eMedicine Specialties > Emergency Medicine > Allergy & Immunology

Anaphylaxis: Follow-up

Author: Richard S Krause, MD, Senior Faculty, Department of Emergency Medicine, State University of New York at Buffalo School of Medicine
Contributor Information and Disclosures

Updated: Sep 2, 2009

Follow-up

Further Inpatient Care

• Most patients with anaphylaxis may be treated successfully in the ED and then discharged. Treatment success operationally may be defined as complete resolution of symptoms followed by a short period of observation. The purpose of observation is to monitor for recurrence of symptoms (ie, biphasic anaphylaxis).
• Hospital admission is required for patients who (1) fail to respond fully, (2) have a recurrent reaction or a secondary complication (eg, myocardial ischemia), (3) experience a significant injury from syncope, or (4) need intubation. As with many other conditions, consider a lower admission threshold when patients are at age extremes or when they have significant comorbid illness.
• The presenting manifestation(s) of anaphylaxis dictate inpatient care. Essentially, this care consists of continuing the care initiated in the ED.
• Consider ICU admission for patients with persistent hypotension. The primary means of support are adrenergic agents (eg, epinephrine, dopamine) and fluid resuscitation. Persistent hypotension in the face of pressors and fluid resuscitation is an indication for invasive hemodynamic monitoring with evaluation of cardiac function and peripheral vascular resistance. Use of these parameters provides the basis for objective decisions regarding the use of fluids and pressors.
• Inpatient management of airway compromise consists of continuation of parenteral and inhaled adrenergic agents and corticosteroids that were initiated in the ED.
• Cutaneous manifestations of anaphylaxis are treated with repeated doses of antihistamines.

Further Outpatient Care

• Discharged patients who have been successfully treated for anaphylaxis usually should continue antihistamines for 2-5 days to prevent recurrence. When corticosteroids have been used as part of the initial treatment, common practice continues that treatment for a short period.

Inpatient & Outpatient Medications

• Inpatient medications are identical to those listed for ED care (see Medication).
• Outpatient medications
  • Outpatient medications primarily consist of oral forms of the medications used in ED treatment. Adrenergic medications are not listed in this chapter, as it is assumed that patients who require these on an on-going basis will be admitted.
  • Consider patients who experience severe reactions to bites, stings, food, or other possibly unavoidable causes, as candidates for an epinephrine auto-injector prescription. These injectors may be packaged as kits that also contain an oral antihistamine.
  • The following regimens are used commonly by clinicians, though very little hard data concerning the natural history of anaphylaxis treated in the ED exists. In light of this, do not construe the following as an unqualified recommendation or as a standard of care. Evidence for efficacy of H2-blocker antihistamines is particularly sparse. The newer nonsedating antihistamines have not been studied in the context of treatment for anaphylaxis.
  • H1-blocker antihistamines
    • Diphenhydramine (Benadryl) - Adults: 25 mg PO q6h for 2-5 d; Children: 1 mg/kg PO q6h for 2-5 d
    • Hydroxyzine (Atarax) - Adults: 25 mg PO q8h for 2-5 d; Children: 1 mg/kg PO q8h for 2-5 d
  • Corticosteroids
    • Prednisone - Adults: 20-80 mg PO qd for 2-5 d; Children: 1-2 mg/kg PO qd for 2-5 d
    • Many other glucocorticoid preparations may be used.
  • H2-blocker antihistamines
    • Cimetidine - 300 mg PO qid for 2-5 d; Children: Not recommended
    • Epinephrine auto-injectors prefilled syringes: A number of forms are available. Instructions for self-administration are included.
    • Ana-Kit (Bayer): This product is a syringe with 0.3 mL 1:1000 epinephrine solution packaged with four 2-mg chewable chlorpheniramine tablets. The syringe has 0.1 mL gradations, allowing the injection of smaller doses for pediatric patients.
    • EpiPen and EpiPen Jr. Auto-Injector (Center): This product is an auto-injecting syringe containing 0.3 mL 1:1000 epinephrine solution (EpiPen) or 0.3 mL 1:2000 solution (EpiPen Jr).

Transfer

• Requirements for treating a patient with anaphylaxis are likely to exist in most hospitals within the United States and Canada; therefore, transfer of patients with anaphylaxis would be a very unusual occurrence in these locations.

Deterrence/Prevention

• Preventive therapy for anaphylaxis depends on identification of the inciting agent. When the agent has been identified, the key to prevention is avoidance. Certain prophylactic or preventative therapies may be employed when re-exposure cannot be avoided. When the inciting agent is not obviously known from the history, allergy testing may help identify it. When the allergen is a therapeutic agent for which subsequent usage is medically necessary, desensitization or pretreatment protocols may be employed.
  • Desensitization therapy for reactions to Hymenoptera venom is partially effective in preventing or ameliorating subsequent severe reactions.
  • At minimum, patients discharged from the ED after a severe reaction to Hymenoptera venom should be informed of the availability of this treatment. Referral to the patient's primary care source or directly to an allergist also may be appropriate.

Complications

• Complications from anaphylaxis are rare, and most patients completely recover. Myocardial ischemia may result from hypotension and hypoxia, particularly when underlying coronary artery disease exists. Ischemia or arrhythmias may result from treatment with pressors. Prolonged hypoxia also may cause brain injury. At times, a fall or other injury may occur when anaphylaxis leads to syncope.

Prognosis

• Anaphylaxis may occur following re-exposure to the inciting agent. Rates of recurrence vary with the nature of the inciting agent and host factors. Other than the possibility of recurrence or the occurrence of complications, anaphylaxis carries no long-term effects.

Patient Education

• As described above, caution patients who are discharged after an episode of anaphylaxis to avoid exposure to an inciting agent. When no inciting agent has been identified, consider referral to an allergist to identify the cause of anaphylaxis.
• Inform patients who react to Hymenoptera venom of the availability of desensitization therapy, and consider a self-administered epinephrine prescription.
• Sting avoidance is important for hypersensitive persons. Patients must be educated concerning steps they can take to reduce the risk of insect stings.
  • Caution patients to avoid use of perfumes or hygiene products that include perfumes, particularly floral scents, as these attract flying Hymenoptera.
  • Brightly colored clothing attracts bees and other pollinating insects.
  • Avoid locations of known hives or nests, and avoid using equipment that disturbs the hive.
  • Persons who are sensitive to Hymenoptera and who must be outdoors should carry a sting kit.
• On discharge, warn patients of the possibility of recurrent symptoms, and instruct them to seek further care if this occurs.
• For excellent patient education resources, visit eMedicine's Allergy Center and Allergic Reaction and Anaphylactic Shock Center. Also, see eMedicine's patient education article Severe Allergic Reaction (Anaphylactic Shock).

Miscellaneous

Medicolegal Pitfalls

• Claims of medical negligence related to the emergency treatment of anaphylaxis are not common. Potential pitfalls are as follows:
  • Failure to consider the diagnosis in patients with unexplained syncope or shock
  • Failure to warn the patient of avoidance or preventive measures
  • Prescription or administration of a drug to which the patient is known allergic
  • Failure to appreciate the potentially serious nature of symptoms, such as syncope or throat tightness, in a patient with an allergic reaction
  • Complications of epinephrine administration in patients without clear indication

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