Allergy and Anaphylaxis, Chapter 21, Emergency Care and Transportation of the Sick and Injured: 12th edition

allergen

A substance that causes an allergic reaction.

allergic reaction

The body's exaggerated immune response to an internal or surface agent.

anaphylaxis

An extreme, life-threatening systemic allergic reaction that may include shock and respiratory failure.

angioedema

Localized areas of swelling beneath the skin, often around the eyes and lips, but can also involve other body areas as well.

envenomation

The act of injecting venom.

epinephrine

A substance produced by the body (commonly called adrenaline), and a drug produced by pharmaceutical companies that increases pulse rate and blood pressure; the drug of choice for an anaphylactic reaction.

histamines

Chemical substances released by the immune system in allergic reactions that are responsible for many of the symptoms of anaphylaxis, such as vasodilation.

immune response

The body's response to substance perceived by the body as foreign.

immune system

The body system that includes all of the structures and processes designed to mount a defense against foreign substances and disease-causing agents.

immunology

The study of the body's immune system.

leukotrienes

Chemical substances that contribute to anaphylaxis; released by the immune system in allergic reactions.

stridor

A harsh, high-pitched respiratory sound, generally heard during inspiration, that is caused by partial blockage or narrowing of the upper airway; may be audible without a stethoscope.

toxin

A harmful substance produced by living cells or organisms.

urticaria

Small areas of generalized itching and/or burning that appear as multiple raised areas on the skin; hives.

wheal

A raised, swollen, well-defined area on the skin resulting from an insect bite or allergic reaction.

wheezing

A high-pitched, whistling breath sound that is most prominent on expiration, and which suggests an obstruction or narrowing of the lower airways; occurs in asthma and bronchiolitis.

When managing allergy-related emergencies,

you must be aware of the possibility of acute airway obstruction and cardiovascular collapse and be prepared to treat these life-threatening complications.

The _______________ protects the human body from foreign substances and organisms. It protects you from bacteria, viruses and other foreign harmful substances.

Immune system

Contrary to what many people think, an allergic reaction, an exaggerated immune response to any substance, is not caused directly by an outside stimulus, such as a bite or sting or ingestion of food or medicine. Rather,

it is a reaction by the body's immune system, which releases chemicals to combat the stimulus. Among these chemicals are histamines and leukotrienes, both of which contribute to an allergic reaction.

Initially, a person becomes __________ (exposed for the first time) to the substance. When the patient is exposed to the substance again, and allergic reaction occurs.

sensitized

An allergic reaction may be

mild and local (characterized by itching, redness, or tenderness)

severe and systemic (air condition known as anaphylaxis)

The sequence of events in anaphylaxis

1) The antigen is introduced into the body

2) the antigen-antibody reaction at the surface of the mast cell

3) The release of mast cell chemical mediators

4) Specific antibody reacts with its corresponding antigen

5) chemical mediators exert their effects on end organs

During an anaphylactic reaction, chemical meditators, exert the effects on the end organs.

See: "the sequence of events in anaphylaxis," part 5. This shows you which and how the organs are affected.

Lungs: bronchospasm, vasoconstriction

Heart: decreased output, decreased coronary flow

Blood vessels: vasodilation, leakiness,

Skin: pruritus, urticaria, edema

Two of the most common signs of anaphylaxis are

Widespread urticaria (hives)

Angioedema (localized swelling)

Another observed sign is wheezing (high-pitched, whistling breath, sound heard on expiration. Wheezing usually results from bronchospasm/ bronchoconstriction, and increased mucus production.

Signs of possible upper airway narrowing include

voice changes and stridor

You may also note hypotension due to vasodilation, as well as increased capillary permeability (causing fluid from the bloodstream seep into the tissues).

The most common allergens fall into one of the following five general categories

1. Food

2. Medication

3. Plants

4. Chemicals

5. Insect bites and stings

__________ have a barbed stinger which means that they can only sting and inject venom once before they die while __________ and __________ can sting repeatedly and inject multiple rounds of venom and not die immediately.

bees

wasps and hornets orfire ants

Signs and symptoms of insect things and bites include

Sudden pain, swelling, localized heat, widespread urticaria, and redness in light-skinned people, usually at the sight of the injury.

In more severe (anaphylactic) cases, patients may experience:

Bronchospasm and wheezing

Chest tightness and coughing

Dyspnea

Anxiety

Gastrointestinal complaints

Hypotension

Occasionally, respiratory failure

If the patient is responsive, begin by obtaining the SAMPLE history (including OPQRST) and the following information specific to allergic reactions:

— Have any interventions already been completed?

— Has the patient experienced a severe allergic reaction in the past?

— Be alert for any statements regarding the ingestion of foods that commonly cause allergic reactions.

Additional signs and symptoms of an allergic reaction (respiratory system)

—Sneezing or an itchy, runny nose (early sign).

—Shortness of breath (dyspnea)

—Tightness in the chest or throat.

—Irritating, persistent dry cough.

—Hoarseness.

—Rapid, labored, or noisy respirations.

—Wheezing and/or stridor (which may progress to a silent chest with anaphylaxis; late sign).

Additional signs and symptoms of an allergic reaction (cardiovascular system)

—Increase in pulse rate (tachycardia; early sign).

—Red, flushed, hot skin (early sign) or pale, chaotic, cool skin (late sign) as the vascular system fails.

—Decrease in blood pressure (hypotension) as the blood vessels.

Additional signs and symptoms of an allergic reaction (skin)

—Flushing, itching, or burning skin, especially common over the face and upper chest.

—Urticaria over large areas of the body; may be internal or external.

—Swelling, especially of the face, neck, hands, feet, and/or tongue, either local (angioedema) or generalized.

—Cyanosis or pallor around the lips

—Warm, tingling feeling in the face, mouth, chest, feet, and hands.

Additional signs and symptoms of an allergic reaction (other findings)

—Decreasing mental status (early sign of hypoperfusion), from mild confusion or lethargy to loss of consciousness or coma.

—Anxiety; a sense of impending doom.

—Gastrointestinal problems, including nausea, vomiting, or abdominal cramps.

—Headache.

—Itchy, watery eyes.

—Dizziness.

If an allergic reaction was caused by an insect sting and the stinger is still in place,

attempt to remove the stinger by scraping the skin with the edge of a sharp, stiff object such as a credit card.

__________, which is naturally produced by the body, is a sympathomimetic hormone (mimics the sympathetic nervous system).

Epinephrine

—causes blood vessels to constrict: (reverses vasodilation and hypotension; this, in turn, elevates diastolic blood pressure and improves coronary blood flow)

—increase cardiac contractility, relieves bronchospasm in the lungs.

—acts immediately to reverse effects of anaphylaxis.

—An Auvi-Q pen is (shaped differently, injects 0.1 mg of epinephrine for patients weighing 17 to 33 lbs).

Epinephrine

(indications, contraindications, actions, side effects, typical dose)

—Indications: severe allergic reaction, causing airway, breathing, or circulatory compromise or an anaphylactic reaction

—Contraindication: none in a life-threatening emergency; however, consult medical control when the patient has a history of heart disease or acute coronary syndrome.

—Actions: vasoconstriction and increase cardiac contractility, bronchodilation.

—Side effects: tachycardia, sweating, pale, skin, dizziness, headache, palpitations.

—Typical dose:

adults = 0.3 mg (EpiPen) IM

children = 0.15 mg (EpiPen Jr) IM

Because epinephrine constricts blood vessels, it may

cause the patient's blood pressure to spike up. Other side effects include: increased pulse rate, anxiety, cardiac dysrhythmias, pallor, dizziness, chest pain, headache, nausea, and vomiting.

Note: other allergy kits may contain oral or IM antihistamines (agents that block the side effects of histamines) which work relatively slowly, within several minutes to 1 hour. Use epinephrine because its effects work within 1 minute.

An adult EpiPen is used for a patient weighing over __________ and is injected into the midanterolateral thigh.

66 lbs (30 kgs)

Note: The administration of epinephrine by IM injection uses a vial of 1:1000 concentration or (1 mg/mL).

Patients weighing less than 33 pounds will have to be dosed individually (0.01 mg/kg IM in the thigh).