19 Immunology: Anaphylactic and Anaphylactoid Reactions

Objectives Review the frequency with which immunologic emergencies occur. Understand the pathology of immunologic emergencies. Illustrate the relationship between pathology and symptomatology. Discuss treatment strategies. Discuss the objectives.

Introduction Allergic reactions may present from mild to severe. Manifestations can be related to the body system failing due to the reaction. Although an allergic reaction is designed to be beneficial to the body, when the response is severe it can be fatal. An allergic reaction may range from mild to severe. Anaphylactic and anaphylactoid reactions can rapidly cause death to the patient. The Advanced EMT's goal is to recognize the acute allergic reaction and provide appropriate care based on findings.

Epidemiology Anaphylaxis is not a reportable disease. An estimated 20,000 to 50,000 persons suffer an anaphylactic reaction each year. Anaphylaxis is not a reportable disease; therefore, the morbidity and mortality rates are not well established. Studies suggest that the lifetime risk of an individual experiencing an anaphylactic reaction is between 1 percent and 3 percent, with a mortality rate of 1 percent. It is estimated that 20,000 to 50,000 persons suffer an anaphylactic reaction in the United States each year. The incidence rate has been reported to be increasing, especially in individuals under 20 years of age. Penicillin (0.7% to 10%), insect stings (0.5% to 5%), radiocontrast media (0.22% to 1%), and food (0.0004%) remain the most common triggers. Food is the most common trigger in children, adolescents, and young adults, whereas medications, insect venom, and idiopathic (unknown) causes are more often seen in middle-aged and older individuals.

Epidemiology (cont’d) Certain drugs, medical dye, and food are the most common triggers. Food is the most common trigger in children through young adults. Insect venom and idiopathic causes are most common in middle age. Anaphylaxis is not a reportable disease; therefore, the morbidity and mortality rates are not well established. Studies suggest that the lifetime risk of an individual experiencing an anaphylactic reaction is between 1 percent and 3 percent, with a mortality rate of 1 percent. It is estimated that 20,000 to 50,000 persons suffer an anaphylactic reaction in the United States each year. The incidence rate has been reported to be increasing, especially in individuals under 20 years of age. Penicillin (0.7% to 10%), insect stings (0.5% to 5%), radiocontrast media (0.22% to 1%), and food (0.0004%) remain the most common triggers. Food is the most common trigger in children, adolescents, and young adults, whereas medications, insect venom, and idiopathic (unknown) causes are more often seen in middle-aged and older individuals.

Pathophysiology Anaphylactic reaction Patient must be sensitized Chemical mediators released with subsequent exposure Effects of mediators causes organ and system failure Characteristic presentation Review the traditional “antigen-antibody” reaction to include the process of sensitization, reexposure, chemical mediator release, and subsequent organ and system dysfunction that leads to characteristic findings.

Common Causes of Anaphylactic Reactions.

Pathophysiology (cont’d) Anaphylactoid reaction Not the typical immunologic antigen-antibody reaction Anaphylactoid trigger “directly” causes the breakdown of mast cells and basophils Chemical mediators released Characteristic presentation similar to anaphylactic reaction Review (compare and contrast) the anaphylactoid reaction with the anaphylactic reaction. The goal is to recognize the misguided immune response, rather than get worried about it being an anaphylactic or anaphylactoid reaction. Treatment between the two is the same.

Common Causes of Anaphylactoid Reactions

Pathophysiology (cont’d) Effects of chemical mediator release Increased capillary permeability Decreased vascular smooth muscle tone Increased bronchial smooth muscle tone Increased mucus secretions in the tracheobronchial tract It is probably less important that the student can name all the chemical mediators released, as compared to the actual effects of the chemical mediators on the body. This is also a good time to introduce the concept of using epinephrine to counter many of the ill effects of an acute allergic reaction.

Life-threatening responses in anaphylactic reaction: bronchoconstriction, capillary permeability, vasodilation, and an increase in mucus production. Discuss/review the progression of the reaction. Integrate symptomatology and management considerations.

Pathophysiology (cont’d) General considerations Fatal episodes related to airway occlusion, respiratory failure, severe hypoxia, and circulatory collapse The most acute cases, which can rapidly cause death, have the following features: Rapid onset Airway swelling Stridorous airway sounds Low blood pressure Bilateral wheezing

Localized angioedema to the tongue from an anaphylactic reaction Localized angioedema to the tongue from an anaphylactic reaction. (© Edward T. Dickinson, MD)

Urticaria (hives) from an allergic reaction to a penicillin-derivative drug. (© Charles Stewart, MD & Associates)

Common Signs and Symptoms of Anaphylactic Reactions Discuss presentation and how management will be aimed at limiting these effects.

Common Signs and Symptoms of Anaphylactic Reactions Discuss presentation and how management will be aimed at limiting these effects.

Common Signs and Symptoms of Anaphylactic Reactions Discuss presentation and how management will be aimed at limiting these effects.

Common Signs and Symptoms of Anaphylactic Reactions Discuss presentation and how management will be aimed at limiting these effects.

Assessment Findings Other notable assessment characteristics Parenteral injections produce the severest reactions. The faster the onset, the worse the reaction. Signs and symptoms peak in 15-30 minutes. These are not characteristics per se, but common themes in the presentation of an acute allergic reaction.

Assessment Findings (cont’d) Other notable assessment characteristics Skin and respiratory reactions are the earliest to present. Mild reactions could suddenly turn severe. Most fatalities occur within 30 minutes. The patient may have a biphasic or multiphasic reaction following treatment. These are not characteristics per se, but common themes in the presentation of an acute allergic reaction.

Differentiating Between a Mild and a Moderate to Severe Reaction. Discuss differentiation and how it pertains to management.

Assessment Findings (cont’d) Epinephrine as drug of choice Stimulation of alpha receptor sites Stimulation of beta receptor sites Ability to be given IM (by EMTs) or intravenously (by paramedics) Preferred site: IM anterior thigh Ensure that the Advanced EMT can correlate the symptoms of an acute allergic reaction with the failure of the body system causing them. Then introduce the agonistic effects of epi on alpha-1 and -2 receptors, as well as beta-1 and -2 receptors.

Emergency Medical Care Keep airway patent. Suction secretions. Administer high-flow oxygen. Ventilate the patient if needed. Administer epinephrine by auto-injector if indicated. Initiate rapid transport. Relate the management provided with the intended outcomes. Stress again the effects of epi on the pathology of the medical emergency.

Emergency Medical Care (cont’d) If an extremity is involved consider application of a loose tourniquet. Some systems allow Advanced EMTs to administer diphenhydramine (Benadryl). Treat wheezing with beta-2 agonist. Treat hypotension with IV fluid bolus. Treat hypotension secondary to beta blockers with glucagon. Relate the management provided with the intended outcomes. Stress again the effects of epi , beta-2 agonist, and glucagon on the pathology of the medical emergency. Discuss the need for IV fluid bolus and why.

Case Study You are alerted for an emergency involving a possible allergic reaction. When you arrive at the residence address, you see an adult male on the porch being propped up in a sitting position by family members on each side. His head is limply flexed forward on his chest. As you approach, you see his head bobbing with each breath, and hives covering his body. Discuss the case presentation.

Case Study (cont’d) Scene Size-Up Standard precautions taken. Scene is safe, no entry or egress problems. One patient, adult male, appears unresponsive, mid-30s. Discuss the case presentation.

Case Study (cont’d) Scene Size-Up NOI is suspected allergic reaction/dyspnea. Given the grave scene size-up, your partner radios for the ALS supervisor to also respond. Discuss the case presentation.

Case Study (cont’d) What are some concerns you have, based on the scene size-up? What are possible conditions you suspect at this time? Initial concerns are for an occluded airway. If the patient is unresponsive with their chin resting on the chest and the head bobbing with each respiration, chances are that they do not have a patent airway. Possible conditions include (in order of likelihood): Severe allergic reaction Mild allergic reaction Drug overdose Pulmonary dysfunction Cardiac dysfunction The problem with the latter three differentials is that they do not commonly present with skin findings (hives).

Case Study (cont’d) Primary Assessment Findings Patient responds to noxious stimuli with nonpurposeful motion. With each inhalation, you hear sonorous sounds and slight stridor. Breathing depth is minimal due to airway blockage, peripheral pulses are absent. Discuss as needed.

Case Study (cont’d) Primary Assessment Findings (continued) Skin is cool, pale, and diaphoretic; hives cover face, neck, chest, and arms. No indication of significant trauma. Discuss as needed.

Case Study (cont’d) Is this patient a high or low priority? Why? What are the life threats to this patient? Based on the primary survey, what emergency care would be warranted at this time? The patient is a high priority for a number of reasons: First, is the altered mental status. Second, is the partially occluded airway, and last, is the poor peripheral perfusion. Life threats include the: Maintain their own airway Ventilate effectively Produce good peripheral perfusion Immediate emergency care would be to lay the patient on their back and open the airway manually. Based on ventilatory effort, the Advanced EMT will decide if PPV is warranted. Either way, oxygen should be administered via high flow device.

Case Study (cont’d) Medical History Medications Allergies Per family, he is allergic to bee stings, but never this bad. Medications Patient has an auto-eject epi pen; no other medications. Allergies None per the patient's family. Discuss as needed.

Case Study (cont’d) Pertinent Secondary Assessment Findings Patient reportedly was outside when he walked onto the porch and said he was “stung” and then passed out. Sonorous airway sounds now absent with positioning, faint inspiratory stridor still present. Bilateral wheezing with auscultation, also poor alveolar sounds. Discuss the case presentation.

Case Study (cont’d) Pertinent Secondary Assessment Findings (continued) Peripheral pulses absent, carotid rapid and weak. Hives noted to body, skin cool and diaphoretic. Poor muscle tone bilaterally. Discuss the case presentation.

Case Study (cont’d) Pertinent Secondary Assessment Findings (continued) B/P 72/palp, heart rate 126, resps 34 and shallow. No other findings contributory to presentation. Discuss the case presentation.

Case Study (cont’d) With this information, has your field impression changed at all? What would be the next steps in management you would provide to the patient? Should the Advanced EMT still use the epi pen? Given the presentation per the family, the initial impression of an acute allergic reaction is correct, more specifically though the patient is most likely experiencing a true allergic (anaphylactic) reaction, not an anaphylactoid reaction. Next steps of management would be to: Provide PPV. Continue high-flow oxygen. Locate the patient's epi-pen for administration following medical direction approval. In terms of critical deterioration, ten minutes of additional wait time for a critical anaphylactic patient could prove fatal. If the epi-pen is available, it should be administered as soon as possible. The Advanced EMT can always administer more if needed, or use other medications geared to limit the severity of the reaction.

Case Study (cont’d) Care provided: Supine positioning, legs elevated. PPV with high-flow oxygen, NPA inserted. All tight or constrictive clothing and jewelry removed. Epi auto-eject pen administered x1 (0.3 mg). Intravenous access and administration of IV fluid. Discuss as needed.

Case Study (cont’d) In a patient with this field impression, discuss the benefits of the following interventions: Providing high-flow oxygen Positioning the patient supine Loosening tight clothing Administering epinephrine Intravenous therapy First, the use of oxygen is designed to ensure the best on loading of oxygen on the RBC is being provided. A supine position will help the Advanced EMT manage the airway, as well as help maintain perfusion to the: Heart Brain Lungs Kidneys Loosening of tight clothing will allow for edema expansion without accidently cutting off distal blood flow. The administration of epi will help reverse many of the critical findings: Stridor should be reduced (alpha effects) Blood pressure should increase (alpha effects) Breathing should become easier with a decrease in bronchoconstriction (beta-2 effects) Intravenous fluid therapy will help reverse the hypotension.

Summary An allergic reaction may range from mild to severe. Anaphylactic and anaphylactoid reactions can rapidly cause death to the patient. The Advanced EMT's goal is to recognize the acute allergic reaction and provide appropriate care based on findings. Discuss as needed.