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Fellowship revision > Anaphylaxis > Flashcards

Anaphylaxis Flashcards

1
Q

Steps in management of anaphylaxis?

A
  • Call for help & anaphylaxis box, communicate (stop procedure) & delegate (eg. dedicated leader, scribe, reader of cards, lines, drugs/infusions)
  • remove suspected triggers
  • if no detectable CO, check rhythm, start CPR & arrest protocol, elevate legs
  • If CO detected, stop procedure, reduce agent, consider early intubation (if airway oedema or resp compromise) & turn O2 to 100%
  • give Adr according to severity
  • ensure adequate IV access, consider art line for samples & monitoring
  • give @ least 20mL/kg IV fluid (2L on anaphylaxis cards, warm if possible) & elevate legs, larger vols & further IV access may be needed
  • if signs persist, start Adr infusion but also consider 4Hs & 4Ts for other possible missed diagnoses
  • consider additional agents if refractory
  • consider CVC if difficult peripheral IV access or ongoing infusions needed
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2
Q

When are tryptases taken? what’s the ongoing therapy once stable?

A

1, 4 & >24hrs; start adjunctive therapy once stable & refer to allergy clinic, letter must be sent w pt including reaction description + agents used

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3
Q

What’s mild (grade 1) anaphylaxis?

A

generalised mucocutaneous signs: erythema, urticaria +/- angioedema

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4
Q

What’s moderate (grade 2) anaphylaxis?

A

multi-organ manifestation which may include:
hypotension, tachycardia
evidence bronchospasm, cough, difficult ventilation
mucocutaneous signs

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5
Q

What’s life-threatening (grade 3) anaphylaxis?

A

Severe multi-organ manifestation requiring immediate & specific Rx:
severe hypotension
Brady/tachycardia, arrhythmias
severe bronchospasm +/- airway oedema
cutaneous signs may be absent & then present after correction of hypotension

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6
Q

What’s grade 4 anaphylaxis?

A

Cardiopulmonary arrest

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7
Q

What are the doses for adult Adr for grade 2 & 3 anaphylaxis? IV & IM? When is the IV infusion started?

A

grade 2= 20microg (0.2mL) of Adr 100microg/mL, 1-2 minutely
Grade 3= 100-200microg (1-2mL)
If pt has required >3 Adr boluses, commence infusion (can administer peripherally): 3mg in 50mL, commence @ 3mL/hr (3microg/min) & titrate to a max of 40mL/hr (40microg/min), (0.05-0.5microg/kg/min)
Start the IV infusion asap- 0.1microg/kg/min (0.3mL/kg/hr), titrated to a max 6mL/kg/hr (2microg/kg/hr)

IM (1mg/mL) route used if no haemodynamic monitoring, no IV access; 0.5mL (500microg) IM lateral thigh 5-minutely PRN in those aged >12yo

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8
Q

How is Adr prepared for paediatric anaphylaxis? (different from paediatric arrest, where still have 100microg/mL but instead give 10microg(0.1mL)/kg)
What are the doses for paediatric Adr for grade 2 & 3 anaphylaxis? IV & IM?

A

1mg Adr diluted to 50mL in D5W which avoids oxidation in alkaline environment (20microg/mL)
grade 2= 2microg/kg (0.1mL/kg)
grade 3= 4-10microg/kg (0.2-0.5mL/kg)

IM, give 150microg (0.15mL) if <6yo & 300microg (0.3mL) if 6-12yo

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9
Q

What are the considerations & additional medications for refractory anaphylaxis, after commenced Adr infusion?
How about for B-blocker reversal?

A

Consider occult triggers (chlorhex-impregnated CVCs, latex in the OT, synthetic colloid)

Consider differentials for resistant bronchospasm & resistant hypotension
-Ix include TOE/TTE

Resistant hypotension:
continue Adr infusion
Additional fluid bolus
add 2nd vasopressor, consider CVC
NAdr 0.05-0.5mcg/kg/min (3-40microg/min) adult, (paeds 0.1-2microg/kg/min, 0.15mg/kg in 50mL & run @ 2-40mL/hr)
Vasopressin 1-2IU bolus then 2IU/hr infusion adult (paeds 1unit/kg in 50mL, give a 2mL bolus then run @ 1-3mL/hr (0.02-0.06units/kg/hr)
If neither available, can use metaraminol or phenylephrine

For resistant hypoT due to B-blocker, give glucagon 1-2mg IV every 5 min until responsive
for paeds, 40microg/kg IV to a max 1mg

For resistant bronchospasm, continue Adr infusion, check for airway device or circuit malfunction, tension PTx (& decompress)
Can give 12 puffs of salbutamol via MDI or IV bolus 100-200microg +/- infusion 5-25microg/min (paeds 6 puffs MDI if <6yo, 12 puffs if >6yo (100microg/puff))
can give Mg++ 2g (8mmol) over 20 mins (for paeds, use 50% Mg++ (500mg/mL), 50mg/kg (0.1mL/kg) over 20mins (max 2g)
consider inhalation agents & ketamine

For paeds, could also consider aminophylline (10mg/kg over 1 hr (max 500mg) or hydrocortisone (2-4mg/kg, max 200mg)

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10
Q

As part of anaphylaxis “post-crisis management”, which medications could be considered when the pt is haemodynamically stable?

A

steroids (dexamethasone 0.1-0.4mg/kg (paed max 12mg) or hydrocortisone 2-4mg/kg (paed max 200mg) & oral 2nd generation antihistamine (parenteral not recommended) eg. fexofenadine, cetirizine, loratadine

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11
Q

If a pt has had grade III anaphylaxis for an Emerg lap appendicectomy & stabilised, would you proceed? justify…
What postop monitoring is required & what would be the discharge destination? Why?

A

Yes- if pt definitely stable- would ensure senior surgeon operating & would do a coagulation screen if proceeding. NAP6 suggests no bad outcomes if proceed w OT in the immediate post-anaphylaxis situation if the pt has stabilised
The pt needs close monitoring for @ least 6 hrs, recommend ICU for postop monitoring @ least 24hrs if the anaphylaxis was mod-severe (Gd II +), anaphylaxis may persist for >24hrs despite aggressive Rx

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12
Q

What are the rates of cross-reactivity between muscle relaxants?

A

50-60% of ppl who are allergic to one muscle relaxant are allergic to another- it’s usually within the same class.

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13
Q

What is the chance that a pt who’s allergic to penicillin will also be allergic to cephalosporin?

A

1%, 2-3% if anaphylaxis to a penicillin

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14
Q

What’s the chance that a pt with a proven penicillin allergy will be allergic to any antibiotic?

A

1%

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15
Q

Where does clorhex rank among the common causes of anaphylaxis?

A

3rd or 4th

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16
Q

Which commonly used agents in Anaes have a specific IgE test available?

A

Sux, rocuronium, chlorhex & latex
penicillins & some cephalosporins

sIgE testing has low sensitivity & use not routinely indicated

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17
Q

When does tryptase peak after anaphylaxis?

A

15-120mins

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18
Q

What are the signs of severe bronchospasm?

Aside from anaphylaxis, what are some differentials for severe bronchospasm?

A

Wheeze, high airway pressures, difficulty ventilating, dyspnoea/stridor

Circuit malfunction (check using self-inflating bag)

Device malposition/malfunction (check w suction catheter, consider replacing)

Aspiration (consider bronchoscopy)
Foreign body (consider bronchoscopy)
Tension PTx (decompress)

Exac asthma

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19
Q

How is Adrenaline diluted for an infusion? what’s the trick to dosing this for refractory bronchospasm?

A

3mg in 50mL, so 60microg/mL

Infusion rate is 0.1microg/kg/min so for a 70kg person it’s 7mL/hr (the rate in mL/hr=mcg/min)

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20
Q

What’s the adult IV salbutamol dose for refractory bronchospasm? What other drugs can be given?

A

100-200microg IV over 5mins
For infusion, 200microg load over 1 min then 5-25microg/min

Adr infusion
Mg++ 8mmol (2g) over 20mins
Consider inhalation Anaes or ketamine

21
Q

What’s the equation for total tryptase that would be considered clinically significant?

A

> 1.2 x baseline +2

has high PPV and moderate NPV for anaphylaxis

22
Q

How is tryptase required to be stored? What type of tube?

A

if it’ll take >1hr for the sample to get to the lab, needs to be refrigerated so get it to the lab ASAP
Serum (serum separator) or plain tube

23
Q

How is vasopressin prepared?

A

60 units in 60mL N/saline, so 1 unit/mL, 1-2mL/hr= rate for refractory anaphylaxis

24
Q

From what age are the adult anaphylaxis cards relevant?

A

12+

25
Q

What’d be the indications for intubation in paediatric anaphylaxis?

A

would consider it early, any airway oedema, cardiac or resp compromise

26
Q

What are the doses for fluid boluses in paediatric anaphylaxis?

A

20mL/kg crystalloid (ideally warmed)

27
Q

What are differentials for hypotension?

A

Inadequate preload:
-Hypovolaemia/haemorrhage

  • Sepsis
  • Neuraxial blockade

Drug OD

Vasodilation by drugs (eg. Anaes agents)

Vasovagal

Embolism: thrombotic, air, amniotic

pump failure: myocardial ischemia

28
Q

What are differentials for mucocutaneous signs other than anaphylaxis?

A

direct histamine release
cold-induced anaphylaxis
C1 esterase deficiency (angioedema only)
mastocytosis

venous obstruction
head-down position

29
Q

what’s the biological half-life of tryptase? after anaphylaxis, how long does tryptase take to decline?

A

2hrs

peak level 15-120mins after reaction, declines slowly over 3-6hrs, back to baseline 24hrs after reaction (ie. samples are timed to detect the peak & baseline)

30
Q

What are some conditions associated with elevated tryptase in non anaphylactic patients?

A 
systemic mastocytosis
hereditary alpha tryptasemia
AML
myelodysplastic syndromes
severe renal failure
31
Q

What’s the utility of histamine in anaphylaxis?

A

while histamine may be more sensitive than tryptase, the short half-life (2 mins) & difficulty handling samples limits it’s utility for clinical use

32
Q

When is skin testing performed? what meds useful for?

A

4-6 weeks after event (waiting for mast cell histamine to replenish- if testing needs to be performed prior to 4-6/52, only +ve skin tests to be taken into account & may consider repeating testing after 4-6/52.

Any antihistamine the pt is taking stopped for 1/52, corticosteroids, antidepressants & antipsychotics with antihistamine activity may interfere-cease topical corticosteroids at the site antipsychotics &TCA’s generally aren’t ceased but taken into consideration for interpretation)
SPT is useful for NMBAs & crystalloid, not barbiturates, Benzos, opioids; +ve if wheal is at least 3mm greater than negative control (which must be <3mm diameter), read @ 10-15mins.

IDT if clinical suspicion but negative SPT- 4mm bleb of diluted drug injected ID, read @ 15-20 mins, +ve if wheal doubles in size or increases by at least 3mm

32
Q

When is skin testing performed? what meds may interfere?

A

4-6 weeks after event (waiting for mast cell histamine to replenish)
any antihistamine the pt taking (H1 blocker) stopped for 1/52. Corticosteroids, antidepressants & antipsychotics with anti-histamine activity may interfere; cease H2 blockers on the day, cease topical corticosteroids at the site ceased for 1/52, Antipsychotics & TCA’s generally aren’t ceased but taken into consideration for test interpretation. Don’t need to stop leukotriene receptor antagonists or oral/inhaled CS. On the balance, B-blockers & ACE-I’s should be continued.
SPT is useful for NMBAs & crystalloid, not barbiturates, Benzos, opioids; +ve if wheal at least 3mm greater than negative control (which must be at least 3mm diameter), read @ 5-10mins
IDT if clinical suspicion but negative SPT- 4mm bleb of diluted drug injected ID, read @ 15-20 mins, +ve if wheal doubles in size or increases by at least 3mm

33
Q

Define anaphylaxis?

A

severe, potentially fatal, systemic allergic reaction, occurring suddenly after contact with an allergy-causing substance

34
Q

What are the primary tools for identification of immediate hypersensitivity reactions?

A

skin prick testing (SPT) and intra dermal testing (IDT)

Designed to trigger mast cell degranulation, characterised by wheal & flare response

SPT usually used for Ix of food & aeroallergen allergy, NOT useful for delayed hypersensitivity testing

IDT useful for delayed type hypersensitivity due to ability to perform a delayed read

Also, IDT is the most common technique for perioperative allergy testing in Australasia. IDT has greater sensitivity cf SPT and SPT has poor NPV for drug hypersensitivity cf IDT. Generally, use IDT at the outset to minimise false negative skin results. If SPT performed first, should always consider IDT if the SPT was negative.

34
Q

What are the primary tools for identification of immediate hypersensitivity reactions?

A

skin prick testing (SPT) and intra dermal testing (IDT)

Designed to trigger mast cell degranulation, characterised by wheal & flare response

SPT usually used for Ix of food & aeroallergen allergy, NOT useful for delayed hypersensitivity testing

IDT useful for delayed type hypersensitivity due to ability to perform a delayed read

Also, IDT is the most common technique for perioperative allergy testing in Australasia. IDT has greater sensitivity cf SPT and SPT has poor NPV for drug hypersensitivity cf IDT. Generally, use IDT at the outset to minimise false negative skin results. If SPT performed first, should always consider IDT if the SPT was negative.

35
Q

When is skin testing recommended?

A

ALWAYS: when there’s a strong clinical Hx supporting a Dx of periop anaphylaxis

may be considered with less severe immediate hypersensitivity reaction

recommended when there’s acute elevation in serum tryptase contemporaneous with anaphylactic reaction

recommended prior to surgery where suspicion of previously uninvestigated periop anaphylaxis (likely only practical if surgery elective)

35
Q

When is skin testing recommended?

A

ALWAYS: when there’s a strong clinical Hx supporting a Dx of periop anaphylaxis

may be considered with less severe immediate hypersensitivity reaction

recommended when there’s acute elevation in serum tryptase contemporaneous with anaphylactic reaction

recommended prior to surgery where suspicion of previously uninvestigated periop anaphylaxis (likely only practical if surgery elective)

36
Q

contraindications for skin testing?

relative contraindications or precautions?

A

no healthy skin
severe dermatographism
previous severe non-immediate hypersensitivity reaction eg. EM, SJS, TEN, DRESS

recent antihistamines
severe asthma
B-blockers or ACEs
limbs affected by lymphoedema, neurogenic abnormalities, paralysis
pregnancy
37
Q

For how long observe the pt after any skin test?

A

40 mins from commencement

38
Q

Main limitation of sIgE antibody testing?

A

issues with sensitivity & specificity limit their value when used alone, although they can be useful when used in combo with pt Hx & skin test results

39
Q

When is graded challenge testing indicated? Where should it be undertaken?

A

to identify safe agents for use in subsequent anaesthesia- ONLY after -ve skin test

only undertake in centres experienced in allergy Mx & Ix- and minimum facilities (as for skin testing) including ability to administer Adr IM, IVT, supplemental O2 & CPR + assist ventilation

40
Q

Most common cause of periop anaphylaxis in Aust?

A

NMBAs

41
Q

If a pt with anaphylaxis to a NMBA doesn’t show cross-reactivity to other agents on skin testing can they be used freely?

A

False -ves do occur so use any NMBA with caution & if use a particular NMBA safely, add it to the pts documentation

42
Q

What should occur in instance of B-lactam allergy?

A

need to test with at least the exact drug used at the time of reaction

use a SPT initially (including major & minor penicillin determinants, amoxicillin & cephalosporins)

If -ve, SPT followed by IDT with increasing [] to the non-irritating concentration (NIC) to increase sensitivity

There is a risk of false -ve with IDT so allergy to B-lactams can only be excluded with provocation testing with the specific drug from the time of the reaction (positive oral provocation after negative skin test can occur in almost 1/3 of pts!)

43
Q

Is there the possibility of a delayed reaction when a subcutaneous challenge is performed? eg. to a LA? clinical implications?

A

yes, so follow the pt up at 24 hours to Ax for delayed response

44
Q

What are the recommendations regarding steroids and anti-histamines in post-crisis management following suspected anaphylaxis?

A

once situation stabilised, consider steroids: dexamethasone 0.1-0.4mg/kg (paed max 12mg) or hydrocortisone 2-4mg/kg (paed maximum 200mg) or ORAL antihistamines (may be useful for symptomatic Rx of urticaria, angioedema, pruritus; oral non-sedating (eg. loratadine & fexofenidine 2nd gen), IV/IM not recommended)

45
Q

if proceeding with surgery, along with the 1, 4 & 24hr tryptases, what other tests must be sent?

A

coagulation screen

Fellowship revision (78 decks)

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