Anaphylaxis 5/31/2015

Transcription

1 1 Definition of anaphylaxis Anaphylaxis Jon Kyle Andersen Anaphylaxis is a severe, life-threatening, generalised or systemic hypersensitivity reaction. It is characterised by rapidly developing, life-threatening problems involving the airway (pharyngeal or laryngeal oedema) and/or breathing (bronchospasm with tachypnoea) and/or circulation (hypotension and/or tachycardia). In most cases, there are associated skin and mucosal changes NICE guidelines [CG13] reviewed August Definition of anaphylaxis What happens during anaphylaxis Such signs and symptoms may be classified as a severe allergic reaction rather than anaphylaxis. However, the person should be classed as experiencing a suspected anaphylactic reaction and be treated as such. A confirmed diagnosis of anaphylaxis may happen too late for optimal treatment to work, as adrenaline is less effective for established anaphylaxis Any life-threatening sign or symptom needs early adrenaline and oxygen to halt the progress of the disease a difficult decision There are multiple processes and multiple interacting pathways (molecular, cellular/tissue, organs, whole body), and different pathways dominate in different reactions Different organs are affected to different degrees: in different people in different reactions in the same person 3 What happens during anaphylaxis What happens during anaphylaxis The reaction usually peaks within one hour, and usually passes within hours Some reactions may not peak until six hours, and may not pass until two days 5 Mast cell activation Histamine release Vasodilation Bronchoconstriction Capillary leakage Upper and lower airway obstruction Shock Miscarriage Vomiting Panic Sense of impending doom 6 1

2 3 Causes 3 Causes Foods such as nuts, dairy products, eggs, fish Exercise (EIA or FDEIA) Bee or wasp stings Natural latex (rubber) Food reactions cause respiratory arrest typically after minutes Insect stings cause collapse from shock after minutes Deaths from IV medication occur most commonly within five minutes Any drug or injection 7 8 Recognition and Treatment Anaphylaxis is highly likely when the following three criteria are met: Airway Sudden onset and rapid progression of symptoms Life-threatening problems with the Airway and/or Breathing and/or Circulation Skin and/or mucosal changes Exposure Breathing Exposure to a known allergen/trigger supports the diagnosis Disability Circulation 9 10 Life-threatening Airway Feeling that the throat is closing up Swelling of the face, throat or tongue Hoarse voice Stridor Difficulty swallowing Life-threatening Breathing Wheezy breathlessness Shortness of breath Increased respiratory rate Respiratory Arrest! 11 1

3 Life-threatening Circulation Disability Signs of shock Feeling faint/dizzy Increased heart rate Collapse Cardiac Arrest Reduced level of consciousness Tiredness Weakness Confusion Sense of impending doom 13 1 Endorsed at: Exposure Skin changes are often the first feature and are present in > 80% of cases Erythema / Urticaria / Angioedema / Cyanosis Biphasic anaphylaxis two examples 1. Bronchospasm and mucus plugging typically peak between minutes. The patient improves with adrenaline, but then suffers respiratory arrest. Blood pressure is needed to produce urticaria and angioedema, so these may disappear in shock. Adrenaline raises BP and may lead to the (re) appearance of urticaria and angioedema. The patient appears safe, but the airway now obstructs

4 Adrenaline (IM) 500 mcg age greater than mcg age 6 to mcg age less than 6 Emerade Epipen Jext Shelf life 30/1 18/1 18/1 Dosages Exposed needle length Time against thigh 16 mm (150 mcg) 5 mm (300 & 500 mcg) 15.0 mm mm 5 seconds 10 seconds 10 seconds Keep it simple Activation method Place & push Swing & jab Press & jab, or Swing & jab 0 19 Needle length Oops! 1 MHRA Adrenaline Auto-injectors: A Review of Clinical and Quality Considerations 0 June 01 3 (p) The best place for the injection is considered to be the side of the thigh in the middle between the hip and the knee, as recommended in the Resuscitation Council Guidelines (p5) Two studies measured the skin to muscle distance in adults and children and showed that the skin to muscle depth is greater than the length of the needle (15mm) in many people, particularly women due to a different distribution of fat from men

5 (p9) One injection from an auto-injector should be given immediately when symptoms are recognized and a second injection can be given 5 15 minutes later if symptoms are not improving. Therefore patients known to be at risk of anaphylaxis should have access to at least two AAIs (p9) The Resuscitation Council guidelines advise that patients should always be observed after treatment for anaphylaxis, for at least 6 hours and up to hours in adults, and for 1 to hours in children, as symptoms can recur up to hours after the initial reaction (this is called a biphasic reaction). The incidence of biphasic reactions is reported as 1-0% and unfortunately it is not possible to predict which patients will experience a biphasic reaction 5 6 (p10) The amount of adrenaline in the blood is halved in about.5 minutes. However, by subcutaneous or intramuscular routes, local constriction of the blood supply slows the absorption, so that the effects build up and last much longer than the half-life of.5 minutes would predict Oral presentation by Dr Rececca Knibb of Aston University, at the Food Allergy and Anaphylaxis Meeting (FAAM) in Dublin on 10 October 01 Participants (n=90 adults) were randomly assigned to Jext, EpiPen or Emerade. A simulated scenario involved a live patient acting unconscious after eating something they were allergic to; a loud ambulance siren played throughout. Participants were asked to give the person an injection of adrenaline in the leg, using a trainer pen with no instructions available. They were then asked to give a second shot with a pen of the same design with instructions. The simulation was scored by the researcher and video recorded; participants were interviewed about their experience. 7 8 Oral presentation by Dr Rececca Knibb of Aston University, at the Food Allergy and Anaphylaxis Meeting (FAAM) in Dublin on 10 October 01 Without label instructions, 77% of participants successfully administered Emerade, compared to 7% with Jext and 0% with EpiPen (p<0.001). With label instructions, 100% of participants successfully administered Emerade, compared to 57% with Jext and 3% with Epipen (p<0.001). Participants also took significantly less time to administer adrenaline with Emerade (mean=1.73 seconds), compared to Jext (9.1) or EpiPen (33.7) 9 Oral presentation by Dr Rececca Knibb of Aston University, at the Food Allergy and Anaphylaxis Meeting (FAAM) in Dublin on 10 October 01 Instructions on Jext and EpiPen were confusing and skim read by participants, thus they missed important information. Emerade was reported to be easy to use both with and without instructions and pictures were easy to follow. Emerade is an intuitive easy to use AAI compared to Jext or EpiPen. In this simulated emergency situation participants found it difficult to read and act on written instructions. This is likely to be more pronounced in a real emergency where an AAI might be used by someone with little or no training. Instructions on AAIs need to be simplified with less complicated designs. 30 5

6 current/3-respiratory-system/3- antihistamines-hyposensitisation-and-allergicemergencies/33-allergicemergencies/anaphylaxis/adrenalineepinephr ine/intramuscular-injection-for-selfadministration/emerade Dose by intramuscular injection, ADULT and CHILD over 1 years at risk of severe anaphylaxis, 500 micrograms repeated after 5 15 minutes as necessary Thank you for listening and taking part