Anaphylaxis

Debra O’Brien29/8/12

37 yr old man (PMHx Asthma)30 minutes itchy red rash over his chest and abdomenonset while eating dinner in restaurant

When is an allergic reaction considered to be anaphylaxis?

When is an allergic reaction considered to be anaphylaxis?

National Institute of Allergy and Infectious Disease and the Food Allergy and Anaphylaxis Network.

Anaphylaxis is highly likely when any 1 of the following 3 criteria are fulfilled:

1. Acute onset of an illness (minutes to several hours) with involvement of the skin, mucosal tissue, or both (eg, generalized hives, pruritus or flushing, swollen lips-tongue-uvula) AND at least 1 of the following:

Respiratory compromise (eg, dyspnea, wheeze-bronchospasm, stridor, reduced PEF, hypoxemia)Reduced BP or associated symptoms of end-organ dysfunction (eg, hypotonia [collapse], syncope, incontinence)

2. Two or more of the following that occur rapidly after exposure to a likely allergen for that patient (minutes to several hours):

Involvement of the skin-mucosal tissue (eg, generalized hives, itch-flush, swollen lips-tongue-uvula)Respiratory compromise (eg, dyspnea, wheeze-bronchospasm, stridor, reduced PEF, hypoxemia)Reduced BP or associated symptoms (eg, hypotonia [collapse], syncope, incontinence); persistent gastrointestinal

symptoms (eg, crampy abdominal pain, vomiting)

3. Reduced BP after exposure to known allergen for that patient (minutes to several hours):Infants and children: low systolic BP (age specific) or greater than 30% decrease in systolic BPAdults: systolic BP of less than 90 mm Hg or greater than 30% decrease from that person’s baseline

Anaphylaxis

Acute onset multiple-organ hypersensitivity

some degree of skin involvement appears to be nearly universal (although often subtle, such as mild erythema)

PLUS respiratory (throat or chest tightness, breathlessness, wheeze, stridor, hypoxia)

cardiovascular (hypotension, collapse, loss of consciousness)

gastrointestinal (nausea, vomiting, abdominal pain)

What are the common triggers?Venomous stings and bites 30%

Medication (antibiotics, NSAIDs) 22%

Food (nuts, seafood) 18%

Unidentified 25%

Other 5%

What are the common triggers?Venomous stings and bites 30%

Medication (antibiotics, NSAIDs) 22%

Food (nuts, seafood) 18%

Unidentified 25%

Other 5%

When do you give Adrenaline?• “The number one cause of death in anaphylaxis is the failure to

administer adrenaline”Under-recognized and therefore under-treated

• Several case series have implicated the failure to administer adrenaline early in the course of treatment as a consistent finding in anaphylaxis deaths

• Not possible to predict– severity– rate of progress– response to treatment – risk of biphasic or protracted

• Consensus – even mild systemic reactions are best treated immediately with adrenaline → prevent progression to more severe symptoms more effectively than any other available therapies.

• There are NO absolute contraindications to adrenaline use in

anaphylaxis

How much Adrenaline?

Adrenaline 0.01 mg/kg of 1:1000 (1 mg/mL) to a maximum of 0.3-0.5 mg by INTRAMUSCULAR injection

every 3-5 minutes if life-threatening symptoms of hypotension, respiratory distress or stridor persist.

normal saline 10-20mL/kg boluses for persistent hypotension

Adrenaline Infusions

1 mg of adrenaline 1:10,000inject into 1000mL bag of normal salinestart infusion at 1 mL/min (1 µg/min)increase rate until resolution of severe anaphylaxis

Orif you have a central line6mg in 100 mL of 5% Glucose→ 60 µg/mL Start infusion at 1 mL/hr (1 µg/min)

What is the role of antihistamines?

UpToDate and Cochrane ReviewNo evidence to support the use of H1 antihistamines in

anaphylaxis

Adjunctive to relieve itching and hives They DO NOT relieve the other symptoms of anaphylaxis and in standard doses do not inhibit mediator release

• 1st vs 2nd generation antihistamines• H2 antihistamines

What is the role of steroids?UpToDate and Cochrane Review

No evidence to support the use of steroids in anaphylaxis

Adjunctive to prevent the biphasic or protracted reactions occur in up to 23 percent of adults with anaphylaxis, and up to 11 percent of

children with anaphylaxis.

• Methylprednisolone of 1-2mg/kg for 3 days without a taperall biphasic reactions reported to date have occurred within 72 hours• Hydrocortisone 4 mg/kg IV or IM then 2-4mg q6h

What is the role of bronchodilators?

Adjunctive treatment of bronchospasm not responsive to adrenalinedo not prevent or relieve mucosal oedema in the upper airway or shock, for which the alpha-1 adrenergic effects of adrenaline are

required

Should you do any investigations?

Lab tests are not usually required – clinical diagnosis

Helpful when diagnosis of anaphylaxis is unclear

• Total tryptase levels may be tested within 3 hours of symptom onset.– peak tryptase level correlated with severity of symptoms.– normal tryptase levels do not rule out a diagnosis of anaphylaxis, and

are more likely with food-related anaphylaxis

• Histamine levels peak within 10 minutes of onset of anaphylaxis return to baseline within 60 minutes

Which patients need to be admitted?

Admission• Severe anaphylaxis• Mild to Moderate anaphylaxis that does not respond

promptly to adrenalineVs

ObservationFor patients with anaphylaxis which resolves promptly and

completely with treatment → minimum observation period of 4 hours, and prefer a period of 8 to 10 hours, if possible.

What is the risk of a biphasic reactions?

• Occur about 5% of the time• May occur >24 hours after the initial episode• Usually less severe than the initial episode• Possible risk factors include:

1. delayed administration of adrenaline2. slow response to adrenaline3. need for repeated doses of adrenaline4. need for IV fluids

Who needs an Epipen?

The mnemonic "SAFE" - four basic action steps suggested for patients with anaphylaxis who have been treated and are subsequently leaving the emergency department .

• Seek support • Allergen identification and avoidance • Follow-up with specialty care• ‘Epinephrine’ for emergencies

Take Home Messages

• Early recognition

• Early treatment with adrenaline...know your doses!

• Risk of biphasic reactions

• “SAFE”