Managing Anaphylaxis

Managing Anaphylaxis

Guides anaphylaxis recognition using NIAID/FAAN diagnostic criteria, enforces epinephrine-first treatment protocol, and structures observation timing to capture biphasic reactions.

Why This Skill Exists

Anaphylaxis kills approximately 1,500 people annually in the United States, and the majority of deaths are associated with delayed epinephrine administration. Studies consistently show that patients who receive epinephrine within 5 minutes of symptom onset have near-zero mortality, while delays beyond 30 minutes dramatically increase the risk of fatal cardiovascular collapse. Despite this, epinephrine remains underused—only 50-60% of patients presenting with anaphylaxis to EDs receive epinephrine, often because clinicians fail to recognize anaphylaxis without classic urticaria or wait for "more severe" symptoms before acting.

The biphasic reaction rate of 5-20% means observation decisions directly impact patient safety. Premature discharge has resulted in deaths from recurrent anaphylaxis hours after initial resolution. This skill enforces the evidence-based standard: epinephrine is always first-line, antihistamines and steroids are adjuncts only, and observation duration is risk-stratified.

Checkpoint A: Pre-Draft Intake (Mandatory)

1. What was the suspected trigger (food, medication, venom, latex, idiopathic) and time of exposure?
2. What symptoms are present and which organ systems are involved (skin, respiratory, GI, cardiovascular)?
3. Did the patient self-administer epinephrine (auto-injector) before arrival? If so, how many doses, at what times?
4. What is the current hemodynamic status (BP, HR, SpO2, mental status)?
5. Is the airway compromised (stridor, voice change, tongue/lip swelling, inability to swallow)?
6. Does the patient have a history of prior anaphylaxis, asthma, or mast cell disease?
7. Is the patient on beta-blockers or ACE inhibitors (which alter anaphylaxis presentation and treatment response)?
8. For pediatric patients: what is the weight?

Documents to Request

• Pre-hospital records (EMS treatments given, timeline of symptom progression)
• Prior allergy/anaphylaxis documentation and testing
• Medication list (beta-blockers, ACE inhibitors, MAOIs)
• Mast cell disease or mastocytosis history
• Prior epinephrine auto-injector prescriptions and use
• Tryptase level timing documentation (if obtained)
• Vital sign trends from onset through treatment

Step 1: Confirm Anaphylaxis Diagnosis Using NIAID/FAAN Criteria

Anaphylaxis is highly likely when any ONE of these three criteria is met:

Criterion 1: Acute onset (minutes to hours) with skin/mucosal involvement (urticaria, angioedema, flushing, pruritus) PLUS at least one of:

• Respiratory compromise (dyspnea, bronchospasm, stridor, hypoxemia)
• Reduced blood pressure or end-organ dysfunction (syncope, incontinence, collapse)

Criterion 2: Two or more of the following occurring rapidly after exposure to a likely allergen:

• Skin/mucosal involvement (urticaria, angioedema, flushing)
• Respiratory compromise
• Reduced BP or associated symptoms
• Persistent GI symptoms (crampy abdominal pain, vomiting)

Criterion 3: Reduced blood pressure after exposure to a known allergen for that patient:

• Adults: SBP <90 mmHg or >30% decrease from baseline
• Pediatric: age-specific low SBP or >30% decrease

Key point: Anaphylaxis can occur WITHOUT skin findings in 10-20% of cases. Do not wait for urticaria or angioedema to diagnose anaphylaxis if respiratory or cardiovascular symptoms are present.

Step 2: Epinephrine-First Treatment Protocol

Epinephrine Dosing

Repeat dosing: May repeat every 5-15 minutes if symptoms persist or recur. Most patients require 1-2 doses; refractory anaphylaxis may require 3+ doses or IV epinephrine infusion.

Refractory Anaphylaxis (no response to 2-3 IM doses)

1. IV epinephrine infusion: 0.1-1 mcg/kg/min, titrate to hemodynamic response
2. Volume resuscitation: 1-2 L NS rapid bolus for adults (20 mL/kg for children)—anaphylaxis causes distributive shock with up to 35% intravascular volume shift to extravascular space within minutes
3. Glucagon: 1-5 mg IV over 5 minutes for patients on beta-blockers who are epinephrine-resistant (bypasses beta-receptor blockade via direct cAMP activation)
4. Vasopressin: 0.01-0.04 units/min as rescue vasopressor in catecholamine-refractory shock
5. Methylene blue: 1-2 mg/kg IV over 5-20 min for refractory vasoplegia (inhibits nitric oxide-mediated vasodilation)

Step 3: Adjunctive Therapies

These are NOT substitutes for epinephrine and should never delay its administration:

Steroids: Despite widespread use, no randomized controlled trial has demonstrated that corticosteroids prevent biphasic anaphylaxis. However, they remain standard practice in most guidelines pending definitive evidence. Document as "administered per current practice guidelines, evidence pending."

Step 4: Airway Management in Anaphylaxis

Angioedema-related airway compromise is the most common cause of anaphylaxis death:

1. Administer epinephrine immediately—early epinephrine reduces the progression of airway edema
2. Prepare for intubation early if voice change, stridor, or visible tongue/uvula swelling
3. Use the most experienced airway operator available—laryngeal edema distorts anatomy
4. Have surgical airway equipment at bedside (cricothyrotomy kit)
5. Nebulized epinephrine (3-5 mL of 1:1,000) can temporize upper airway edema while preparing for definitive airway
6. Avoid blind nasotracheal intubation in angioedema—risk of hemorrhage into already edematous tissue

Step 5: Observation and Disposition

Risk Factors for Biphasic Reaction

• Severe initial presentation (hypotension, respiratory failure)
• Delayed epinephrine administration (>30 min from onset)
• Prior history of biphasic reactions
• Unknown trigger (cannot confirm allergen avoidance)
• Wide pulse pressure on presentation

Observation Duration Guidelines

Step 6: Discharge Planning

1. Prescribe epinephrine auto-injector (2 devices—one for use, one backup) and ensure affordability
2. Provide written anaphylaxis action plan
3. Refer to allergist/immunologist within 4-6 weeks for trigger identification and potential immunotherapy
4. Educate on trigger avoidance (food label reading, venom avoidance, medication alternatives)
5. Recommend medical alert identification (bracelet or necklace)
6. Document serum tryptase if obtained (draw within 1-3 hours of onset; elevated >11.4 ng/mL supports mast cell degranulation)
7. Address medication conflicts: discuss beta-blocker alternatives with PCP given increased anaphylaxis risk

Checkpoint B: Post-Draft Alignment (Mandatory)

1. Was epinephrine administered as the first-line treatment (not antihistamines or steroids first)?
2. Are the NIAID/FAAN diagnostic criteria explicitly documented showing which criterion was met?
3. Is the observation duration appropriate for the severity of the episode?
4. Was an epinephrine auto-injector prescribed at discharge with demonstration of use?
5. Is allergist referral documented with specific timeframe?

Quality Audit

Guidelines

1. Epinephrine IM in the anterolateral thigh achieves peak plasma levels faster than subcutaneous or deltoid injection—thigh is the only acceptable site
2. Never substitute antihistamines for epinephrine—H1 blockers treat urticaria only; they have zero effect on bronchospasm, laryngeal edema, or cardiovascular collapse
3. IV epinephrine bolus (as opposed to infusion) in a patient with a pulse is dangerous—it can cause fatal arrhythmia; use 1:10,000 concentration in 10-20 mcg increments only if infusion unavailable
4. Biphasic reactions typically occur 4-12 hours after initial episode but have been reported up to 72 hours later—ensure patients understand this risk at discharge
5. Beta-blocker patients may present with paradoxical bradycardia during anaphylaxis and may be epinephrine-resistant; glucagon is the critical rescue medication
6. Exercise-induced anaphylaxis and food-dependent exercise-induced anaphylaxis are distinct entities requiring specific counseling about exercise timing relative to meals
7. Tryptase levels are most useful when compared to a baseline level drawn weeks after the episode; a single elevated level supports but a normal level does not exclude anaphylaxis
8. Mast cell disorders (mastocytosis, MCAS) should be considered in patients with recurrent idiopathic anaphylaxis—baseline tryptase >20 ng/mL warrants hematology referral