Objectives Define Hypersensitivity Reaction. Mention the Types of Hypersensitivity Reactions. Define Anaphylaxis. Mention the Etiologic Causes. Explain the Pathophysiologic Mechanism. Mention the Signs & Symptoms. Demonstrate the Diagnostic Investigations. Display the Treatment & First Aid.
Hypersensitivity Reaction Injurious, or pathologic, immune reactions are called hypersensitivity reactions. Hypersensitivity reactions may occur in two situations. First, responses to foreign antigens may be dysregulated or uncontrolled, resulting in tissue injury. Second, the immune responses may be directed against self antigens, as a result of the failure of self-tolerance (autoimmunity).
Types of hyper sensitivity reactions Immediate Antibody- immune complex T cell-mediatedhypersensitivity mediated diseases diseases Mast cell Antibodies Antibody- Reactions release directed antigen of T histamine against cell or complex lymphocytes and other tissue deposit in mediators antigens blood vessels
Anaphylaxis Ana (without), phylaxis (protection). Acute multi-systemic allergic reaction involving the skin, airway, vascular system, and GI. Sever immediate (type I) hypersensitivity reaction. True & pseudo-anaphylaxis.
EtiologyCauses of anaphylaxis in a study of 266 patients (Data from Kemp et al) 2% Food 7% Idiopathic 20% 34% Drugs Exercise 37% Latex, hormons, ins ect bites
Signs & SymptomsEyes Itching tearing swelling around the redness eyes
Signs & SymptomsNose &mouth Sneezing runny nose nasal congestion swelling of the metallic taste tongue
Signs & SymptomsLungs andthroat wheezing or other Difficulty breathing coughing chest tightness sounds increased mucus throat swelling or or a sensation of change in voice production itching choking
Signs & SymptomsHeart and circulation Dizziness weakness fainting rapid, slow, or low blood pressure irregular heart rate
Signs & SymptomsDigestive system Nausea vomiting cramps diarrhea
Signs & symptomsNervous system Anxiety confusion sense of impending doom
Diagnosis The diagnosis of anaphylaxis is based upon symptoms that occur suddenly after being exposed to a potential trigger. Differential diagnosis severe asthma attack heart attack panic attack food poisoning An increased amount of tryptase protein can be measured in a blood sample collected during the first three hours after anaphylaxis symptoms have begun. tryptase levels are seldom elevated in food-induced
First Aid Place patient in Establish and Trendelenburg maintain airway. position. Give oxygen via Place a tourniquet nasal cannula as above the reaction needed. site. Epinephrine at the site of antigen Start IV to rise BP. injection.
Treatment EPINEPHRINE Benadryl (diphenhydramine) - H1 antagonist Tagamet (cimetidine) - H2 antagonist Corticosteroid therapy In severe anaphylaxis, observe for 6 hours or longer
Prevention Avoid the responsible allergen (e.g. food, drug, latex, etc.). Keep an adrenaline kit (e.g. Epipen) and Benadryl on hand at all times. Wear medic Alert bracelets .Venom immunotherapy is highly effective in protecting insect-allergic individuals.