Anaphylactic shock is an acute pathological condition that occurs when an allergen re-penetrates, resulting in severe hemodynamic disorders and hypoxia. The main causes of anaphylaxis are the ingestion of various medications and vaccines, insect bites, and food allergies. With a severe degree of shock, loss of consciousness quickly occurs, a coma develops and, in the absence of emergency care, a fatal outcome. Treatment consists in stopping the allergen from entering the body, restoring the function of blood circulation and respiration, and, if necessary, resuscitation measures.
Anaphylactic shock (anaphylaxis) is a severe systemic allergic reaction of an immediate type that develops upon contact with foreign substances-antigens (medications, serums, radiopaque drugs, food, snake and insect bites), which is accompanied by severe circulatory disorders and organ and system functions.
Anaphylactic shock develops in about one in 50 thousand people, and the number of cases of this systemic allergic reaction is growing every year. So, in the United States of America, more than 80 thousand cases of anaphylactic reactions are registered every year, and the risk of at least one episode of anaphylaxis during life exists in 20-40 million US residents. According to statistics, in about 20% of cases, the cause of anaphylactic shock is the use of medications. Anaphylaxis is often fatal.
Any substance entering the human body can become an allergen leading to the development of an anaphylactic reaction. Anaphylactic reactions are more likely to develop in the presence of a hereditary predisposition (there is an increase in the reactivity of the immune system – both cellular and humoral). The most common cause of anaphylactic shock are:
- Introduction of medications. These are antibacterial (antibiotics and sulfonamides), hormonal agents (insulin, adrenocorticotropic hormone, corticotropin and progesterone), enzyme preparations, anesthetics, heterologous serums and vaccines. Hyperreaction of the immune system can also develop on the introduction of radiopaque drugs used in instrumental studies.
- Bites and stings. Another causal factor of anaphylactic shock is the bites of snakes and insects (bees, bumblebees, hornets, ants). In 20-40% of cases of bee stings, beekeepers become victims of anaphylaxis.
- Food allergy. Anaphylaxis often develops on food allergens (eggs, dairy products, fish and seafood, soy and peanuts, food additives, dyes and flavors, as well as biological products used for processing fruits and vegetables). So, in the USA, more than 90% of cases of severe anaphylactic reactions develop on hazelnuts. In recent years, the number of cases of anaphylactic shock to sulfites – food additives used for longer preservation of the product – has increased. These substances are added to beer and wine, fresh vegetables, fruits, sauces.
- Physical factors. The disease can develop under the influence of various physical factors (work related to muscle tension, sports training, cold and heat), as well as when taking certain foods (more often shrimp, nuts, chicken meat, celery, white bread) and subsequent physical activity (work in the backyard, sports, running, swimming, etc.)
- Allergy to latex. Cases of anaphylaxis on latex products (rubber gloves, catheters, tire products, etc.) are becoming more frequent, and cross-allergy to latex and some fruits (avocados, bananas, kiwis) is often observed.
Anaphylactic shock is an immediate generalized allergic reaction, which is caused by the interaction of a substance with antigenic properties and immunoglobulin IgE. Upon repeated admission of the allergen, various mediators are released (histamine, prostaglandins, chemotactic factors, leukotrienes, etc.) and numerous systemic manifestations develop from the cardiovascular, respiratory systems, gastrointestinal tract, skin.
These are vascular collapse, hypovolemia, contraction of smooth muscles, bronchospasm, hypersecretion of mucus, edema of various localization and other pathological changes. As a result, the volume of circulating blood decreases, blood pressure decreases, the vasomotor center is paralyzed, the shock volume of the heart decreases and the phenomena of cardiovascular insufficiency develop. Systemic allergic reaction in anaphylactic shock is accompanied by the development of respiratory failure due to bronchial spasm, accumulation of viscous mucous discharge in the bronchial lumen, the appearance of hemorrhages and atelectasis in lung tissue, stagnation of blood in the small circulatory circle. Violations are also noted from the skin, abdominal and pelvic organs, the endocrine system, and the brain.
Symptoms of anaphylactic shock
Clinical symptoms of anaphylactic shock depend on the individual characteristics of the patient’s body (sensitivity of the immune system to a specific allergen, age, presence of concomitant diseases, etc.), the method of penetration of a substance with antigenic properties (parenterally, through the respiratory tract or digestive tract), the predominant “shock organ” (heart and blood vessels, respiratory tract, skin). At the same time, the characteristic symptoms can develop both at lightning speed (during parenteral administration of the drug) and 2-4 hours after meeting with the allergen.
Acute disorders of the cardiovascular system are characteristic of anaphylaxis: decrease in blood pressure with the appearance of dizziness, weakness, fainting, arrhythmia (tachycardia, extrasystole, atrial fibrillation, etc.), the development of vascular collapse, myocardial infarction (pain behind the sternum, fear of death, hypotension). Respiratory signs of anaphylactic shock are the appearance of pronounced shortness of breath, rhinorrhea, dysphonia, wheezing, bronchospasm and asphyxia. Neuropsychic disorders are characterized by severe headache, psychomotor agitation, a sense of fear, anxiety, convulsive syndrome. Pelvic organ dysfunction (involuntary urination and defecation) may occur. Skin signs of anaphylaxis – the appearance of erythema, urticaria, angioedema.
The clinical picture will differ depending on the severity of anaphylaxis. There are 4 degrees of severity:
- With the first degree of shock, the violations are minor, blood pressure (BP) is reduced by 20-40 mm Hg. Consciousness is not disturbed, dry throat, cough, chest pain, feeling of heat, general anxiety, there may be a rash on the skin.
- For the II degree of anaphylactic shock, more pronounced disorders are characteristic. At the same time, systolic blood pressure drops to 60-80, and diastolic blood pressure drops to 40 mm Hg. Worries about a feeling of fear, general weakness, dizziness, rhinoconjunctivitis, skin rashes with itching, Quincke’s edema, difficulty swallowing and talking, abdominal and lower back pain, heaviness behind the sternum, shortness of breath at rest. Repeated vomiting often appears, the control of the process of urination and defecation is disrupted.
- The III degree of severity of shock is manifested by a decrease in systolic blood pressure to 40-60 mm Hg, and diastolic – to 0. Loss of consciousness occurs, the pupils dilate, the skin is cold, sticky, the pulse becomes threadlike, convulsive syndrome develops.
- The IV degree of anaphylaxis develops at lightning speed. At the same time, the patient is unconscious, blood pressure and pulse are not determined, there is no cardiac activity and breathing. Urgent resuscitation measures are needed to save the patient’s life.
Upon exiting the shock state, the patient retains weakness, lethargy, lethargy, fever, myalgia, arthralgia, shortness of breath, heart pain. Nausea, vomiting, and abdominal pain may occur. After the relief of acute manifestations of anaphylactic shock (in the first 2-4 weeks), complications often develop in the form of bronchial asthma and recurrent urticaria, allergic myocarditis, hepatitis, glomerulonephritis, systemic lupus erythematosus, nodular periarteritis, etc.
The diagnosis of anaphylactic shock is established mainly by clinical symptoms, since there is no time for detailed collection of anamnestic data, laboratory tests and allergological samples. Only taking into account the circumstances during which anaphylaxis occurred can help – parenteral administration of a drug, snake bite, eating a certain product, etc.
During the examination, the general condition of the patient, the function of the main organs and systems (cardiovascular, respiratory, nervous and endocrine) is assessed. Already a visual examination of a patient with anaphylactic shock allows you to determine the clarity of consciousness, the presence of a pupillary reflex, the depth and frequency of breathing, the condition of the skin, maintaining control over the function of urination and defecation, the presence or absence of vomiting, convulsive syndrome. Next, the presence and qualitative characteristics of the pulse in the peripheral and main arteries, the level of blood pressure, auscultative data when listening to the tones of the heart and breathing over the lungs are determined.
After providing emergency care to a patient with anaphylactic shock and eliminating an immediate threat to life, laboratory and instrumental studies are carried out to clarify the diagnosis and exclude other diseases with similar symptoms:
- Laboratory tests. During a laboratory general clinical examination, a clinical blood test is performed (leukocytosis, an increase in the number of erythrocytes, neutrophils, eosinophils are more often detected), the severity of respiratory and metabolic acidosis is assessed (pH, partial pressure of carbon dioxide and oxygen in the blood is measured), the water-electrolyte balance, indicators of the blood coagulation system, etc. are determined.
- Allergological examination. In anaphylactic shock, it provides for the determination of tryptase and IL-5, the level of general and specific immunoglobulin E, histamine, and after the relief of acute manifestations of anaphylaxis, the detection of allergens using skin samples and laboratory testing.
- Instrumental diagnostics. The electrocardiogram shows signs of overload of the right heart, myocardial ischemia, tachycardia, arrhythmia. A chest X-ray may show signs of emphysema of the lungs. During the acute period of anaphylactic shock and for 7-10 days, blood pressure, heart rate and respiration, ECG are monitored. If necessary, pulse oximetry, capnometry and capnography are prescribed, arterial and central venous pressure is determined by an invasive method.
Differential diagnosis is carried out with other conditions that are accompanied by a marked decrease in blood pressure, impaired consciousness, breathing and cardiac activity: cardiogenic and septic shock, myocardial infarction and acute cardiovascular insufficiency of various genesis, pulmonary embolism, syncopal conditions and epileptic syndrome, hypoglycemia, acute poisoning, etc. Anaphylactic shock should be distinguished from similar anaphylactoid reactions that develop already at the first meeting with an allergen and in which immune mechanisms (antigen-antibody interaction) are not involved.
Sometimes differential diagnosis with other diseases is difficult, especially in situations where there are several causal factors that caused the development of shock (a combination of different types of shock and the addition of anaphylaxis in response to the introduction of any medication).
Treatment of anaphylactic shock
Therapeutic measures for anaphylactic shock are aimed at the speedy elimination of violations of the function of vital organs and body systems. First of all, it is necessary to eliminate contact with the allergen (stop the introduction of a vaccine, drug or radiopaque substance, remove the sting of a wasp, etc.), if necessary, limit venous outflow by applying a tourniquet to the limb above the site of drug administration or insect sting, as well as prick this place with a solution of adrenaline and apply cold. It is necessary to restore the patency of the respiratory tract (duct insertion, urgent tracheal intubation or tracheotomy), to ensure the supply of pure oxygen to the lungs.
The administration of sympathomimetics (adrenaline) is carried out subcutaneously repeatedly, followed by intravenous drip administration until the condition improves. In severe anaphylactic shock, dopamine is injected intravenously in an individually selected dose. Glucocorticoids (prednisone, dexamethasone, betamethasone) are included in the emergency care scheme, infusion therapy is performed to replenish the volume of circulating blood, eliminate hemoconcentration and restore an acceptable level of blood pressure. Symptomatic treatment includes the use of antihistamines, bronchodilators, diuretics (according to strict indications and after stabilization of blood pressure).
Inpatient treatment of patients with anaphylactic shock is carried out for 7-10 days. In the future, monitoring is necessary to identify possible complications (late allergic reactions, myocarditis, glomerulonephritis, etc.) and their timely treatment.
Prognosis and prevention
The prognosis for anaphylactic shock depends on the timeliness of adequate therapeutic measures and the general condition of the patient, the presence of concomitant diseases. Patients who have suffered an episode of anaphylaxis should be registered with a local allergist. They should be issued an allergological passport with notes on the factors causing the phenomena of anaphylactic shock. To prevent such a condition, contact with such substances should be excluded.