Hereditary Angioedema

Hereditary angioedema (HAE) is a rare autosomal dominant genetic disorder that usual results from a decreased level of functional C1-INH and clinically manifests with intermittent attacks of swelling of the subcutaneous tissue or submucosal layers of the respiratory or gastrointestinal tracts. Laboratory studies and radiographic imaging have limited roles in evaluation of patients with acute attacks of HAE except when the diagnosis is uncertain and other processes must be ruled out. Treatment begins with assessment of the airway to determine the need for immediate intervention. Emergency physicians should understand the pathophysiology of HAE to help guide management decisions.

Hereditary Angioedema

Hereditary angioedema (HAE) is a rare autosomal dominant genetic disorder that usual results from a decreased level of functional C1-INH and clinically manifests with intermittent attacks of swelling of the subcutaneous tissue or submucosal layers of the respiratory or gastrointestinal tracts. Laboratory studies and radiographic imaging have limited roles in evaluation of patients with acute attacks of HAE except when the diagnosis is uncertain and other processes must be ruled out. Treatment begins with assessment of the airway to determine the need for immediate intervention. Emergency physicians should understand the pathophysiology of HAE to help guide management decisions.

Effectiveness of ecallantide in treating angiotensin-converting enzyme inhibitor-induced angioedema in the emergency department

BACKGROUND

Angiotensin-converting enzyme inhibitor-induced angioedema (ACEI-AE) is mediated by bradykinin. There remains an unmet treatment need because these patients, when presenting to the emergency department (ED), do not respond to conventional therapies, such as antihistamines and corticosteroids.

OBJECTIVE

To estimate the treatment effect of ecallantide, a recombinant plasma kallikrein inhibitor, in ED patients with ACEI-AE in whom conventional therapy fails.

METHODS

This was a triple-blind (patient, physician, and statistician), randomized, controlled, phase 2 study to estimate the magnitude of safety and efficacy signals for designing a definitive phase 3 trial comparing conventional therapy with ecallantide to conventional therapy with placebo. Patients were enrolled from April 1, 2010, through January 31, 2013. The primary efficacy study end point was achieving discharge criteria from the ED within 4 hours after initiating study-related treatment.

RESULTS

Discharge criteria from the ED was met in 4 hours or less for 8 (31%) of 26 patients receiving ecallantide vs 5 of (21%) 24 patients receiving placebo (difference in proportions, 10%; 95% confidence interval, -14% to 34%). Ecallantide was well tolerated in both groups.

CONCLUSION

The results from this preliminary study reveal that ecallantide is safe to use and may increase the proportion of patients who meet early discharge criteria by approximately10%. A larger phase 3 study is necessary to confirm the efficacy and evaluate the cost-effectiveness of ecallantide use for ACEI-AE in the ED setting.

TRIAL REGISTRATION

clinicaltrials.gov Identifier: NCT01036659.

A consensus parameter for the evaluation and management of angioedema in the emergency department

Despite its relatively common occurrence and life-threatening potential, the management of angioedema in the emergency department (ED) is lacking in terms of a structured approach. It is paramount to distinguish the different etiologies of angioedema from one another and more specifically differentiate histaminergic-mediated angioedema from bradykinin-mediated angioedema, especially in lieu of the more novel treatments that have recently become available for bradykinin-mediated angioedema. With this background in mind, this consensus parameter for the evaluation and management of angioedema attempts to provide a working framework for emergency physicians (EPs) in approaching the patient with angioedema in terms of diagnosis and management in the ED. This consensus parameter was developed from a collaborative effort among a group of EPs and leading allergists with expertise in angioedema. After rigorous debate, review of the literature, and expert opinion, the following consensus guideline document was created. The document has been endorsed by the American College of Allergy, Asthma & Immunology (ACAAI) and the Society for Academic Emergency Medicine (SAEM).

Diagnosis and management of hereditary angioedema: an emergency medicine perspective

BACKGROUND

Hereditary angioedema (HAE) is a rare and often debilitating condition associated with substantial morbidity and mortality in the absence of appropriate intervention. An underlying deficiency in functional C1-inhibitor (C1-INH) protein induces a vulnerability to unchecked activation of the complement, contact, and coagulation/fibrinolytic systems. The clinical consequence is a pattern of recurring attacks of non-pitting, non-pruritic edema, the urgency of which varies by the affected site. Laryngeal edema can escalate rapidly to asphyxiation, and severe cases of abdominal swelling can lead to hypovolemic shock.

OBJECTIVES

This report reviews the emergency diagnosis and treatment of hereditary angioedema and the impact of recently introduced treatments on treatment in the United States.

DISCUSSION

Until recently, emergency physicians in the United States were hindered by the lack of rapidly effective treatment options for HAE attacks. In this article, general clinical and laboratory diagnostic procedures are reviewed against the backdrop of two case studies: one patient presenting with a known history of HAE and one with previously undiagnosed HAE. In many countries outside the United States, plasma-derived C1-INH concentrate has for decades been the first-line treatment for acute attacks. The end of 2009 ushered in a new era in the pharmacologic management of HAE attacks in the United States with the approval of two new treatment options for acute treatment: a plasma-derived C1-INH concentrate and a kallikrein inhibitor.

CONCLUSION

With access to targeted and effective treatments, emergency physicians are now better equipped for successful and rapid intervention in urgent HAE cases.

The use of penicillin skin testing to assess the prevalence of penicillin allergy in an emergency department setting

STUDY OBJECTIVE

Patient-reported penicillin allergies are often unreliable and can result in unnecessary changes in antibiotic therapy. Although penicillin allergy skin testing is commonly performed in allergy clinics, it has not been used in emergency departments (EDs) to verify self-reported allergies. We hypothesize that ED-based testing is possible and that the false-positive rate of patients with self-reported penicillin allergy are greater than 90%.

METHODS

This prospective observational cohort study enrolled a convenience sample of ED patients with a self-reported penicillin allergy. Patients were enrolled by one of 2 emergency physicians who performed skin prick and intracutaneous tests with penicillin major and minor determinants. The total testing time was 30 minutes. The proportion of false-positive self-reported allergies was computed with 95% confidence intervals (CIs) by using the score method.

RESULTS

A total of 150 patients (mean age 42 years; SD 16 years; 46% men; 47% black) were enrolled. The false-positive rate for self-reported penicillin allergy was 137 of 150 (91.3%; 95% CI 85.3% to 95.1%). There were no adverse reactions associated with penicillin skin testing. Compared with patients with a false-positive penicillin allergy result (confirmed by negative penicillin skin testing result), patients reporting a true penicillin allergy confirmed by positive penicillin skin test results tended to be more frequently men (61.5% versus 44.5%; Delta 17.0%; 95% CI -13.5% to 42%), black (69.2% versus 44.5%; Delta 24.7%; 95% CI -6.9% to 46.8%), and have no family history of drug allergy (7.7% versus 17.5%; Delta9.8%; 95% CI -20.9% to 20.4%), but self-reported other drug allergies more frequently (61.5% versus 38.7%; Delta 22.9%; 95% CI -7.7% to 47.5%).

CONCLUSION

Penicillin skin testing is feasible in the ED setting. A substantial number of patients who self-report a penicillin allergy do not exhibit immunoglobulin E-mediated sensitization to penicillin major and minor determinants. Penicillin testing in the ED may allow the use of more appropriate antibiotics for patients presenting with a history of penicillin allergy.