Drug used in anaphylaxis: September 2011

Ans. B: Epinephrine Adrenaline 1:1000 solution intramuscularly produces a dramatic reversal of the hypotension, bronchospasm and laryngeal edema and is life saving. Anaphylaxis It is defined as "a serious allergic reaction that is rapid in onset and may cause death". It can result in a number of symptoms including throat swelling, an itchy rash, and low blood pressure. On a pathophysiologic level it is an acute multi-system type I hypersensitivity reaction. "True" anaphylaxis is caused by degranulation of mast cells or basophils mediated by immunoglobulin E (IgE), and pseudo-anaphylaxis occurs without IgE mediation The most common areas affected include: skin (80% to 90%), respiratory (70%), gastrointestinal (30% to 45%), hea and vasculature (10% to 45%), and central nervous system (10% to 15%) Skin involvement may include generalized hives, itchiness, flushing, and swelling of the lips, tongue, or throat. Respiratory symptoms may include shoness of breath, wheezes or stridor, and low oxygen. Gastrointestinal symptoms may include crampy abdominal pain, diarrhea, and vomiting. Anaphylaxis can occur in response to any allergen. Common triggers include insect bites or stings, foods, medication, and latex rubber. Foods are the most common trigger in children and young adults while medications and insect bites and stings are more common in older adults. Biphasic anaphylaxis is the recurrence of symptoms within 1-72 hours with no fuher exposure to the allergen. Anaphylactic shock is anaphylaxis associated with systemic vasodilation that results in low blood pressure. It is also associated with severe bronchoconstriction to the point where the individual is unable to breathe. Pseudoanaphylaxis has a similar presentation and treatment to that of anaphylaxis, however, it does not involve an allergic reaction but is due to direct mast cell degranulation. This can result from morphine, radiocontrast, aspirin and muscle relaxants. Epinephrine (adrenaline) is the primary treatment for anaphylaxis with no absolute contraindication to its use. It is recommended that it be given intramuscularly into the mid anterolaterial thigh as soon as the diagnosis is suspected. Minor adverse effects from epinephrine include tremors, anxiety, headaches, and palpitations.