title: Bugged.
abstract: This was a great save. The crew could easily have missed the presentation of anaphylaxis and let the window for treatment with epinephrine slip away. This patient was in anaphylactic shock. There were no signs that supported a traumatic injury, and that, combined with diaphoresis, urticaria and tachycardic central pulse, contributed to the suspicion of anaphylaxis. Anaphylaxis is classified as distributive shock. This type of shock is caused by profound systemic vasodilation, and the heart is unable to increase output enough to maintain blood pressure. Other causes of distributive shock include sepsis and spinal cord injury. It is rare to have both hypotension and wheezing in such cases. In an anaphylactic reaction, an allergen, such as a food protein, medication, insect venom or latex, is introduced into the body. The mast cells of the immune system have a protein on their surface called IgE antibodies (Immunoglobulin E). The mast cells are filled with histamines [table: see text] and leukotrienes, which are chemical mediators. These are released when the allergen reacts with the IgE antibodies. When these mediators are released, they cause smooth-muscle constriction in the respiratory and gastrointestinal tracts, resulting in wheezing, stridor, nausea, vomiting and diarrhea. They also cause vascular dilation, leading to edema and urticaria. Most patients will present with either profound vascular effect (shock) or wheezing; this is a rather rare presentation of a patient having both. The medication best suited to counteract the effects of these medicators is epinephrine. Epinephrine is an alpha- and beta-agonist, acting to constrict the vasculature and dilate the smooth muscles in the bronchial tree. Antihistamines can alleviate symptoms of anaphylaxis, but should only be used in addition to epinephrine, not as a substitute. In life-threatening reactions, epinephrine must be given quickly and in a form that the body can distribute. Use of the subcutaneous route with a solution mixed at 1:1,000 dilution is appropriate in most patients, but if the patient is in profound shock and not perfusing the skin (pale, cold, clammy skin), then a more diluted concentration must be given i.v. at a slow rate (1 cc every minute of the 1:1,000 dilution) until the patient recovers. If i.v. access is delayed or not available, give the 1:1,000 dilution intramuscularly, in the tongue or down the endotracheal tube. Refer to your local protocols for dosage, but the usual dose of epinephrine is 0.3-0.5 mg, or 0.01 mg/kg in a child. There are more than 40 million people in the U.S. with allergic histories that place them at risk for developing anaphylaxis. Each year over 5,000 deaths are attributed to anaphylaxis. The risk of death from anaphylaxis increases with a more rapid onset of signs and symptoms. Up to 25% of patients will experience a biphasic reaction. This means there is a recurrence of symptoms several hours after the initial reaction, and it is prudent to observe patients for a period of time following their initial treatment.
authors.affiliation: Buncombe County EMS, Asheville, NC, USA. jayling@flightmedicmail.com
authors.forename: John
authors.initials: J
authors.lastname: Ayling
mesh_terms: D000328:Adult; D000707:Anaphylaxis / Q000175:diagnosis* / Q000628:therapy; D000818:Animals; D001516:Bees / Q000472:pathogenicity; D004632:Emergency Medical Services; D006801:Humans; D007299:Insect Bites and Stings / Q000175:diagnosis* / Q000503:physiopathology / Q000628:therapy; D008297:Male; D010808:Physical Examination; D014481:United States