What is the treatment for anaphylactic shock?

Treatment of Anaphylactic Shock

Immediately administer intramuscular epinephrine 0.3-0.5 mg (1:1000 concentration) into the anterolateral thigh as the first-line, life-saving treatment for anaphylactic shock. 1, 2, 3, 4

Immediate First-Line Treatment

Epinephrine Administration (Primary Treatment)

• Administer IM epinephrine 0.3-0.5 mg (1:1000 concentration) for adults or 0.01 mg/kg for children into the anterolateral thigh immediately upon recognition of anaphylaxis 1, 3, 4
• Repeat the dose every 5-15 minutes as needed if symptoms persist or recur 2, 3
• Between 7-18% of patients require more than one dose of epinephrine 1
• Epinephrine is the only medication with life-saving effects across multiple organ systems, preventing and relieving airway obstruction and shock 5

Patient Positioning and Oxygen

• Position the patient supine with legs elevated (unless respiratory distress prevents this position) 3
• Provide supplemental oxygen and monitor oxygen saturation continuously 3

Activate Emergency Response

• Call emergency medical services (EMS) immediately, even if epinephrine is administered 1
• Approximately 500-1000 people die annually in the United States from anaphylaxis, and patients may require advanced interventions including intubation, IV fluids, and vasopressors 1

Advanced Treatment for Severe or Refractory Cases

IV Epinephrine (When IM Fails or Shock is Profound)

• If IV access is already established and the patient has profound hypotension unresponsive to IM epinephrine and IV fluids, administer IV epinephrine 0.05-0.1 mg (1:10,000 concentration) slowly over several minutes 2, 3
• This represents only 5-10% of the cardiac arrest dose to minimize adverse cardiovascular effects 2
• For persistent hypotension, consider continuous epinephrine infusion at 5-15 μg/min 2, 3
• Continuous hemodynamic monitoring is mandatory when administering IV epinephrine 2

Fluid Resuscitation

• Establish IV access and administer crystalloid bolus: 500-1000 mL for adults or 20 mL/kg for children 3
• Anaphylactic shock can cause up to 37% reduction in circulating blood volume due to vasodilation and increased capillary permeability 6

Monitoring Requirements

• Monitor vital signs continuously: blood pressure, heart rate, respiratory rate, and oxygen saturation 3
• Use every-minute blood pressure measurements and continuous pulse monitoring in settings without advanced monitoring 2

Adjunctive Treatments (Second-Line)

Antihistamines

• Administer H1 antihistamine: diphenhydramine 25-50 mg IV/IM (1-2 mg/kg for children) 3
• Consider H2 antihistamine: ranitidine 50 mg IV for adults (1 mg/kg for children) 3

Corticosteroids

• Consider methylprednisolone 1-2 mg/kg/day IV or prednisone 0.5 mg/kg orally to prevent biphasic reactions 3
• These provide no acute benefit but may prevent late-phase reactions 3

Bronchodilators

• If bronchospasm persists despite epinephrine, administer albuterol nebulization 2.5-5 mg in 3 mL saline 3

Special Clinical Situations

Patients on Beta-Blockers

• If the patient is unresponsive to epinephrine and takes beta-blockers, administer glucagon 1-5 mg IV over 5 minutes, followed by infusion of 5-15 μg/min 2, 3
• Beta-blockade can prevent epinephrine's therapeutic effects 3

Refractory Hypotension

• Consider alternative vasopressors such as dopamine 2-20 μg/kg/min if hypotension persists despite epinephrine 2
• Vasopressin has been reported successful in case reports of severe refractory anaphylactic shock 7

Cardiac Arrest from Anaphylaxis

• Perform standard CPR and advanced life support 3
• Administer high-dose epinephrine IV: 1-3 mg (1:10,000) slowly over 3 minutes, followed by 3-5 mg over 3 minutes, then infusion of 4-10 μg/min 3

Critical Pitfalls to Avoid

• Never delay epinephrine administration while focusing on antihistamines or steroids—these are adjunctive only 2, 8
• Do not administer IV epinephrine too rapidly, as this increases risk of lethal arrhythmias and severe hypertension 2
• Never confuse epinephrine concentrations: use 1:1000 (1 mg/mL) for IM and 1:10,000 (0.1 mg/mL) for IV administration 2
• Avoid subcutaneous epinephrine as it has delayed onset compared to IM administration 5
• Do not use vasodilators like isosorbide, which will worsen the hypotension 6

Observation and Discharge Planning

• Observe patients for at least 6 hours or until stable and symptoms have resolved 3
• Observation periods should be individualized as biphasic reactions are unpredictable and may occur outside typical observation windows 3, 8
• Prescribe an epinephrine autoinjector and provide education on its use before discharge 3
• Provide instructions on allergen avoidance and consider allergy/immunology referral 9