feedback vital and always welcome at drokane at gmail.com. This is not to be used for the assessment, diagnosis or management of patients. It should not be regarded as medical advice. It is only for educational purposes. Please adhere to your local protocols. If you are unwell please seek healthcare advice from your doctor. This does not replace senior or specialist advice. If you do not accept this then please do not use the website. If you need medical advice, please consult a doctor or other appropriate medical professional. If you are a medical professional and you need advice then speak to your senior or colleagues.

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