The incidence of anaphylaxis is rising in the US, the UK, and Australia, particularly among young children.1 This article will review the core principles for treating acute anaphylaxis in the healthcare setting.
Treatment of acute anaphylaxis is centered on prompt administration of epinephrine (also known as adrenaline) as soon as anaphylaxis is suspected.2The preferred route is intramuscular injection of a 1 mg/mL (1:1000) solution in the anterolateral thigh, which leads to more rapid achievement of peak blood concentration than injections at other sites.2
The American Academy of Allergy, Asthma & Immunology (AAAAI) and the American College of Allergy, Asthma & Immunology (ACAAI) recommend a dose of 0.2 to 0.5 mg (0.2 mL to 0.5 mL) for adults and 0.01 mg/kg for children.2 The usual dosage in children under 6 years of age is 0.1 to 0.3 mL. Dosing recommendations by other experts may vary slightly.3 Extra care should be taken in patients with cardiac disease. In healthcare settings, epinephrine may be administered with a syringe or with the same type of epinephrine auto-injector used in community settings, every 5 to 15 minutes as needed.2,3
Intravenous administration may be considered for patients in shock or vascular collapse who have not responded to intramuscular epinephrine.2 Care must be taken, however, to administer a diluted concentration appropriate for intravenous administration in order to avoid overdose. Dilute 1.0 mL (1:1000) in 9 mL of normal saline (final dilution, 1:10,000). Administer intravenously very slowly over 5 to 10 minutes. A too-rapid injection can cause cardiac arrest. The dose can be repeated in 5 to 15 minutes.
Patients taking beta blockers may exhibit a blunted response to epinephrine given for anaphylaxis.2,3 Additional treatments may be necessary, such as glucagon, atropine, or ipratropium.3
Supportive measures for anaphylaxis include supplemental oxygen, intravenous saline, and positioning the patient in a supine position with legs elevated. Intubation and cardiopulmonary resuscitation may be required in severe cases. H1 and H2 antihistamines are useful for controlling cutaneous symptoms. Glucocorticoids may prevent biphasic or protracted anaphylaxis, but the evidence is inconclusive.4 Most importantly, antihistamines and glucocorticoids are considered second-line agents and do not replace epinephrine as the initial treatment of acute anaphylaxis.2,3
Note that a thready or absent pulse suggests low blood pressure or vascular collapse. Aggressive therapy should continue. A patient in impending shock is very alert and aware of his or her surroundings and experiences a sense of doom. Avoid negative comments. A positive attitude and continuous reassurance are important.
After the initial episode has resolved, patients are at risk for a second phase of anaphylaxis, even without re-exposure to the allergen or inciting agent. The incidence of this biphasic reaction ranges from 1% to 20% in the literature.4 The patient should be observed in the healthcare setting, but there are no universal recommendations as to the duration of observation.2-4
“The major factor that typically determines the length of observation is the severity of the reaction,” reports Pratik Doshi, MD, Assistant Professor of Emergency Medicine at UTHealth Medical School, in Houston. “For patients with severe reactions, the goal is for them to be admitted for observation either in the critical care setting or inpatient setting.” Dr. Doshi said that patients with minor episodes would typically be observed “in the emergency department for approximately 6 hours after initial treatment of anaphylaxis.”
Nnaemeka Okafor, MD, MS—also Assistant Professor of Emergency Medicine at UTHealth Medical School—described other factors that influence how long a patient is observed. For example, successful identification of the allergic reaction trigger and assurance that the trigger is no longer present would play a role in determining the length of observation.
Upon discharge from the healthcare setting, the following arrangements should be made to maximize patient safety2,3:
- The patient should be monitored by a responsible individual at home.
- Consultation with an allergist or immunologist is recommended if not yet done.
At least 2 doses of an epinephrine auto-injector should be provided or prescribed, along with instructions for use. The recommendation for multiple doses of the auto-injector is supported by findings that as many as 12% of children with food-related anaphylaxis who receive epinephrine in the emergency department will require a second dose for treatment of the acute episode.5
- A personalized, written anaphylaxis emergency action plan is also beneficial, as well as some sort of medical identification, such as a wallet card or bracelet, which lists the patient’s known allergies.
- The medical record should be prominently flagged to display the anaphylaxis risk and the relevant triggers.
In summary, intramuscular epinephrine is the drug of choice for acute anaphylaxis. Other therapies are supportive, but do not supplant epinephrine as the first-line agent. Close observation after resolution of the initial episode is necessary due to the risk for biphasic anaphylaxis.
Published: 03/20/2013
References:
- Koplin JJ, Martin PE, Allen KJ. An update on epidemiology of anaphylaxis in children and adults. Curr Opin Allergy Clin Immunol. 2011;11:492-496.
- Lieberman P, Nicklas RA, Oppenheimer J, et al. The diagnosis and management of anaphylaxis practice parameter: 2010 update. J Allergy Clin Immunol. 2010;126:477-480.
- Simons FE, Sheikh A. Anaphylaxis: the acute episode and beyond. BMJ. 2013;346:f602.
- Lieberman P. Biphasic anaphylactic reactions. Ann Allergy Asthma Immunol. 2005;95:217-226.
- Rudders SA, Banerji A, Corel B, et al. Multicenter study of repeat epinephrine treatments for food-related anaphylaxis. Pediatrics. 2010;125:e711-e718.
Không có nhận xét nào:
Đăng nhận xét