Anaphylaxis Flashcards
(25 cards)
What systems can anaphylaxis involve?
- Skin and mucosa (90%): erythema, stridor, angioedema, obstruction, urticaria
- Respiratory (70%): dyspnoea, stridor, SOB, wheeze, hypoxaemia, resp arrest
- Reduced BP or associated symptoms (45%): tachycardia, hypotension, confusion, chest pain, reduced urine output
- Persistent GI symptoms (45%): vomiting and abdominal cramps
What key investigations would you order?
- ECG: before administrating adrenaline
- Vitals & haemodynamic stability
- Plasma histamine (peaks within 5-15 minutes, and declines to baseline 60 minutes after the event)
- Serum tryptase released by mast cells (peaks within 1-3 hours post exposure, stays elevated for 6+ hours)
- CXR
- IgE testing
- Skin test: intradermal, scratch or patch test
- Challenge test (exposure to the offending allergen; contraindicated if previous hx of anaphylaxis)
ABG: metabolic and respiratory acidosis.
Why does this occur in anaphylaxis?
- Respiratory acidosis: due to pharyngeal/laryngeal oedema and airway obstruction, with inability to blow off CO2, and by action of carbonic anhydrase it causes acidosis.
- Decreased bicarbonate/metabolic acidosis: lack of O2 supplying the peripheral tissues and organs leads to anaerobic metabolism resulting in lactic acidosis.
What are some common signs and symptoms of anaphylaxis?
Tachycardia and tachypnoea Stridor Pale, drowsiness Swollen face, eyes and tongue Urticaria Itchiness Bilateral wheezing and rhonchi
Describe underlying generic mechanisms of anaphylaxis that cause these signs and symptoms.
- Vasodilation: hyperaemia
- Distributive shock
- Airway obstruction via angioedema –> hypoxaemia
- Histamine mediated itchiness
- Angioedema from vasodilation and vascular leakage
Describe the hypersensitivity type 1 and cells involved.
Type 1 is IgE antibody-mediated hypersensitivity reaction. It can be mediated by bee stings, medications such as penicillin.
It has a quick onset, and lead to life-threatening anaphylaxis. It involves WCC such as basophils, eosinophils and mast cells. Body creates memory B cells and on subsequent exposure to the antigen, antibodies can attack.
Describe the hypersensitivity type 2 and cells involved.
Type 2 is cytotoxic reaction. It involves haemolytic anaemia, transfusion reactions, Goodpasture syndrome, hyperacute graft rejection.
It is mediated by IgG and IgM cytotoxic reactions. These occur as a result of reactions between antibodies and antigens on cell membrane surfaces. Immune response activates complement cascade, releasing biochemicals killing antigen-bearing cells.
Describe the hypersensitivity reaction type 3 and cells involved.
Type 3 is immune complex reaction. It involves hypersensitivity pneumonitis, SLE.
It is IgG and IgM mediated response. Unattached antigens enter blood circulation and activate immune response, with immune complex formation by platelets, neutrophils and immune-related substances. These clumps escape blood and deposit in organs and tissues causing problems.
Describe the hypersensitivity reaction type 4 and cells involved.
Type 4 is delayed reaction and cell-mediated response. It involves chronic graft rejection, latex and poison ivy.
It is T-cell mediated response, which takes weeks to manifest. Granuloma is a type 4 reaction, often as result of bacteria or fungi that the body is unable to eliminate.
Now for some pop quiz for hypersensitivity reactions!
ARE YOU SCAREEEED!!
Which type of hypersensitive reaction is:
Antihistamine used for?
Type 1 (IgE mediated)
Which type of hypersensitive reaction is:
Corticosteroid injection used for?
Type 2, 3 and 4
Which type of hypersensitive reaction is:
DMARD used for?
Type 3
Which type of hypersensitive reaction is:
Epinephrine injection used for?
Type 1
Which type of hypersensitive reaction is:
Immunosuppressive agent used for?
Type 3 and 4
Which type of hypersensitive reaction is:
Leukotriene receptor antagonists used for?
Type 1
Which type of hypersensitive reaction is:
Mast cell stabiliser used for?
Type 1
Which type of hypersensitive reaction is:
Monoclonal antibodies used for?
Type 1, 3 and 4
Which type of hypersensitive reaction is:
NSAIDs used for?
Type 3
What is the initial management of anaphylaxis? (non-pharm)
DRABCDEF Danger: antigen exposure? R: response S: send for assistance and code blue A: intubate if needed, protect from head injury or airway trauma B: high flow oxygen ~10L/min C: raise legs above heart, large bore cannulas D: neurological evaluation E: exposure F: adequate IV fluids
What are pharmacological interventions for anaphylactic shock?
IM adrenaline straight away
- Mid lateral thigh
- 1:1000 dilution ampule
- Repeat doses every 5 minutes as needed
Adrenaline infusion: if inadequate response and deterioration clinically
- 1 mL of adrenaline in 1000 mL saline
- Monitor and titrate well
Adjunct:
- Nebulised adrenaline
- Intubation
- Normal saline
- Glucagon bolus 1-2mg
- Vasoconstrictors and vasopressin after ICU consult
What do you give for wheezing and stridor?
- Bronchodilators salbutamol 8-12 puffs with spacer
2. ICS hydrocortisone or oral prednisolone
Adrenaline
MOA?
Alpha 1 receptor: vasoconstriction, increased peripheral vascular resistance, increase BP and decreased mucosal oedema
Beta 1 receptor: increased cardiac ionotropy and chronotropy –> increased HR
Beta 2 receptor: bronchodilation, decreased inflammatory mediator released
Down-regulates mast cell mediated responses (e.g. histamine and tryptase release)
Adrenaline
Side effects?
“Fight or flight” response
