Allergy including latex Flashcards
What is the incidence of anaphylaxis in anaesthesia
1 in 10 000 - 1 in 20 000
What % of anaphylactic reations are fatal
10%
Rank the agents (including latex) used in anaesthetics according to how frequently they cause anaphylaxis reactions during anaesthesia
1
Muscle relaxant - 58.2%
2
Latex - 16.7%
3
Antibiotics - 15.1%
4
Colloids - 4%
5
Hypnotics - 3.4 %
6
Opioids - 1.3%
7
Others - 1.3%
What is the overall incidence of anaphylaxis to muscle relaxants
1 in 6500
Most common because they are ‘functionally divalent’ meaning they can crosslink cell surface IgE –> H release from MAst cells without having to bind to haptens or large carrier molecules
How is it possible that anaphylaxis to NMB agents can occur on 1st exposure
Many over-the-counter drugs, cosmetics and food products contain tertiary or quaternary ammonium ions that can sensitize patients to muscle relaxants resulting in anaphylaxis in these patients on first exposure
If a patient has anaphylaxis to a benzylquinolinium, what percentage of these patients will also have anaphylaxis to an aminosteroid?
75% of patients display cross-reactivity between these two muscle relaxant groups
Are atracurium and mivacurium commonly associated with allergic anaphylaxis
No. They are associated with non-allergic anaphylaxis in which the release of mediators (especially histamine) from mast cells can mimic the presentation of the presentation produced by allergic anaphylaxis
Which antibiotics most commonly cause anaphylaxis
- Penicillin
- Cephalosporin
Together these cause 70% of anaphylaxis
Is it safe to administer propofol to egg allergic patients
Propofol is currently formulated in intralipid containing soybean oil, egg lecithin and glycerol. Current evidence indicates that it is safe to administer propofol to egg-allergic patients. The egg lecithin component of propofol is a highly purified egg yolk component and skin tests with propofol and its intralipid solvent were negative in patients with known egg allergy.
What is the incidence of anaphylaxis for thiopental and for propofol
Thiopental - 1 in 30 000
Propofol 1 in 60 000
Are there reports of anaphylactic reactions to volatile agents?
None
However: Very rare incidents of immune mediated hepatitis with Halothane, enflurane, isoflurane and desflurane
Describe immune disturbance related to the opioids
Morphine: non-immunological histamine release
Fentanyl - does not cause non-immunological histamine release
Which clinical conditions are often confused with true anaphylactic reactions to local anaesthetics?
A. Vaso-vagal reactions
B. Effects of adrenaline
C. ‘Panic attacks’
D. Systemic toxic effects of local anaesthetics
E. Reaction related to the additives in local
What type of local anaesthetic is more likely to cause anaphylaxis and why?
Ester LA are hydrolysed to PABA (para-aminobenzoic acid) which is a known allergen
True anaphylactic reactions are either from PABA or from a preservative: methylparaben
A drug allergy to which group of drugs requires avoidance of ester LAs and why
Patients with a sulphonamide allergy should not be prescribed ester LAs as the PABA molecule is structurally very similar to the sulphonamide molecule
What is the name of the tree from which natural rubber latex is derived?
Hevea Brasiliensis - milky white fluid
When does anaphylaxis to Natural Rubber Latex occur and how is the patient exposed?
Mucous membranes/surgical wounds/parenteral injection exposure
Usually occurs 1 hour after exposure
Describe the different types of latex reactions
- Type 1 hypersensitivity reaction
- Specific IgE to NRL proteins (most severe but least frequent) - Delayed type IV hypersensitivity reaction (contact dermatitis)
- Occurs 24 - 48 hours after repeated skin or mucosal contact (t-cell mediated and non-lifethreatening) - Non-immune mediated itching, irritation and blistering at the site of contact due to powder in the gloves, disinfectants and sweating
What can cause anaphylaxis during breast surgery? AN in what % of patients experience allergic reactions to this aspect of breast surgery?
Isosulfan blue dye used for lymphatic mapping and sentinal LN biopsy.
2% of patients exposed to blue dye have an allergic reaction
Apart from some colloids, where else is gelatin found and why is it relevant to anaesthesia
Found in colloids, sweets and vaccines
Can cause allergy
In which patients should all beta lactam antibiotics be avoided?
Severe allergic reaction to a beta lactam antibiotic
In which patients can 3rd generation cephalosporins be used as a substitute
Itchy rash must be further investigated for possible penicillin allergy. Penicillins and other beta lactam antibiotics must be avoided although 3rd generation cephalosporin drugs may be used where indicated. (No mucosal involvement and no non-itchy rash)
Which antibiotics contain a beta lactam ring
PENICILLINS
CEPHALOSPORINS
CARBAPENEMS
Benzylpenicillin, phenoxymethylpenicillin Flucloxacillin Amoxicillin Ampicillin Co-amoxiclav Pip-Taz Cephalosporins Carbapenems (including aztreonam)
Can the risk of perioperative anaphylaxis be mitigated through screening tests?
There is no test that can predict anaphylaxis
There is a very low positive predictive value for IgE specific assays and skin tests.
What are the goals of allergy centre referral
Determine the cause
Detect other drugs which may produce similar event
Determine drugs safe to use in future anaesthetics
Which patients are at increased risk of anaphylaxis during surgery.
what actions should be taken if there is increased risk
- Females
- History of atopy
- Previous anaphylaxis
- Unexplained reaction to previous anaesthetic: (hypotension/bronchospasm/urticarial rash/angioedema)
- Patients who say they are allergic to muscle relaxants or local anaesthetics
- Latex allergy
Elective –> refer patient to allergy centre
Emergency –>
- Consider RA,
- If GA required: no NMB and no Latex,
- Avoid drugs that cause H release (morphine/atracurium/gelatins)
- Pretreatment with Hydrocortisone H antagonists
- Prepare to treat anaphylaxis
Is atopy a risk factor for the development of antibodies to anaesthetic agents
No evidence. However, a history of atopy does increase risk of latex allergy. Furthermore, these patients are likely to be at higher risk for histamine release in agents that bring about such effects: when atracurium, morphine, propofol, gelatin are injected rapidly.
Give some examples of household items that contain latex
Household gloves, balloons, contraceptives, hot water bottles, erasers, rubber bands/balls, elastic waistbands/underwear.
If NRL allergy suspected –> send for testing before elective surgery
What should be done if a NRL allerguc patient cannot be positioned first on the operating list
A risk assessment must be undertaken to ensure that the area has had sufficient time to remove NRL particles from the air depending on the number of air changes within the room.
Anaesthesia and recovery should both take place in the operating theatre.
In what percentage of patients with an allergy to a specific muscle relaxant will experience anaphylaxis to a different class of muscle relaxant?
75%
How do allergic reactions to chlorhexidine normally present
CVS and cutaneous
