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Anaphylactic shock
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Anaphylactic shock

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  • 1. [Type text] Anaphylactic shock is a severe, potentially life-threatening allergic reaction. It can occur within seconds or minutes of exposure to something person is allergic to, such as the venom from a bee sting or a peanut. The flood of chemicals released by immune system during anaphylaxis can cause person to go into shock; blood pressure drops suddenly and airways narrow, blocking normal breathing. Signs and symptoms of anaphylaxis include a rapid, weak pulse, skin rash, and nausea and vomiting. Common triggers of anaphylaxis include certain foods, some medications, insect venom and latex. Anaphylaxis requires an immediate trip to the emergency room and an injection of epinephrine. If anaphylaxis isn't treated right away, it can lead to unconsciousness or even death. Pathophysiology Rapid onset of increased secretion from mucous membranes, increased bronchial smooth muscle tone, decreased vascular smooth muscle tone, and increased capillary permeability occur after exposure to an inciting substance. These effects are produced by the release of mediators, which include histamine, leukotriene C4, prostaglandin D2, and tryptase. In the classic form, mediator release occurs when the antigen (allergen) binds to antigen-specific immunoglobulin E (IgE) attached to previously sensitized basophils and mast cells. The mediators are released almost immediately when the antigen binds. In an anaphylactoid reaction, exposure to an inciting substance causes direct release of mediators, a process that is not mediated by IgE. Increased mucous secretion and increased bronchial smooth muscle tone, as well as airway edema, contribute to the respiratory
  • 2. [Type text] symptoms observed in anaphylaxis. Cardiovascular effects result from decreased vascular tone and capillary leakage. Histamine release in skin causes urticarial skin lesions. The most common inciting agents in anaphylaxis are parenteral antibiotics (especially penicillins), IV contrast materials, Hymenoptera stings, and certain foods (most notably, peanuts). Oral medications and many other types of exposures also have been implicated. Anaphylaxis also may be idiopathic. Causes Common anaphylaxis triggers include: - Certain medications, especially penicillin - Foods such as peanuts, tree nuts (walnuts, pecans), fish, shellfish, milk and eggs - Insect stings from bees, yellow jackets, wasps, hornets and fire ants Less common causes of anaphylaxis include: - Latex - Muscle relaxants used in general anesthesia - Exercise Anaphylaxis triggered by exercise varies from person to person. In some people, aerobic activity such as jogging triggers anaphylaxis. In others, less intense physical activity such as yard work can trigger a reaction. Eating certain foods before exercise or exercising when the weather is hot, cold or humid has also been linked to anaphylaxis in some people.
  • 3. [Type text] Anaphylaxis symptoms are sometimes caused by aspirin, other nonsteroidal anti-inflammatory drugs — such as ibuprofen (Advil, Motrin, others) and naproxen (Aleve, Midol Extended Relief) — and the intravenous (IV) contrast used in some X-ray imaging tests. Although similar to allergy-induced anaphylaxis, this type of reaction isn't triggered by allergy antibodies. In some cases, the cause of anaphylaxis is never identified. This is known as idiopathic anaphylaxis Symptoms- Anaphylactic reactions almost always involve the skin or mucous membranes, most of the patients have some combination of urticaria, erythema, pruritus, or angioedema. The classic skin manifestation is urticaria. - The upper respiratory tract commonly is involved, with complaints of nasal congestion, sneezing, or coryza. Cough, hoarseness, or a sensation of tightness in the throat may presage significant airway obstruction. - Eyes may itch and tearing may be noted. Conjunctival injection may occur - Dyspnea is present when patients have bronchospasm or upper airway edema. Hypoxia and hypotension may cause weakness, dizziness, or syncope. Chest pain may occur due to bronchospasm or myocardial ischemia (secondary to hypotension and hypoxia). - GI symptoms of cramp like abdominal pain with nausea, vomiting, or diarrhea also occur but are less common, except in the case of food allergy.
  • 4. [Type text] Signs - Abormal heart rhythm (arrhythmia) - Fluid in the lungs (pulmonary edema) - Hives - Low blood pressure - Mental confusion - Rapid pulse - Skin that is blue from lack of oxygen or pale from shock - Swelling (angioedema) in the throat that may be severe enough to block the airway - Swelling of the eyes or face - Wheezing Diagnosis- diagnosis is mainly based on clinics & medical history like exposure to allergens Laboratory Studies- The diagnosis of anaphylaxis is clinical and does not rely on laboratory testing. - The only potentially useful test at the time of reaction is measurement of serum mast cell tryptase, though the test's availability and slow turn around time greatly limit its clinical utility. Tryptase is released from mast cells in both anaphylactic and anaphylactoid reactions. Levels are usually raised in severe reactions. Sensitivity testing- Testing for sensitivity to penicillin antibiotics may be useful when a penicillin or cephalosporin antibiotic is the
  • 5. [Type text] drug of choice for a serious infection in a patient who has a history of severe allergic reaction. Specific IgE tests may be preferable to skin prick tests when investigating patients with a history of anaphylaxis Treatment- What to do in an emergency - If someone who is having an allergic reaction and shows signs of shock caused by anaphylaxis, a quick reaction is essential. Signs and symptoms of shock caused by anaphylaxis include pale, cool and clammy skin, weak and rapid pulse, trouble breathing, confusion and loss of consciousness, take the following steps immediately: - Call 911 or emergency medical help. - Check the person's pulse and breathing and, if necessary, administer CPR or other first aid measures. - If the person has medications to treat an allergy attack, such as an epinephrine auto-injector or antihistamines, give them right away. Parenteral adrenergic agents- Reverse cardiovascular, cutaneous, GI, and pulmonary manifestations of anaphylaxis. Epinephrine- 0.3-1.0 ml 1:1000 solution IM, repeated at 5-10 mins if initial response is inadequate Inhaled beta-agonists- Used to treat bronchospasm. Doses are identical to those used in the treatment of asthma. Albuterol- Numerous inhaled beta-agonists are used for treatment of bronchospasm; albuterol is the most commonly used preparation. 0.5 mL 0.5% soln in 2.5 cc NS nebulized q15min
  • 6. [Type text] Antihistamines- Diphenhydramine(Benadryl)- 25-50 mg IV/IM q46h , 50 mg PO q4-6h Corticosteroids- Methylprednisolone- 40-250 mg IV/IM q6h, 60 mg PO qd 2- Antidote, Hypoglycemia- inotropic, chronotropic, and vasoactive effects, useful in patient who are resistant to epinephrine or other adrenergic agents. 1-10 mg IV/IM/SC; typically 1-2 mg q5min to effect
  • 7. [Type text] Antihistamines- Diphenhydramine(Benadryl)- 25-50 mg IV/IM q46h , 50 mg PO q4-6h Corticosteroids- Methylprednisolone- 40-250 mg IV/IM q6h, 60 mg PO qd 2- Antidote, Hypoglycemia- inotropic, chronotropic, and vasoactive effects, useful in patient who are resistant to epinephrine or other adrenergic agents. 1-10 mg IV/IM/SC; typically 1-2 mg q5min to effect