2.1.4 Anaphylaxis Flashcards
What is anaphylaxis?
Severe life threatening hypersensitivity reaction
Rapid onset
Potentially life-threatening airway, breathing or circulatory problems
Usually associated with skin and mucosal changes
How rare is anaphylaxis mortality?
Extremely rare
More likely to die from fire or murder
How can anaphylaxis occur?
Immunologic IgE or non-IgE
Non-immunologic
How is the body affected by anaphylaxis?
Multiple organ dysfunction
use ABC approach
What makes anaphylaxis difficult to recognise?
Different reaction patterns
Skin manifestations are subtle and not present in 20%
In infants mimics other conditions
What is the clinical criteria for diagnosing anaphylaxis?
VERY LONG CARD :/
Anaphylaxis highly likely when one of the 3 criteria are met
Acute onset of illness - minutes to hours, with involvement of skin, mucosal tissue or both AND 1:
- Respiratory compromise
- Reduced BP or associated symptoms of end organ dysfunction eg syncope
Two or more of the following that occur rapidly after exopsure to likely allergen:
- Involvement of skin/mucosa
- Respiratory compromise
- Reduced BP or associated symptoms
- Persistent GI symptoms
Reduced BP after exposure to known allergen for that patient
- Infants low systolic for age or >30% decrease,
- Adults <90mmHg or >30% decrease from persons baseline
What are the mast cell mediators involved in anaphylaxis?
Histamine
Tryptase
Platelet activating factor
How are reactions different in children vs adults?
Upper respiratory much more common in kids vs adults
Lower respiratory more common in kids vs adults
Cutaneous, GI and CVS slightly more common in kids vs adults
Neurological slightly more common in adults than kids
What is the most likely cause of anaphylaxis in kids?
Foods e.g. peanuts or milk
What are the likely causes of anaphylaxis in adults?
Drugs e.g. Abx, NSAIDS
Insect stings e.g. wasps
Food e.g. fish, nuts
What is the differential diagnosis of anaphylaxis?
Common entities
- Syncope
- Asthma
- Panic attack
Post-prandial events
- Pollen-food syndrome
- Scromboidosis
Shock
- Hypovolaemic or cardiogenic
- Distributive
- Septic
Non-organic disease
- Vocal cord dysfunction
- Factitious induced illness
Others
- Phaeochromocytoma
- Thyrotoxicosis
How is anaphylaxis managed acutely?
- Assessment A-E
- Treatment IM adrenaline, oxygen, IV fluids, supine
- Treatment if needed IM adrenaline, beta-agonists, antihistamines, steroids, volume
How is anaphylaxis managed long-term?
- Emergency preparedness
- Assess/treat co-morbidites
- Allergen avoidance
- Immuno-modulation
Compare the use of adrenaline and antihistamines in treating anaphylaxis?
Adrenaline is used for higher severity anaphylaxis, e.g. when CVS or multiple systems are involved
Antihistamines are used for more mild anaphylaxis, e.g. skin reaction only
Adrenaline is effective for all symptoms
How can you identify the allergen responsible for anaphylaxis?
History of event
Examination
Allergy tests
What are the factors of long term ananphylaxis management?
Age
- Infants
- Adolescents
- Elderly
Concomitant disease and medication
- Asthma and other respiratory diseases
- Cardiovascular disease
- Psychiatric illness
Cofactors
- Stress
- Infection
- Exercise
Allergens
What are the factors determining risk of developing anaphylaxis?
Allergen
- Molecular weight and stability (heat stable or labile)
Sensitisation
- Immunoglobulin classes, their proportion and affinity, strength of sensitisation
Route of allergen contact
- Affects absorption
Prescence of co-factors
- Modulate absorption, activation and release of mediators
How do we decide who needs an adrenaline auto-injector?
Given when a patient has a high risk of developing anaphylaxis to a common allergy
Give 4 examples of intrinsic co-factors which affect the risk of anaphylaxis
Atopic disease e.g. asthma, eczema
CV disease
Skin disease
Other allergies
What is an extrinsic co-factor affecting the risk of anaphylaxis?
Drugs
Give 4 examples of direct modulating co-factors affecting risk of anaphylaxis
Exercise
Alcohol consumption (increased consumption lowers threshold for anaphylaxis)
Infectious disease
NSAIDs
When should adrenaline autoinjectors be used?
Think 3 āDā
- Is it a definite reaction?
- Is it a dangerous reaction
- Do it if in doubt
What systems are involved for antihistamine use?
GI
Skin
What systems are involved for adrenaline use?
Respiratory
CVS
CNS
