div class=”ChapterContextInformation”>
16. Anaphylaxis
16.1 Introduction
Anaphylaxis is a potentially life-threatening hypersensitivity reaction involving multiple organs and requires immediate management [1, 2]. The word “anaphylaxis” is derived from the Greek words ana (meaning backward) and phylax (meaning to protect or guard) implying that the agent administered for its protective effect has on the contrary proved harmful. True definition of anaphylaxis refers only to IgE-mediated hypersensitivity reaction (Type 1), while non IgE-mediated reactions are termed as “anaphylactoid reactions.” However it is difficult to distinguish between two conditions clinically. Also the initial management of both these conditions is also identical. The World Allergy Organization has now classified anaphylaxis into immunologic, immunoglobulin E (IgE)-mediated, and non-immunologic reactions [3]. Incidence of anaphylaxis during pregnancy is estimated to be around 1 in 30,000 pregnancies [4].
Pregnancy involves several hospital visits with administration or ingestion of medications which can sometimes cause anaphylaxis. Also the immunological changes that occur during the pregnancy can predispose women to anaphylaxis [5].
Anaphylaxis during pregnancy can be devastating and can endanger the life of both the mother and the fetus by causing hypoxic-ischemic encephalopathy and permanent central nervous system damage [6].
16.2 Pathophysiology [7–9]
Anaphylactic and anaphylactoid reactions occur because of release of mediators from mast cells and basophils following their degranulation due to antigen-antibody reaction. These mediators include histamine, tryptase, heparin, chymase, and cytokines and arachidonic acid metabolites (e.g., prostaglandins and leukotrienes), which are stored in the granules of mast cells and basophils.
Classical anaphylactic reaction occurs following reexposure to an antigen to which the individual has already been sensitized due to previous exposure in the past. During the primary exposure to antigen, IgE antibody is produced, and the substance which induces this response is called an “antigen,” and the individual is now said to be sensitized to that particular antigen. These IgE antibodies bind to the high-affinity IgE receptor on the surface of mast cells and basophils. Subsequent reexposure to the same antigen results in antigen-antibody reaction, and the antigen-bound IgE antibodies cause degranulation of mast cells and basophils and release of histamine which is the primary mediator of anaphylaxis along with prostaglandins and leukotrienes. Binding of histamine to its H1 and H2 receptors primarily as well as prostaglandins and leukotrienes to their respective receptors is responsible for the widespread systemic effects seen in anaphylaxis. Other pathways active during anaphylaxis are the complement system, the kallikrein-kinin system, the clotting cascade, and the fibrinolytic system.
Activation of a specific subset of lymphocyte lineage (CD4 + Th2 T cells) is believed to be responsible for IgE production. CD4 + T cells have been classified as Th1 type or Th2 type. Th1 is responsible for cellular immunity and production of interferon gamma, while Th2 plays an important role in humoral immunity as well as perpetuation of allergic response. Multiple factors including genetic and environmental factors along with type and quantity of immune trigger determine what type of response a particular individual would develop. Activation of Th2 cells rather than the Th1 lineage is believed to be responsible for the development and perpetuation of allergic responses.
16.3 Etiology
The etiological causes of anaphylaxis during pregnancy are the same as with the nonpregnant population [5].
- 1.
Food allergy—Peanut allergy is the most common food allergy. Other foods commonly associated with anaphylaxis include cow’s milk, eggs, shellfish, soy, wheat, and tree nuts.
- 2.
Medications—The most common drugs which cause anaphylaxis are the group of beta-lactam antibiotics (penicillin) particularly when given by parenteral route. These drugs are often used to prevent maternal infection when given prior to/during cesarean delivery or neonatal group B streptococcal infection. Other drugs include cephalosporins, sulfonamides, NSAIDs, aspirin, insulin, general anesthetics, insulin, progesterone, blood products, biological agents, radiocontrast materials, and immunotherapy. Also iron compounds like iron dextran and iron sorbitol injections which are commonly used to treat anemia during pregnancy are known to cause occasional anaphylactic reactions. Fortunately newer iron preparations like iron sucrose are less known to cause such reactions. Various B complex injections (B1, B6, B12) have also reported to cause such reactions.
- 3.
Latex—Sensitization and subsequent anaphylactic reaction to latex can occur during various gynecological and obstetric procedures.
- 4.
Hymenoptera venoms—Insect bite from honeybees, wasps, fire ants, etc. can also elicit IgE-mediated anaphylaxis.
- 5.
IgG and immune complex-mediated reactions can occur to blood and blood products commonly used in transfusion. Partially unbound iron released from iron sucrose can increase the oxidative stress and cause adverse reactions.
Most common cause of anaphylaxis during labor and delivery is prophylactic injection of a penicillin or cephalosporin to prevent neonatal group B streptococcal (GBS) infection or to prevent maternal infection after cesarean delivery [10–12].
16.4 Diagnosis
Anaphylaxis is diagnosed when there is rapid development of symptoms and signs following history of exposure to a likely or known allergen and its subsequent evolution over period of minutes to hours [13]. The diagnosis of anaphylaxis is primarily clinical. The diagnosis can be made in the presence of clinical features even if laboratory tests are negative. Clinical diagnosis is made based on detailed history and development of characteristic features (symptoms and signs) which are often sudden in onset and rapidly progressing. The characteristic symptoms typically occur within a few minutes to hours after exposure to known or likely antigen. Symptoms often involve more than one system, most common being skin/cutaneous (80–90%), respiratory (70%), cardiovascular, and/or gastrointestinal (45–50%) cases.
Features of anaphylaxis in pregnancy include intense itching in the vulvar and vaginal areas, uterine cramps, low back pain, preterm labor, and fetal distress. There is mostly history of exposure to known or likely antigen. The severity of symptoms and signs may vary depending on type and quantum of allergen. Hypotension and shock may not occur in all cases although more than one organ system is typically involved.
16.4.1 Diagnostic Criteria
- 1.
First, in women with no prior history of anaphylaxis or in the absence of any know allergen, anaphylaxis is diagnosed by a rapid onset (minutes to hours) of a reaction that involves the skin, mucosal tissue, or both (generalized urticaria, itching or flushing, swollen lips, tongue, and/or vulva), alongside at least one of the following symptoms:
Respiratory compromise—dyspnea, features of bronchospasm, stridor, reduced peak expiratory flow, and hypoxemia.
Reduced blood pressure or features suggestive of end-organ dysfunction like hypotonia, syncope, incontinence, or collapse.
- 2.
Second, when after exposure to a likely allergen, occurrence of two or more of the following is within minutes to hours:
Involvement of the skin or mucosal tissue (generalized urticaria, itching or flushing, swollen lips, tongue, and/or vulva).
Respiratory symptoms, dyspnea, features of bronchospasm, stridor, and hypoxemia.
Decreased blood pressure features suggestive of end-organ dysfunction like hypotonia, syncope, incontinence, or collapse.
Persistent features suggestive of gastrointestinal involvement like pain, abdominal cramps, vomiting, etc.
- 3.
Third, on exposure to a known allergen, reduced blood pressure alone is sufficient for the diagnosis of anaphylaxis. Reduced blood pressure is defined as systolic blood pressure of less than 90 mmHg or 30% decrease from woman’s baseline blood pressure.
General and systemic examination findings may vary depending on the severity and the organs involved and may show the following:
General appearance: patient may be anxious, restless, and disoriented.
Respiratory findings: angioedema of the tongue and lips, stridor or wheezing, loss of voice, hoarseness, and tachypnea.
Dermatologic: urticaria (i.e., hives) is the classical skin manifestation which can occur anywhere on the body; angioedema or soft-tissue swelling or erythema can also occur.
Cardiovascular: tachycardia, hypotension, and shock may occur immediately, without any other findings.
Neurological: patient may be disoriented or may be agitated and restless.
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
