Columns, Patient Care

Understand Allergies to Quickly Provide Treatment

Issue 6 and Volume 39.

“Ha! Sounds like food poisoning,” your partner says as you head to the ambulance to respond to a call for a patient with abdominal pain at a local restaurant.

When you arrive you’re directed to the restrooms where you find a 20-something male sitting on the floor just outside the men’s room door. He’s holding his abdomen and appears to be having slight difficulty breathing. He responds as you approach with a quick, “hello.”

He’s oriented and appears to be maintaining his airway. His skin is pink and diaphoretic. He tells you he was finishing lunch with friends when he developed what he describes as “horrible” abdominal cramping. He ran to the restroom where he experienced an episode of diarrhea. He continues to have abdominal cramping but isn’t nauseated and, when asked, states it’s slightly difficult to catch his breath.

Your exam identifies a slight increase in normal heart rate at about 110 beats per minute with a blood pressure of 128/78. His respiratory rate is 20 with a noted increased work of breathing. The pulse oximeter reads 96% with room air. Breath sounds reveal diffused wheezing. When you lift his shirt to auscultate his lung sounds you notice what appear to be hives under his armpits and in the center of his chest. Your food poisoning call is now looking more like an allergic reaction.

The patient denies having food allergies and any significant medical history, saying he only suffers from seasonal allergies that he controls with over-the-counter medications. He says he’s eaten the same meal he ate today other times without issue.

Reevaluation of vital signs and the physical exam reveals no changes. The patient is placed on oxygen, which relieves his dyspnea. The patient denies the feeling of swelling in his throat or tongue.

Your partner establishes an IV of normal saline and you begin transport, keeping a close watch on the patient’s breathing, airway and blood pressure. Patient care is transferred to the ED staff without change. The patient was given oral Benadryl (diphenhydramine) in the ED, monitored for a couple of hours and sent home.

Allergies are a response of the immune system, which is designed to protect us from foreign invaders and keep us healthy. When we’re exposed to a pathogen the body feels is harmful, an immune response is launched.

The first response is nonspecific or innate immunity, where neutrophils (white blood cells) and macrophages (derived from monocytes, another white blood cell) begin a process of phagocytosis. These cells devour and eliminate pathogens.

The secondary response is acquired immunity. Once a person has been exposed to a foreign invader or antigen, the body has the ability to make cells specific to the antigen known as antibodies. Then, when the body is exposed to that same antigen again, the body swiftly eliminates it—in many cases without us knowing we were exposed.

Each time the body is exposed to the same antigen, more antibodies are produced and the body’s reaction is swifter. In a normal response to an antigen, the body works to contain the antigen and increase the flow of white blood cells to the area through local vasodilation.

When a person develops an allergy, the body has identified what for most people is a normal substance as being a harmful foreign invader and creates antibodies to fight it. In some allergic reactions the response may be localized—in other words, touching something someone is allergic to may result in local hives.

It’s possible for a person to have an allergic reaction with no previously recognized signs and symptoms, as is the case with the patient described here. Common symptoms include shortness of breath secondary to bronchial constriction and upper airway swelling, dizziness secondary to a drop in blood pressure, hives and itching, and gastrointestinal complaints such as nausea, cramping, vomiting and diarrhea. Patients may experience shortness of breath before providers hear wheezing, and patients will describe a swelling in their mouth and throat before it becomes obvious to providers.

Hives may not be openly obvious, presenting on the chest and axilla prior to other areas. Benadryl (diphenhydramine) can help by blocking the histamine response, which is responsible for many of the symptoms seen with allergic reactions.

In severe cases of allergic reactions with multiple organ involvement (called anaphylaxis), symptoms can progress swiftly into anaphylactic shock, closing the airway and dropping blood pressure critically low.

Advanced airway placement, IV fluid resuscitation and medications to increase blood pressure may be necessary. These patients need epinephrine immediately. Epinephrine is beneficial treating the life-threatening effects of anaphylaxis by dilating the airways or bronchials, helping patients breathe better, and causing the blood vessels to constrict, helping to increase blood pressure.

Early recognition of an allergic reaction is crucial and providers must watch the patient’s breathing and blood pressure closely. Although this patient exhibited classic signs of an allergic reaction, initial symptoms may not be the typical shortness of breath and hives as described in many textbooks. Providers should also remember that stable patients can become unstable quickly and should be monitored closely.

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