Anaphylaxis

• It’s a severe, life-threatening, generalized, or systemic hypersensitivity reaction, characterized by rapidly developing and life-threatening airway, breathing, and/or circulation problems, usually associated with skin and mucosal changes.

• Causes

• Medication:
• Antibiotic (penicillin most common)
• NSAID
• Aspirin
• ACEI
• Anesthetic agent eg: muscle relaxant (Suxamethonium and rocuronium) and contrast media

• Others

• Food: eg: peanut , egg seafood (most common in children).
• Insect sting
• latex
• idiopathic
• C1 esterase etc.

• Management

• Key points

• Anaphylactic likely when following 3 criteria match:
• 1:acute onset of illness with a sudden progression. 
•  2:a life-threatening airway and/or breathing and/or circulation problem.
•  3: possible skin or mucosal changes (although these may be absent and are not required for diagnosis).
• there is no role of antihistamine however it may help alleviate cutaneous symptoms.
• The routine use of corticosteroids to treat anaphylaxis is not advised. If the patient is suffering from ongoing asthma/shock after initial resuscitation steroids may be considered.
• Use glucagon in patients who are taking beta blockers may be resistant to the therapeutic effects of adrenaline.
• Adrenaline : can give second dose if reaction persist after 5 minutes interval. After 2 doses, adrenaline infusion should be started. 
• Nice recommend 6 hours observation: those pt who has 2 doses of IM adrenaline or previous biphasic reaction.
• 12 hours observation : those ptwho has required more than two doses of adrenaline, has severe asthma or their reaction has involved severe respiratory compromise.
• The frequency of food sensitization in asthmatic children is higher than expected in a general population. it has been found that asthma is a risk factor for severe or fatal anaphylactic reactions to foods
• Investigation : resus council recommend 3 tryptase level. First as resuscitation started, 2nd 1-2 hours after symptoms started. 24 hours later.

• Anaphylactoid vs anaphylaxis:

• Anaphylactoid reaction: first time exposure to allergen , direct release of histamine and other mediators from mast cells and doesn’t cause degranulation. Non-immune (IgE) mediated reaction.
• Anaphylaxis reaction: On further exposure to that allergen, the responsible allergenic antigen binds to an antigen-specific IgE antibody, leading to mast cell degranulation Histamine and other mediators, including leukotrienes and cytokines are released from mast cells and basophils following exposure to this antigen.
• Summery: anaphylactoid first exposure and non-immune mediated
• Anaphylaxis: further exposure/ Pt has exposed to allergen previously (history) and immune mediated.

• NICE recommendation prior to discharge

• NICE recommends that prior to discharge, a healthcare professional with the appropriate skills and competencies should offer patients (or their parent/carer) the following:
• information about anaphylaxis, including the signs and symptoms of anaphylaxis
• information about the risk of a biphasic reaction (and clear instructions to return to hospital if symptoms return)
• information on what to do if anaphylaxis occurs
• prescription of adrenaline auto-injectors and demonstration of the correct use of the adrenaline injector and when to use it
• advice about how to avoid the suspected trigger
• information about the need for referral to a specialist allergy service and the referral process
• information about patient support groups.

• Patients should be provided with an emergency management or action plan.
• adrenaline auto-injector

• A prescription for two should be given rather than a single auto-injector
• Patients should be advised to have the auto-injector easily available at all times (including for example in school, on holidays or when away from home).
• Three types are commercially available (EpiPen®, Jext® and Emerade®).
• They come in 0.3ml and 0.15ml strengths (EpiPen® and Jext®) and 0.5ml, 0.3ml and 0.15ml strengths (Emerade®) with varying shelf-lives, prices and needle lengths