Transcript Allergy, Anaphylaxis & Immune Reactions Christine Kennedy

Allergy, Anaphylaxis & Immune Reactions
Christine Kennedy & Katharine Smart
Objectives
• Need to cover the basics
– Definition of anaphylaxis
– Types of immune reactions
• Discuss the following allergies:
– antibiotic, venom & Cow’s Milk Protein
• Review the evidence for anaphylaxis meds
• Demonstrate how to use an epi pen
• Review Serum Sickness
Allergy Take Home Points
1. There are 4 types of immune reactions. Type 1
is IgE mediated (ie causes anaphylaxis)
2. Cow’s milk protein allergy is the most common
infant “allergy”
3. Patients with venom allergies should be referred
for venom immunotherapy
4. True antibiotic allergies occur infrequently
-Patients with suspected PCN allergy should be referred for skin testing
-Cephalosporins can generally be safely used in pts with PCN allergies
List the 4 types of immune reactions
Type 2 Hypersensitivity
Type 3 Hypersensitivity
List the 8 most common food allergens
True or False?
• If you delay the introduction of certain foods (ie
peanuts) you will decrease the likelihood that a child
will have an allergy
• If a Mom avoids certain foods in pregnancy, she will
decrease the chance of her child developing an allergy
• If a sibling has a food allergy, the other sibling has an
increased chance of having the allergy
• If someone “smells” an allergen, they can have a
reaction
New onset of “hives”
Mom would like you to
refer her for allergy
testing.
What do you tell her?
Is this the gold standard?
•Parents present to
the ED in distress
•Their 2mo old girl
has bloody stools
CMPA=most common food allergy experienced by infants
Hymenoptera
Venom Immunotherapy
-May reduce the risk of
systemic reaction after a
subsequent sting from
30-60% to <5 %
-Protection may last for
> 20 years
Penicillin is the most common cause of drug anaphylaxis
Occurs in 1/5000 - 1/10,000 courses of Penicillin
Vague=rash, GI sx, unknown rxn
Convincing = anaphylaxis,
angioedema, urticaria, pruritic rash
33% of patients with a + skin test reported a vague history of a
penicillin reaction
Take home message: Patients with vague histories should
undergo PCN skin testing, just as patients with more convincing
histories, prior to repeat doses of PCN
10% Cross Reactivity??
Safe to use cephalosporins in pts with reported allergy to pcn
Retropective cohort of >500,000 patients who received cephaloporins after Penicillin
Of the 534,810pts
-3920 had an allergic reaction to PCN
-624 had an allergic reaction to cephalosporins
25 had anaphylaxis with Penicillin (25/3920, 0.64%)
1/25 had a second anaphylactic reaction with a cephalosporin
Allergic events with cephalosporins are increased with hx of rxn to penicillin
but to a similar degree as those who have had rxns to SMX
-unlikely that rxns are a class effect
• Endorse the use of cephalosporins for patients with
penicillin allergies
– As long as the reaction isn’t severe
• No good evidence to support cross reactivity between PCN’s
and cephalosporins based on class effect alone
• Patients with a true anaphylactic history to penicillin are at
risk of reacting to other abx, not just cephalosporins
• Patients with asthma generally have poorer outcomes
• As Emerg docs we have the advantage of being able to treat
adverse reactions quickly (If in doubt, observe post 1st dose)
Common allergic reactions-delayed
List all the Sulfonamide containing drugs
you can
Antimicrobials
Sulfamethoxazole
Sulfasalazine
Sulfadiazine
Sulfisoxazole
Sulfacetamide
Sulfa Antimicrobial Allergies
8% of patients treated with
SMX have an adverse reaction
– 3% of reactions represent
hypersensitivity
Largest % abx induced cases of TEN
and SJS
Diagnosis?
Allergy Take Home Points
1. There are 4 types of immune reactions. Type 1
is IgE mediated (ie causes anaphylaxis)
2. Cow’s milk protein allergy is the most common
infant “allergy”
3. Patients with venom allergies should be referred
for venom immunotherapy
4. True antibiotic allergies occur infrequently
-Patients with suspected PCN allergy should be referred for skin testing
-Cephalosporins can generally be safely used in pts with PCN allergies
Anaphylaxis Take Home Points
1. Epi 1:1000 0.01mg/kg IM in lateral thigh
2. Antihistamines may provide relief of
cutaneous symptoms
3. Biphasic reactions do occur and
recommendation stands that pts should be
observed for 4-6 hours
4. Know how to counsel patient/family on epi
pen use
What?
Where?
How?
• Failure to administer epinephrine early is the
single most important risk factor for fatal or
near fatal reactions
» Bock, SA J. Allergy Clin Immunol 2001;107:191-3
• “There are no contraindications to the use of epinephrine for a
life-threatening allergic reaction”
– AAAAI board of Directors JACI 1998;102:173-76
14000
12000
10000
[Epi]peak ug/mL
8000
6000
4000
2000
0
Epi Pen IM T
EPI IM T
Epi IM A
Epi SQ A
Ctrl
J Allergy Clin Immunol 2001; 108:871-3
Antihistamines
Antihistamines: Bottom Line
• Should not replace epinephrine in the
management of anaphylaxis
• May alleviate dermatologic symptoms
• May play a role in secondary prevention
before exposure
-Theoretically prevents
biphasic reaction
-Onset 4-6h
-IV methylpred 1-2mg/kg
[max 125mg]
-PO prednisone 1mg/kg
[max 75mg]
Non responders
• Epinephrine infusion
– 0.1-1mcg/kg/minute
• Vasopressin?
-50 yo M with previous
anaphylactic rxn to shellfish
-Presents now with rapidly
progressive mucosal edema,
SOB, bradycardia &
hypotension
PMHx:
– IHD, DMII, HTN
He is on an epi infusion and not getting better. Why? What can you do?
Glucagon Dose
– 1-5 mg IV (20-30 mcg/kg in peds) over 5 min, then
infusion of 5-15 mcg/min (titrated to response)
Summary of Treatment
1.
2.
3.
4.
5.
6.
7.
Epinephrine 0.01 mg/kg IM lat thigh
Diphenhydramine 1 mg/kg IV [50mg]
Ranitidine 1mg/kg IV [50 mg]
Methylprednisone 1-2mg/kg IV [125 mg]
Epi infusion if persistent hypotension
Consider: Glucagon if patient on BB
Consider Ventolin if asthmatic or if patient
continues to struggle
Disposition
• Things to counsel patient/family on
–
–
–
–
–
Biphasic Reactions
Epi-pen usage
When to call 911
Medic alert bracelet
Referral to allergist
Biphasic Anaphylaxis
How common?
3-20% of patients
Who gets it?
No validated clinical predictors
Time Frame?
1-72 hours
Biphasic Reaction: Prospective Study
• 20% had biphasic reactions
• Onset 2-38 hours
• Found an association between time to
resolution of first episode and chance of
recurrence
Biphasic Anaphylaxis
Decisions based on judgment not science
• Observation Period
– Guidelines (CPS) advise observing for 4-6h
• up to 12h if rural environment
– Extra caution with asthmatic patients or pts on BB
– Reliable companion is desirable
– Consider admitting pts: with severe sx, who req’d repeat epi or
who have biphasic reactions
• Discharge Medications
• Epi pen
• Corticosteroids
– No clinical trials to support, but little harm in 3d course
– There are case reports where it didn’t help
• Antihistamines
– No clinical trails to support, may help with cutaneous sx
Common triggers:
Foods and NSAIDS pre/post exercise
Anaphylaxis Take Home Points
1. Epi 1:1000 0.01mg/kg IM in lateral thigh
2. Antihistamines may provide relief of
cutaneous symptoms
3. Biphasic reactions do occur and
recommendation stands that pts should be
observed for 4-6 hours
4. Know how to counsel patient/family on epi
pen use
7 year male
Peri-oral itching after
eating an apple
PMHx: Seasonal hay fever,
no drug or food allergies
17 month female
17 month female
SERUM SICKNESS
Immune Reaction Take Home Point
1. Need to consider serum sickness in a child
with a rash and recent antibiotic use
Objectives
• Need to cover the basics
– Definition of anaphylaxis
– Types of immune reactions
• Discuss the following allergies:
– antibiotic, venom & Cow’s Milk Protein
• Review the evidence for anaphylaxis meds
• Demonstrate how to use an epi pen
• Review Serum Sickness