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A Practical Guide to Anaphylaxis - Article
ABSTRACT: Anaphylaxis is a life-threatening reaction with respiratory, cardiovascular, cutaneous, or gastrointestinal manifestations resulting from exposure to an offending agent, usually a food, insect sting, medication, or physical factor. It causes approximately 1,500 deaths in the United States annually. Occasionally, anaphylaxis can be confused with septic or other forms of shock, asthma, airway foreign body, panic attack, or other entities. Urinary and serum histamine levels and plasma tryptase levels drawn after onset of symptoms may assist in diagnosis. Prompt treatment of anaphylaxis is critical, with subcutaneous or intramuscular epinephrine and intravenous fluids remaining the mainstay of management. Adjunctive measures include airway protection, antihistamines, steroids, and beta agonists. Patients taking beta blockers may require additional measures. Patients should be observed for delayed or protracted anaphylaxis and instructed on how to initiate urgent treatment for future episodes.
ABSTRACT: Drug hypersensitivity results from interactions between a pharmacologic agent and the human immune system. These types of reactions constitute only a small subset of all adverse drug reactions. Allergic reactions to medications represent a specific class of drug hypersensitivity reactions mediated by IgE. Immune-mediated drug reactions may be discussed generally in the Gell and Coombs classification system, a widely accepted conceptual framework for understanding complex immune reactions. However, some reactions involve additional, poorly understood mechanisms that are not easily classified. Identifiable risk factors for drug hypersensitivity reactions include age, female gender, concurrent illnesses, and previous hypersensitivity to related drugs. Drug hypersensitivity is a clinical diagnosis based on available data. Laboratory testing may be useful, with skin testing providing the greatest specificity. Treatment is largely supportive and includes discontinuation of the offending medication, symptomatic treatment, and patient education. Patients with penicillin allergy should avoid carbapenems, and caution should be used in prescribing cephalosporins in these patients. Reactions to radiocontrast media can be limited by pretreatment with prednisone, diphenhydramine, and either ephedrine or a histamine H2-receptor antagonist.
ABSTRACT: Otitis externa can take an acute or a chronic form, with the acute form affecting four in 1,000 persons annually and the chronic form affecting 3 to 5 percent of the population. Acute disease commonly results from bacterial (90 percent of cases) or fungal (10 percent of cases) overgrowth in an ear canal subjected to excess moisture or to local trauma. Chronic disease often is part of a more generalized dermatologic or allergic problem. Symptoms of early acute and most chronic disease include pruritus and local discomfort. If left untreated, acute disease can be followed by canal edema, discharge, and pain, and eventually by extra-canal manifestations. Topical application of an acidifying solution is usually adequate in treating early disease. An antimicrobial-containing ototopical is the preferred treatment for later-stage acute disease, and oral antibiotic therapy is reserved for advanced disease or those who are immunocompromised. Preventive measures reduce recurrences and typically involve minimizing ear canal moisture, trauma, or exposure to materials that incite local irritation or contact dermatitis.
ABSTRACT: Erythema nodosum, a painful disorder of the subcutaneous fat, is the most common type of panniculitis. Generally, it is idiopathic, although the most common identifiable cause is streptococcal pharyngitis. Erythema nodosum may be the first sign of a systemic disease such as tuberculosis, bacterial or deep fungal infection, sarcoidosis, inflammatory bowel disease, or cancer. Certain drugs, including oral contraceptives and some antibiotics, also may be etiologic. The hallmark of erythema nodosum is tender, erythematous, subcutaneous nodules that typically are located symmetrically on the anterior surface of the lower extremities. Erythema nodosum does not ulcerate and usually resolves without atrophy or scarring. Most direct and indirect evidence supports the involvement of a type IV delayed hypersensitivity response to numerous antigens. A deep incisional or excisional biopsy specimen should be obtained for adequate visualization. Erythema nodosum represents an inflammatory process involving the septa between subcutaneous fat lobules, with an absence of vasculitis and the presence of radial granulomas. Diagnostic evaluation after comprehensive history and physical examination includes complete blood count with differential; erythrocyte sedimentation rate, C-reactive protein level, or both; testing for streptococcal infection (i.e., throat culture, rapid antigen test, antistreptoly-sin-O titer, and polymerase chain reaction assay); and biopsy. Patients should be stratified by risk for tuberculosis. Further evaluation (e.g., purified protein derivative test, chest radiography, stool cultures) varies based on the individual. Erythema nodosum tends to be self-limited. Any underlying disorders should be treated and supportive care provided. Pain can be managed with nonsteroidal anti-inflammatory drugs.
ABSTRACT: Adverse reactions to contrast agents range from a mild inconvenience, such as itching associated with hives, to a life-threatening emergency. Renal toxicity is a well known adverse reaction associated with the use of intravenous contrast material. Other forms of adverse reactions include delayed allergic reactions, anaphylactic reactions, and local tissue damage. Previous allergic reactions to contrast material, asthma, and allergies are factors associated with an increased risk of developing an adverse reaction. Pretreatment of patients who have such risk factors with a corticosteroid and diphenhydramine decreases the chance of allergic reactions, including anaphylaxis, renal failure, or a possible life-threatening emergency. Awareness of the different types of risk factors and prescreening for their presence allows for early recognition and prompt treatment. Prophylactic treatment before administration of contrast material can prevent potential adverse reactions. If such reactions do occur, prompt recognition allows them to be treated immediately. Using the smallest amount of contrast material possible and low-molecular, nonionic agents also decreases the relative risk of reactions. Renal insufficiency induced by contrast material may be prevented by ensuring adequate hydration and discontinuing other nephrotoxic medications before the procedure. Low-osmolar, nonionic agents are helpful in patients with known conditions associated with adverse reactions.
ABSTRACT: Group B streptococcus is the leading cause of early-onset neonatal sepsis in the United States. Universal screening is recommended for pregnant women at 35 to 37 weeks’ gestation. The Centers for Disease Control and Prevention recently updated its guideline for the prevention of early-onset neonatal group B streptococcal disease. The new guideline contains six important changes. First, there is a recommendation to consider using sensitive nucleic acid amplification tests, rather than just routine cultures, for detection of group B streptococcus in rectal and vaginal specimens. Second, the colony count required to consider a urine specimen positive is at least 104 colony-forming units per mL. Third, the new guideline presents separate algorithms for management of preterm labor and preterm premature rupture of membranes, rather than a single algorithm for both conditions. Fourth, there are minor changes in the recommended dose of penicillin G for intrapartum chemoprophylaxis. Fifth, the guideline provides new recommendations about antibiotic regimens for women with penicillin allergy. Cefazolin is recommended for women with minor allergies. For those at serious risk of anaphylaxis, clindamycin is recommended if the organism is susceptible or if susceptibility is unknown, and vancomycin is recommended if there is clindamycin resistance. Finally, the new algorithm for secondary prevention of early-onset group B streptococcal disease in newborns should be applied to all infants, not only those at high risk of infection. The algorithm clarifies the extent of evaluation and duration of observation required for infants in different risk categories.