Anaphylaxis is a severe allergic reaction that occurs after exposure to specific allergens.
Anaphylaxis is a severe systemic allergic reaction resulting in shock after exposure to specific allergens. It is mainly characterized by skin flushing, itching, chest tightness, shortness of breath, palpitations, low blood pressure, confusion, etc. It is caused by exposure to heterogeneous proteins, medications, polysaccharides, transfusion of blood products, etc. It is necessary to remove the allergens immediately, and to use epinephrine, antihistamines and glucocorticosteroids to provide emergency treatment.
Definition
Anaphylaxis is a severe, fatal systemic reaction characterized by acute peripheral insufficiency of perfusion after exposure to specific allergens (allergens).
Anaphylaxis usually develops suddenly within minutes to hours of exposure to the allergen and first aid must be given to save the patient’s life.
Classification
Classification according to the time of onset
Acute: Anaphylaxis that develops immediately or within 5 minutes after exposure to a specific allergen.
Delayed type: refers to anaphylaxis that develops more than 5 minutes after exposure to specific allergens [1].
Morbidity.
Most of the disease is drug induced. Statistically, 90% of them are due to penicillin [2].
Anaphylaxis has a high mortality rate, which can be as high as 15.4% to 28% [3].
Etiology
Causes of the disease
Antigenic substances that act as allergens causing the disease are xenoproteins, drugs, polysaccharides, and transfused blood products.
Xenoproteins: food proteins, antisera, rubber, bee toxins, protease preparations, endocrine hormones, etc.
Drugs: antibiotics (penicillin, cephalosporins, etc.), anesthetics (lidocaine, procaine, etc.), contrast agents, vitamins (e.g., vitamin B1), etc.
Polysaccharides: e.g. dextrose iron.
Transfusion of blood products: albumin, gammaglobulin, etc.
Predisposing factors
History of allergies; or allergic diseases such as allergic rhinitis, asthma, etc.
Consumption of food of unknown origin.
Bee stings.
Pathogenesis
Antibodies are produced when the allergen enters the organism for the first time.
When the allergen enters the organism again, it can quickly bind to the antibody, resulting in the rapid release of a large number of biologically active substances from the sensitized cells.
These biologically active substances lead to dilation of capillaries throughout the body, congestion and edema in several organs; at the same time, the effective circulating blood volume decreases, blood pressure drops abruptly, and the patient rapidly enters a state of shock.
Symptoms
Main Symptoms
Anaphylaxis may present skin and mucous membrane manifestations, respiratory tract obstruction symptoms, circulatory failure manifestations, change of consciousness, and so on.
Skin and mucous membrane manifestations
Flushing of the skin.
Rash and urticaria with itching.
Decrease in skin temperature with cold sweating.
Respiratory tract obstruction
Edema of the uvula and larynx with sensation of obstruction in the throat.
Chest tightness and shortness of breath.
Wheezing: a continuous, long lasting, musical additional sound produced by breathing.
Cyanosis: an increase in the number of reduced hemoglobin cells in the blood, giving the skin and mucous membranes a cyanotic change.
Asphyxia: manifested by dyspnea, rapid heartbeat, and cyanosis of the skin and mucous membranes.
Circulatory failure manifestations
Palpitations, sweating, pallor.
Cold limbs, rapid drop in blood pressure, loss of pulse.
In severe cases, cardiac arrest may occur.
Digestive system manifestations
Nausea, vomiting.
Abdominal pain, diarrhea.
Altered consciousness
Early on, there is a sense of fear, irritability, dizziness and headache.
Unconsciousness or complete loss of consciousness (coma).
Convulsions: rapid muscle twitching occurs.
Urinary manifestations
Patients may experience urinary incontinence as a result of bladder smooth muscle contraction.
Medical care
Department of Medicine
Emergency Department
If symptoms such as skin flushing, itching, rash, chest tightness, shortness of breath, wheezing, pallor, cold and clammy skin, irritability, etc. occur, it is recommended to go to the Emergency Department immediately, or call 120 emergency for help.
Preparation for medical treatment
Preparation for medical consultation: registration, preparation of information, frequently asked questions
Tips for seeking medical treatment
Before seeking medical treatment, it is recommended to get away from allergens and sensitizing environment immediately.
Family members are advised to help the patient to keep the airway open.
If cardiac arrest occurs, perform cardiopulmonary resuscitation (CPR) immediately.
Preparation Checklist
Symptom Checklist
Pay particular attention to the time of onset of symptoms, special manifestations, etc.
Are there symptoms such as skin flushing and itching?
Are there symptoms such as chest tightness, shortness of breath, wheezing, cyanosis, palpitations, etc.?
Are there symptoms such as coldness of the limbs and pallor?
Under what circumstances do these symptoms occur?
Medical History Checklist
Is there a history of allergies?
Is there a history of allergen exposure (medication, eating specific foods, etc.)?
Are there any insect bites?
Checklist
Test results from the last 6 months, which can be brought with you to the doctor’s office
Laboratory tests: allergen intradermal test.
Medication list
Medication used in the last 3 months, if available in boxes or packages, bring with you to the doctor’s office
Antibiotics: penicillin, cephalosporin, etc.
Anesthetics: lidocaine, procaine, etc.
Contrast media.
Vitamins: vitamin B1.
Diagnosis
Diagnosis is based on
medical history
History of allergy.
Have a history of allergen exposure.
Suffering from allergic diseases such as asthma, allergic rhinitis.
Clinical manifestations
Symptoms
Skin flushing, rash, itching.
Chest tightness, shortness of breath, wheezing, cyanosis.
Palpitations, sweating, cold limbs, pallor.
Unconsciousness, convulsions.
Physical signs
Decrease in blood pressure.
Cold clammy skin.
Loss of consciousness.
Allergen testing
Clinically, no special tests are usually needed for anaphylaxis. However, allergen testing after recovery can determine what substances caused the allergy and avoid a recurrence.
Intradermal test
Screening for suspected allergens.
Localized erythema of 1 to 1.5 cm in diameter suggests allergy to the allergen.
Serum Specific IgE
Checks the body’s reaction to a specific allergen.
Detection of IgE that binds to a specific allergen identifies the allergen of a rapid-onset allergic reaction.
Differential Diagnosis
Anaphylaxis needs to be differentiated from post-injection vasovagal syncope, hypoglycemia, and angioedema.
Post-injection vasovagal syncope
Similarities: both may present with clinical manifestations such as unconsciousness and decreased blood pressure.
Differences:
Post-injection vasovagal syncope occurs immediately after injection, without itching as well as rash, syncope, and can be improved after lying down, and the pulse is slow although the blood pressure drops.
Patients with anaphylaxis may have skin flushing, itching, dyspnea, asphyxia, and even cardiac arrest.
Hypoglycemia
Similarity: Both may present with symptoms such as unconsciousness and pallor.
Differences:
Hypoglycemia mostly occurs after hunger or exertion, and can be relieved after rest, lying down, or drinking sugar water/injecting glucose. Patients with a past history of similar conditions may resolve after oral intake of sugary foods.
Patients with anaphylaxis have a history of allergen exposure, and patients may present with a drop in blood pressure and convulsions. Rapid glucose measurement helps in differential diagnosis.
Angioedema
Similarities: Both may present with symptoms such as skin flushing.
Differences:
Angioedema is a hereditary disease, patients may develop under the stimulation of non-specific factors such as trauma, infection, etc., most of them have a family history, and usually do not have a drop in blood pressure.
Patients with anaphylaxis have a history of allergen exposure, and patients may present with symptoms such as a drop in blood pressure and convulsions.
Treatment
Aim of treatment: to control the progress of the disease and save the patient’s life.
Treatment principle: remove the allergens and carry out effective resuscitation.
General treatment
Discontinue or remove the allergen immediately
If it is caused by drug injection, the drug should be stopped immediately.
If it is an insect bite, the local skin should be examined, and when a poisonous sting is found to remain, a blunt instrument can be used to scrape it off, avoiding the use of pliers to clip it out, so as to prevent more allergenic substances from being squeezed into the organism.
Anti-shock position
Lay the patient flat, elevate the lower limbs to increase the volume of return blood.
In the case of a pregnant woman, the lateral position can be used to minimize the compression of the inferior vena cava by the gestating uterus.
Oxygenation and maintenance of respiratory patency
Routinely give high-flow oxygen.
When hoarseness and stridor occur, tracheal intubation should be performed as soon as possible. Delayed intubation may result in rapid deterioration with progressive stridor, vocal difficulties, and laryngeal edema.
Replenish blood volume
Restoring and maintaining adequate blood volume is an important part of rescuing anaphylaxis.
If the patient is hypotensive and unresponsive to epinephrine, isotonic crystalloid should be given to expand blood volume.
Cardiopulmonary resuscitation
Cardiopulmonary resuscitation (CPR) should be performed immediately if cardiac or respiratory arrest occurs.
In case of sudden loss of consciousness, tap the patient’s shoulder and call out to determine whether he/she is conscious or not, and at the same time touch the carotid artery to determine whether there is any pulsation. If there is no response and there is breathing abnormality or no respiration, it can be determined that the patient is in cardiac arrest, and cardiopulmonary resuscitation (CPR) should be carried out.
Medication
Adrenaline
It is a conventional emergency drug, which can cause vasoconstriction of most tissues and organs of the body, thus raising blood pressure and reducing edema of the mucous membrane of the trachea.
When using epinephrine, the patient’s vital signs and reactions should be closely monitored, and the drug must be diluted to avoid serious adverse effects of overdose.
Adverse effects such as tissue ischemia, cardiac arrhythmias, and dyspnea may occur with epinephrine administration.
Glucocorticoids
May increase the effect of epinephrine and are used for antiallergic and elevated blood pressure.
Common drugs include dexamethasone, methylprednisolone, and hydrocortisone.
Adverse effects such as infection, gastrointestinal irritation, agitation, insomnia, and electrolyte disturbances may occur with use.
Pressure-boosting drugs
After the use of epinephrine and adrenocorticotropic hormone, the blood pressure still can not return to rise, can be used to raise the pressure of the drug.
Common drugs: mesalamine, dopamine.
Do not inject intramuscularly or subcutaneously, so as to avoid ischemic necrosis of the injection site.
Antihistamines
May reduce allergic symptoms.
Common drugs: Diphenhydramine hydrochloride, cimetidine.
Adverse reactions such as dizziness, lightheadedness, nausea, vomiting, lack of appetite and granulocytopenia may occur after use.
Bronchial antispasmodics
Used in patients with bronchospasm.
Common drugs: salbutamol, ipratropium bromide.
Adverse effects such as angioneurotic edema, headache, and tachycardia may occur with use.
Treatment of cardiac arrest
After cardiac arrest, cardiopulmonary resuscitation, rapid volume expansion, and the use of adrenal medications are the basis of treatment, in addition to treating the airway and maintaining oxygen supply.
Rapid volume expansion
Significantly insufficient blood volume requires large amounts of fluid replacement in a short period of time.
Four to eight liters of isotonic crystalloid can be pressurized.
Intravenous administration of high doses of epinephrine
In the event of cardiac arrest, a high dose of epinephrine should be given rapidly intravenously.
Aggressive prolonged cardiopulmonary resuscitation
Patients with anaphylaxis are often young and without significant cardiac or vascular disease.
Rapid correction of vasodilatation and hypovolemia often results in successful resuscitation.
Aggressive antishock and prolonged cardiopulmonary resuscitation can maintain a more adequate supply of oxygen to vital organs.
Prognosis
Cure
Anaphylaxis has a poor prognosis and should be treated aggressively with early and timely detection.
If timely detection and administration of first aid is not possible, the patient may die due to bronchospasm, laryngeal edema, and other causes such as asphyxia.
Prognostic factors
Early diagnosis and early treatment: If early and timely diagnosis can be made, conservative treatment can be provided, and a better prognosis can often be obtained.
Patient’s condition: The prognosis is better for those who have late onset of anaphylaxis after exposure to antigens. Certain patients who are highly sensitized and develop flash anaphylaxis have a poorer prognosis.
Presence of underlying disease: In patients with coronary artery disease, anaphylaxis occurs and myocardial infarction may occur due to plasma concentration and drop in blood pressure.
Those with significant neurologic symptoms are prone to residual complications after recovery from cerebral hypoxia.
Daily
Daily management
Dietary management
For anaphylaxis caused by food allergy, patients are advised to try to focus on natural foods and avoid contact with or consumption of foods that cause allergy.
Life Habits
Live a regular life, pay attention to rest and avoid exertion.
Keep a good mood.
Avoid strenuous exercise during the recovery period.
Follow-up
Regular review helps to detect relapse and aggravation of the disease in time and adjust the treatment plan in time.
It is recommended to follow the doctor’s instructions for follow-up. If there is a change in the condition, consult a doctor immediately.
Allergen intradermal testing or serum-specific IgE testing may be required for follow-up.
Prevention
Measures to prevent anaphylaxis mainly include avoidance of drug abuse, asking for a history of allergy, skin sensitization test, vigilance and observation to prevent a second shock.
Avoidance of drug abuse
It is an important measure to prevent drug anaphylaxis.
Physicians should strictly grasp the principles of drug use, use drugs according to the indications, and avoid drug abuse.
Ask for allergy history
Before applying the drug, it is necessary to ask whether there is a history of allergy, such as urticaria, asthma, eczema and so on.
If there is a history of allergy, vigilance should be exercised when using the drug. If there is already an allergic reaction to a certain drug, it should be prohibited to use it again.
Skin allergy test
Penicillins are subject to skin sensitization tests as required before use.
Patients with a history of allergy, can first scratch test, if negative, and then change to do intradermal test.
Procaine, antitoxin serum, iodine oil agent, etc. should do allergy test.
Increase vigilance and observation
It is recommended that patients with intramuscular injection or intravenous infusion should be observed in the observation room for 20 to 30 minutes after the administration of medication to avoid accidents.
Mosquito bites, such as centipede bites, it is recommended to immediately wash the wound with soapy water or 3% ammonia, 5% to 10% sodium bicarbonate solution. In the event of allergic symptoms such as rashes and asthma, immediately send to the doctor.
Prevention of second shock
Anaphylaxis has already occurred in some patients, and the lack of attention has led to a second shock in a few patients.
It is recommended that the causative drug be labeled most prominently on the medical record card and that the patient and his/her family be informed.