Anaphylaxis resident survival guide

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Vidit Bhargava, M.B.B.S [2]

Definition

An acute, severe, potentially life threatening type 1 hypersensitivity reaction, following repeated exposure to an allergen to which an individual is already sensitised.

Causes

Life Threatening Causes

Any of the factors precipitating anaphylaxis can be life threatening. The list of substances that cause anaphylaxis is non-exhaustive and it is beyond our scope to mention all. Use caution:

• Food: Peanuts, Tree nuts, walnuts, pecans, milk, soyabean, wheat, eggs, pistachios, filberts, cashews, almonds, etc.
• Shellfish: crab, crayfish, prawns, shrimp, lobster, etc.
• Medications: Penicillin, Sulfa antibiotics, Allopurinol, and many other drugs
• Diagnostic materials: IV contrast material and dyes
• Insect venom: including bees, wasps, ants
• Natural rubber latex
• Idiopathic/ Coital anaphylaxis

Diagnostic Criteria

It is diagnosed with one of the following criteria:
♦ Acute onset of a reaction (mins to hours) involving skin, mucous membrane or both. Additionally including atleast one of the following:

• Respiratory compromise or
• Cardiovascular compromise/Evidence of end organ dysfunction.

♦ 2 or more of the following in a patient known to come in contact with an established allergen:

• Skin/mucosal tissue involvement
• Respiratory compromise
• Reduced blood pressure
• Gastrointestinal manifestations

♦ Reduced blood pressure after exposure to a known allergen.

Management

Shown below is an algorithm summarizing the approach to [[Anaphylaxis]].

Characterize the symptoms & signs: Skin, subcutaneous tissue and mucosa: ❑ Flushing, itching, urticaria, angioedema, rash, piloerection ❑ Periorbital itching, erythema and edema; conjunctival erythema, tearing Respiratory: ❑ Nasal itching, congestion, rhinorrhea, sneezing ❑ Throat itching and tightness, dysphonia, hoarseness, stridor, dry staccato cough ❑ Tachypnea, dyspnea,chest tightness, wheezing/bronchospasm ❑ Cyanosis ❑ Respiratory arrest Gastrointenstinal: ❑ Pain, nausea, vomiting, diarrhea Cardiovascular: ❑ Chest pain, tachycardia, palpitations ❑ Hypotension, feeling faint ❑ shock ❑ Cardiac arrest Central nervous system: ❑ Anxiety, irritability ❑ Throbbing headache ❑ Altered vision and mental status

Consider alternative diagnosis: ❑ Acute asthma ❑ Anxiety/Panic attack ❑ Syncope

Remove patient from exposure/trigger

Do all 3 simultaneously ❑ Call for help ❑ Inject aqueous epinephrine (adrenaline) IM in the mid-anterolateral aspect of the thigh, 0.01 mg/kg of a 1:1,000 (1 mg/mL) solution Maximum dose 0.5 mg (adult) or 0.3 mg (child) Record the time of the dose and repeat it in 5-10 minutes, if needed or ❑ Intravenous epinephrine: In patients with hypotension/cardiorespiratory arrest and those not responding 1:100,000 solution of epinephrine (0.1 mg [1 ml of 1:1000] in 100 ml saline) intravenously by infusion pump at an initial rate of 30-100 ml/hr (5-15 mg/min) Titrate based on clinical response or epinephrine side effects ❑ Place patient on back/comfortable position; elevate legs

Yes

Patient has one of the following? ❑ Respiratory distress ❑ Recieved repeated doses of epinephrine ❑ Asthma/other respiratory disease ❑ Co-existing cardiovascular disease

❑ Give high flow supplemental oxygen (6-8 L/min)

No

Patient hypotensive despite epinephrine?

Yes

No

❑ Establish IV access ❑ Give 1-2 litres of 0.9% saline rapidly, 5-10 ml/Kg in first 5-10 mins ❑ Give vasopressors (dopamine) 400mg in 500ml of 5% dextrose at 2-20 mg/kg/min to maintain a target systolic BP > 90 mm Hg

Secondary therapy after epinephrine (evidence not clear) H1 antihistaminics: ❑ Diphenhydramine IM or slow intravenous infusion - 25 to 50 mg in adults, and 1 mg/kg up to 50 mg in children H2 antihistaminics: ❑ Ranitidine - 1 mg/kg in adults, and 12.5 to 50 mg in children IV or IM

❑ Observe the patient for biphasic anaphylaxis Total period of observation depends on a) clinical condition b) patients access to emergency care setting from home ❑ Provide auto-injectable epinephrine and action plan for future events at discharge

References

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