Anaphylactic Shock Treatment Algorithm

Immediate First-Line Treatment

The American Academy of Allergy, Asthma, and Immunology recommends intramuscular epinephrine 0.01 mg/kg (maximum 0.5 mg adults, 0.3 mg children) of 1:1000 solution injected into the anterolateral thigh as the immediate first-line treatment for anaphylactic shock, which must be administered without delay 1, 2
Administering IM epinephrine immediately upon recognition of anaphylaxis is crucial, as delays in administration are a risk factor for fatal outcomes 1, 2
The American Heart Association recommends activating emergency medical services (EMS) immediately, as patients may require advanced interventions including intubation, IV fluids, and vasopressors 2

Positioning the patient supine with legs elevated can improve venous return in hypotensive shock 3
Approximately 7-18% of patients require more than one dose of epinephrine 2

The American Academy of Allergy, Asthma, and Immunology recommends repeating IM epinephrine every 5-15 minutes if symptoms persist or worsen 1, 2, 4
If EMS arrival will exceed 5-10 minutes and the patient has not responded to the initial dose, administering a second dose is recommended 2

IV epinephrine should only be used when IM epinephrine has failed after multiple doses, in profound hypotension unresponsive to IV fluids, or during cardiac arrest from anaphylaxis 4, 3
The initial dose of IV epinephrine is 0.05-0.1 mg (50-100 mcg) of 1:10,000 concentration, administered slowly over several minutes 3

Aggressive IV fluid boluses are mandatory, as anaphylactic shock can cause up to 37% loss of circulating blood volume due to capillary leak 5
Administering 1-2 liters of normal saline rapidly in adults (20 mL/kg boluses in children) is recommended 4
Diphenhydramine 1-2 mg/kg (25-50 mg in adults) IV or IM, and ranitidine 1 mg/kg IV (or cimetidine 4 mg/kg) can be used as adjunctive therapies 4
Albuterol 2.5-5 mg nebulized can be used for bronchospasm resistant to epinephrine 4
Methylprednisolone 1-2 mg/kg/day IV every 6 hours (or prednisone 0.5 mg/kg PO for less severe cases) can be used to prevent biphasic or protracted reactions, but has no acute benefit 1, 4

Glucagon 1-5 mg IV over 5 minutes (20-30 mcg/kg in children, max 1 mg) followed by infusion at 5-15 mcg/min can be used in patients on beta-blocker therapy 4, 3
Dopamine 400 mg in 500 mL D5W at 2-20 mcg/kg/min, titrated to blood pressure with continuous monitoring, can be used for refractory hypotension 4, 3
High-dose IV epinephrine (1-3 mg) can be used in cardiac arrest from anaphylaxis, with pediatric dosing of 0.01 mg/kg (0.1 mL/kg of 1:10,000) every 3-5 minutes, escalating to 0.1-0.2 mg/kg for refractory arrest 4

A minimum 4-6 hours observation in the emergency department is recommended for all patients, as 17% experience delayed deterioration 1
Extended observation (up to 24 hours) is recommended for severe reactions, delayed epinephrine administration, or history of biphasic reactions 1

Never delay epinephrine while administering antihistamines or steroids, as this is the most common fatal error 1, 2
Do not use subcutaneous epinephrine, as absorption is slower and less reliable than IM 1
Do not administer IV epinephrine too rapidly, as this can cause lethal arrhythmias 3
Never confuse concentrations, using 1:1000 (1 mg/mL) for IM and 1:10,000 (0.1 mg/mL) for IV 3
Do not use vasodilators like isosorbide, which worsen hypotension in anaphylactic shock 5
There are no absolute contraindications to epinephrine in anaphylaxis, even in elderly patients with cardiac disease, as the benefits outweigh risks 1