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58 ANAPHYLACTIC SHOCK PEER REVIEWED Clinical signs sometimes subside and acutely reappear after several hours. These are known as biphasic reactions and can increase mortality if they are not recognized and treated appropriately. 18 Obtaining a detailed history about past allergic reactions, vaccinations, outside exposure, and previous medical ailments can be an important tool in diagnosing anaphylaxis. TREATMENT Treatment of anaphylaxis is entirely based on clinical signs but should follow the guidelines for fundamental life support. Treatment should be initiated quickly and take priority over diagnostics because of the likelihood of rapid progression of clinical signs and increasing possibility of death. 14,16 As with all life support treatment, rapid triage assessment, including airway, breathing, circulation, and mental status, is paramount. Delays in treatment can lead to worsening outcomes. 2 Immunologic and nonimmunologic hypersensitivity responses produce identical clinical signs and are thus treated the same. 1,2 Airway If the patient presents in respiratory distress, it may be necessary to secure an airway. An endotracheal tube may be placed for patients with laryngeal swelling. If an endotracheal tube is not feasible because of swelling, a temporary tracheostomy tube may be placed surgically. Albuterol (a β-agonist) may help cause bronchodilation and decrease bronchospasm. Pharmacologic Doses for all drugs discussed below are listed in Box 2 . Epinephrine As an α- and β-agonist, epinephrine is essential in the treatment of anaphylaxis. It has the following effects: • α-adrenergic effects. Vasoconstriction, which increases vascular resistance and thus blood pressure and coronary perfusion, and decreased edema, which leads to relief of upper airway obstruction • β 1 -adrenergic effects. Positive inotropic and chronotropic activity, leading to increased cardiac output • β 2 -adrenergic effects. Bronchodilation, leading to increased tissue oxygenation; also, the rate of adenosine triphosphate hydrolysis into adenosine monophosphate increases, which results in inhibition of histamine and cytokine release from mast cells and basophils, truncating the type 1 hypersensitivity reaction In total, epinephrine works to accelerate heart rate, increase cardiac contractions, decrease mast cell degranulation, and improve oxygenation through bronchodilation. 19 Potential adverse reactions include ventricular arrhythmias; hypertension; tachycardia; and transient, mild effects, including pallor, tremors, and dizziness (in humans). 2 Epinephrine may be administered via the endotracheal tube; via SC, IM, or IV routes; or as a continuous-rate infusion (CRI). Current recommendations state that an initial dose BOX 2. Drugs Used in the Treatment of Anaphylaxis Epinephrine 19 • 0.02–0.04 mg/kg via endotracheal tube • 0.2–0.5 mg (total dose) SC or IM • 0.01–0.1 mg/kg IV • 0.05 mcg/kg/min CRI Antihistamines 20 • Famotidine: 0.5–1 mg/kg IV • Ranitidine: 0.5–2.5 mg/kg IV • Diphenhydramine: 1–4 mg/kg IM (dogs); 0.5 to 2 mg/kg IM (cats) Glucocorticoids 21 • Dexamethasone-SP: 0.1–0.5 mg/kg IV • Prednisone: 0.5–1.0 mg/kg PO Bronchodilators 16 • Albuterol: 1 to 2 puffs via inhaler; can be administered up to every 15 minutes as a 90-g/puff inhaler, up to 3 doses 10 • Aminophylline: 5–10 mg/kg IM or slow IV Vasopressors 16 • Norepinephrine: 0.01–1 mcg/kg/min IV CRI • Dopamine: 5–10 mcg/kg/min IV CRI • Vasopressin: 0.5–1.25 mU/kg/min IV CRI Anticholinergic 16 • Atropine: 0.02–0.04 mg/kg IV