There is not one standardized method of treating anaphylaxis as underlying causes and presentation, including severity and symptom involvement, are not uniform. 

Preventing Cardiac Arrest

Below are some useful recommendations for managing severe anaphylaxis that can lead to arrest. There is not refutable evidence, but rather anecdotal and consensus support for these recommendations. 

High Flow Oxygen

Provide oxygen to all anaphylaxis patients and ensure high concentration for those in respiratory distress. Assess saturation of oxyhemoglobin for effect. A low threshold for intubation is required if laryngeal edema or bronchospasm is causing significant respiratory distress. 

Epinephrine

The preferred method of administration is IM injection, as this is easy to administer and provides a rapid rise in blood levels. Any patient with concern for anaphylaxis with hypotension, airway edema, or breathing difficulty should be given IM epinephrine. Typically, this is done at the medial and anterior aspect of the mid-thigh. Patients should be monitored to ensure there is no overdose of epinephrine. For anaphylaxis use

• IM 0.2-0.5 mg at 5-15 minute interval if needed. (Class I, Evidence level C). 
• Autoinjectors are available and provide an adult dose of 0.3 mg and a pediatric dose of 0.15 mg. These are the preferred method of injection due to ease of use and quick administration. (Class I, Evidence level C).
• Be aware that patients on beta-blocking medications are both at increased risk for anaphylaxis and are more likely to have inadequate epinephrine response.

Epinephrine auto-injectors for emergency use.

Subcutaneous administration is not recommended as the onset of action is slower and can delay treatment. 

Diagnose anaphylaxis first

As anaphylaxis is often a life-threatening emergency, this must be diagnosed first for expedient treatment. Only if the clinician is certain that anaphylaxis does not exist should he or she move on to the differential.

Two Steps of EpiPen Self-Injection

Epinephrine IV

• 0.5-0.1 mg IV epinephrine can be used for anaphylactic patients that do not have a cardiac arrest. Patients must be monitored to exclude overdose. (Class I, Evidence level B). If there are severe symptoms, continue infusion can be provided at 5-15 mcg/min. IV fluid administration should also be provided. 
• Epinephrine infusion can also be given initially in those without cardiac arrest (Class IIa, Evidence level C) or in the ROSC setting. (Class IIb, Evidence level C).

Volume Replacement

In anaphylaxis, patients with hypotension administer isotonic crystalloids intravascularly (i.e., normal saline). Bolus with 1-2 L (or higher if indicated) is recommended. This can be titrated to achieve a blood pressure over 90 m Hg. Monitor for adverse events such as pulmonary edema. 

Other Therapies

While no strong data is evaluating other therapies for anaphylaxis, there are anecdotal benefits to these adjunct treatments. These therapies: antihistamines (H1 or H2 antagonists), inhaled beta-adrenergic agonists, and IV steroids can be used in anaphylaxis as well as considered in associated cardiac arrest. (Class IIb, Evidence level C). 

Antihistamines

IV and IM antihistamines can be administered at a slow rate. Examples include 25-50 mg diphenhydramine or 300mg cimetidine (PO, IM or IV)

Inhaled beta-adrenergic agonists

Inhaled albuterol can manage bronchospasm. Inhaled ipratropium bromide can be used, especially if the patient uses beta-blocking medications. As there can be clinical ambiguity between severe asthma and anaphylaxis, incorrectly diagnoses anaphylactic patients have been treated with bronchodilation instead of epinephrine. 

Corticosteroids

IV corticosteroids can be used at the onset of treatment as the onset of action is delayed and may be 4-6 hours after administration. 

Potential Treatments

Other treatments may be added, although there is little research supporting their use. 

• Vasopressin: case reports suggest benefit in severe hypotension. It can be considered in associated cardiac arrest. 
• Alpha-adrenergic agonists: case reports suggest benefits with alpha-adrenergic medications, including methoxamine, norepinephrine, and metaraminol. They can be considered in associated cardiac arrest. 
• Atropine: case reports suggest benefits in severe bradycardia
• Glucagon: can be used when epinephrine is unsuccessful and in patients on beta-blocking medications. It has a short time of action, and side effects include emesis, nausea, and hyperglycemia. 

Post-Anaphylaxis Treatment

Following acute treatment, patients should be monitored closely. As many as 20% of patients will have recurrent symptoms within 8 hours and as long as 36 hours. Typically, a four hour observation period is recommended.