Management of Acute Hypersensitivity Reactions

Friday, September 26, 2008

Management of Acute Hypersensitivity Reactions

Type I Hypersensitivity reactions are immunologic responses to a foreign antigen to which a patient has been previously sensitized (immediate hypersensitivity or anaphylaxis). Anaphylactoid reactions are not immunologically mediated; however, symptoms and treatment are similar.

Process of Acute Hypersensitivity Reactions

Signs and symptoms of Acute Hypersensitivity Reactions :

Acute hypersensitivity reactions typically begin within 1 to 30 minutes of exposure to the offending antigen. Tingling sensations and a generalized flush may proceed to a fullness in the throat, chest tightness, or a “feeling of impending doom.” Urticaria and sweating are most common sign and symtomp of acute hypersensitivity reactions. Severe reactions include life-threatening involvement of the airway and cardiovascular system.

Acute Hypersensitivity Reactions: Urticaria

Acute Hypersensitivity Reactions: Allergic area

Treatment of Acute Hypersensitivity Reactions :

When this case is happened , an appropriate and immediate treatment is imperative. The following general measures are commonly employed to the patient who has acute hypersensitivity reactions :

• Administered of Epinephrine.
  Epinephrine Sub Cutaneouse (SC) Injection : 1:1000, 0.2 to 0.5 mg (0.2 to 0.5 ml) is primary treatment. In children, administer 0.01 mg/kg or 0.1 mg. Doses may be repeated every 5 to 15 minutes if needed. A succession of small doses is more effective and less dangerous than a single large dose. Additionally, 0.1 mg may be introduced into an injection site where the offending drug was administered. If appropriate, the use of a tourniquet above the site of injection of the causative agent may slow its absorption and distribution. However, remove or loosen the tourniquet every 10 to 15 minutes to maintain circulation.
  
  Epinephrine Intravenouse (IV) Injection as general indicated in the presence of hypotension is often recommended in a 1:10,000 dilution, 0.3 to 0.5 mg over 5 minutes; repeat every 15 minutes, if necessary. In children, inject 0.1 to 0.2 mg or 0.01 mg/kg/dose over 5 minutes; repeat every 30 minutes.
  
  A conservative IV epinephrine protocol includes 0.1 mg of a 1:100,000 dilution (0.1 mg of a 1:1000 dilution mixed in 10 ml normal saline) given over 5 to 10 minutes. If an IV infusion is necessary, administer at a rate of 1 to 4 mcg/min. In children, infuse 0.1 to 1.5 (maximum) mcg/kg/min.
  
  Giving epinephrine 1:10,000 through an endotracheal tube is a possible way, if no other parenteral access is available, directly into the bronchial tree. It is rapidly absorbed there from the capillary bed of the lung.


• Check for Airway.
  Ensure a patent airway via endotracheal intubation or cricothyrotomy (ie, inferior laryngotomy, used prior to tracheotomy) and administer oxygen. Severe respiratory difficulty may respond to IV aminophylline or to other bronchodilators.


• Check for Blood Pressure.
  Hypotension in acute hypersensitivity reactions is should be recumbent with feet elevated. Depending upon the severity, consider the following measures :
  
  - Establish a patent IV catheter in a suitable vein.
  - Administer IV fluids (eg, Normal Saline, Lactated Ringer's).
  - Administer plasma expanders.
  - Administer cardioactive agents (see group and individual monographs). Commonly recommended agents include dopamine, dobutamine, norepinephrine, and phenylephrine.


• Adjunctive therapy.
  Adjunctive therapy does not alter acute reactions, but may modify an ongoing or slow-onset process and shorten the course of the reaction.
  
  - Antihistamines : Diphenhydramine 50 to 100 mg IM or IV, continued orally at 5 mg/kg/day or 50 mg every 6 hours for 1 to 2 days. For children, give 5 mg/kg/day, maximum 300 mg/day. Chlorpheniramine Adults, 10 to 20 mg; children, 5 to 10 mg IM or slowly IV. Hydroxyzine 10 to 25 mg orally or 25 to 50 mg IM 3 to 4 times daily.
  
  - Corticosteroids : Eg, hydrocortisone IV 100 to 1000 mg or equivalent, followed by 7 mg/kg/day IV or oral for 1 to 2 days. The role of corticosteroids is controversial.
  
  - H2 antagonists : Cimetidine Children, 25 to 30 mg/kg/day IV in 6 divided doses; Adults, 300 mg every 6 hours. Ranitidine 50 mg IV over 3 to 5 minutes. May be of value in addition to H1 antihistamines, although this opinion is not universally shared.