What is the immediate management of anaphylactic shock in an adult patient?

Immediate Management of Anaphylactic Shock in Adults

Administer intramuscular epinephrine 0.3–0.5 mg (1:1000 concentration) into the anterolateral thigh immediately—this is the only first-line treatment that prevents death from anaphylaxis and must never be delayed. 1, 2

First-Line Treatment: Intramuscular Epinephrine

• Inject 0.3–0.5 mg of 1:1000 epinephrine (0.3–0.5 mL) intramuscularly into the vastus lateralis (anterolateral thigh) as this route achieves faster and higher plasma levels than subcutaneous or deltoid injection. 3, 4

• Repeat the same dose every 5–15 minutes if symptoms persist, progress, or recur—there is no maximum number of doses. 3, 2

• Activate emergency medical services immediately upon recognition of anaphylaxis, as patients may require advanced interventions including intubation, IV fluids, and vasopressors. 1, 2

• There are no absolute contraindications to epinephrine in anaphylaxis, even in elderly patients with cardiac disease, as the benefits outweigh risks. 3, 2

Critical Positioning and Monitoring

• Position the patient supine with legs elevated (unless respiratory distress prevents this) to improve venous return in hypotensive shock. 1, 4

• Begin close hemodynamic monitoring immediately after epinephrine administration, as cardiovascular and respiratory status can deteriorate rapidly. 1

• Prepare for emergency airway management by triaging to a provider with advanced airway expertise, given the risk of rapid oropharyngeal or laryngeal edema that may make conventional intubation impossible. 1

Aggressive Fluid Resuscitation

• Administer rapid crystalloid boluses (1–2 liters of normal saline or lactated Ringer's solution in adults) via large-bore IV to counteract vasodilation and capillary leak, which can cause up to 37% loss of circulating blood volume. 3, 4, 2

• Repeat fluid boluses if hypotension persists despite initial resuscitation. 3

Refractory Anaphylactic Shock Management

When to Escalate to IV Epinephrine

• Consider IV epinephrine only when IM epinephrine has failed after 2–3 doses, in profound hypotension unresponsive to IV fluids, or during cardiac arrest from anaphylaxis. 1, 2

• Administer IV epinephrine 0.05–0.1 mg (50–100 mcg) of 1:10,000 concentration slowly over several minutes, with repeat doses as needed—never confuse concentrations (1:1000 for IM, 1:10,000 for IV). 1, 4, 2

• For ongoing refractory shock, start an IV epinephrine infusion at 5–15 mcg/min and titrate to clinical response. 1, 4

Alternative Vasopressors

• Consider dopamine 2–20 mcg/kg/min, norepinephrine, vasopressin, phenylephrine, or metaraminol for persistent hypotension despite epinephrine and fluids. 4, 2

Adjunctive Therapies (Second-Line Only—No Acute Benefit)

Critical caveat: Second-line agents provide no acute benefit and must never delay epinephrine administration. 1

Antihistamines (For Cutaneous Symptoms Only)

• Administer diphenhydramine 25–50 mg IV/IM after epinephrine has been given first. 3, 1, 4

• Consider adding ranitidine 50 mg IV (or famotidine 20 mg IV) as the combination of H1 + H2 antagonists is superior to H1 antagonist alone for cutaneous symptom control. 3, 1, 4

Bronchodilators (For Persistent Bronchospasm)

• Administer albuterol 2.5–5 mg nebulized for bronchospasm that persists despite adequate epinephrine. 3, 4, 2

Corticosteroids (No Acute Benefit)

• Corticosteroids have no proven benefit in acute management of anaphylaxis or cardiac arrest caused by anaphylaxis. 1

• Consider methylprednisolone 1–2 mg/kg IV (typically 40 mg IV every 6 hours for a 70 kg adult) only to potentially prevent biphasic or protracted reactions, though evidence is limited. 3, 1, 4

Special Populations: Patients on Beta-Blockers

• If the patient is taking a beta-blocker and remains refractory to multiple doses of epinephrine, administer glucagon 1–5 mg IV over 5 minutes, followed by continuous infusion at 5–15 mcg/min. 3, 1, 4

• Glucagon is a second-line agent reserved exclusively for beta-blocker patients with refractory anaphylaxis—it should never replace or delay epinephrine administration. 1

Cardiac Arrest from Anaphylaxis

• Implement standard BLS/ACLS protocols immediately with epinephrine as the priority intervention. 1, 2

• Administer high-dose IV epinephrine: 1–3 mg (1:10,000) slowly over 3 minutes, then 3–5 mg over 3 minutes, followed by 4–10 mcg/min infusion. 1, 4

• Antihistamines, inhaled β-agonists, and IV corticosteroids have no demonstrated benefit during cardiac arrest secondary to anaphylaxis. 1

Observation Period and Biphasic Reactions

• Observe all patients for a minimum of 4–6 hours in a monitored area or until stable and symptoms are regressing, as 17% experience delayed deterioration. 4, 2

• Extend observation up to 24 hours for severe reactions, delayed epinephrine administration, history of biphasic reactions, or patients requiring >1 dose of epinephrine. 3, 2

• Biphasic anaphylactic reactions occur in 7–18% of cases and are unpredictable, often manifesting beyond typical observation periods. 1

Discharge Requirements

• Prescribe two epinephrine autoinjectors (0.3 mg for adults ≥30 kg) with hands-on training. 1, 4

• Provide a written, personalized anaphylaxis emergency action plan with trigger identification and clear instructions. 4

• Prescribe prednisone 1 mg/kg daily (maximum 60–80 mg) for 2–3 days without tapering, along with H1 and H2 antihistamines for 2–3 days. 1

• Refer to an allergist within 1–2 weeks for formal allergy testing and long-term management plan. 1

Critical Pitfalls to Avoid

• Never delay epinephrine while administering antihistamines or steroids—this is the most common fatal error. 2, 5

• Do not use subcutaneous epinephrine, as absorption is slower and less reliable than IM. 2, 6

• Do not administer IV epinephrine too rapidly, as this can cause lethal arrhythmias—continuous cardiac monitoring is mandatory during IV administration. 1, 2

• Do not discharge patients prematurely, especially those with airway involvement or requiring multiple epinephrine doses. 1