Anaphylaxis - Education

Summary

Anaphylaxis is a severe allergic reaction resulting from mast cell and basophil degranulation upon antigen exposure. It can manifest with life-threatening symptoms in respiratory, cardiovascular, and integumentary systems, varying in onset and severity. Common triggers during anesthesia include neuromuscular blockers and antibiotics. Immediate treatment involves calling for help, administering epinephrine, securing an airway, and providing fluids, with histamine blockers and steroids as adjunctive therapies.

Takeaways

• 🚨 Anaphylaxis is a severe allergic reaction resulting from the degranulation of sensitized mast cells and basophils upon antigen exposure.
• 🔬 Mast cells are found in the perivascular spaces of the skin and intestine, while basophils are in the blood.
• 🌟 Immunoglobulin E (IgE) is produced on initial exposure to an antigen and binds to the effector cells' surface, triggering a response on subsequent exposures.
• 💊 Physiologically active mediators like histamine, tryptase, and platelet-activating factor are released during anaphylaxis.
• 🌡 Histamine is a key inflammatory mediator stored in mast cells and basophils, causing vasodilation, increased vascular permeability, and other symptoms.
• 🚑 Symptoms of anaphylaxis can be life-threatening, affecting the respiratory, cardiovascular, and integumentary systems.
• 💉 An anaphylactic reaction can occur on first exposure to certain drugs, such as anaesthetics, due to cross-reactivity.
• 🕒 The onset and severity of anaphylactic symptoms can vary, complicating diagnosis, and may be masked by general anesthesia or surgical drapes.
• 📊 Neuromuscular blocking agents are the most common triggers for an anaphylactic reaction during anesthesia, accounting for over 50% of incidents.
• 🏥 Immediate treatment for anaphylaxis is critical and includes calling for help, administering epinephrine, securing an airway, and providing fluids.
• 🛡 Epinephrine is crucial in anaphylaxis treatment due to its hemodynamic effects and ability to stabilize mast cells, reducing mediator release.

Q & A

What is anaphylaxis?

Anaphylaxis is a severe hypersensitivity reaction caused by the degranulation of sensitized mast cells and basophils after exposure to an antigen.

Where are mast cells and basophils typically located in the body?

Mast cells are located in the perivascular spaces of the skin, long intestine, and other tissues, while basophils are found in the blood.

What is the role of immunoglobulin E (IgE) in anaphylaxis?

IgE is produced upon initial exposure to an antigen and binds to the surface of effector cells, such as mast cells and basophils. Upon subsequent exposure, the antigen binds to the IgE, triggering the release of physiologically active mediators.

What are some of the physiologically active mediators released during an anaphylactic reaction?

During an anaphylactic reaction, mediators such as histamine, tryptase, chemotactic factors, platelet-activating factor, prostaglandins, leukotrienes, and cytokines are synthesized and released.

How does histamine contribute to the clinical signs and symptoms of anaphylaxis?

Histamine, stored in granules within mast cells and basophils, is a primary inflammatory mediator that works on receptors to cause vasodilation, increased vascular permeability, contraction of most smooth muscles, cardiac stimulation, and gastric secretions, leading to various symptoms of anaphylaxis.

Which systems of the body are most notably affected by an anaphylactic reaction?

The respiratory, cardiovascular, and integumentary systems are most notably affected by an anaphylactic reaction.

Can an anaphylactic reaction occur on first exposure to certain substances?

Yes, an anaphylactic reaction can occur on first exposure to certain substances, such as anaesthetic medications, due to cross-reactivity among many drugs and commercial household products.

What are some common triggering agents for an anaphylactic reaction during anesthesia?

Neuromuscular blocking agents are the most common triggering agents, accounting for more than fifty percent of incidents. Other causative agents include latex, antibiotics, colloids, hypnotics, contrast media, protamine, and opioids.

What are the signs and symptoms of an anaphylactic reaction?

Signs and symptoms include angioedema, laryngeal edema, hypotension, tachycardia, dysrhythmias, wheezing, bronchospasm, and a shock-like state secondary to severe hypotension.

What is the role of tryptase in an anaphylactic reaction?

Tryptase is an enzyme released from mast cells along with histamine and serves as a positive indicator for an immunologically mediated event when levels are greater than 25 micrograms per liter.

What is the immediate treatment for an anaphylactic reaction?

Immediate treatment includes calling for help, removing potential causative agents, increasing FIO2 to 100%, administering epinephrine, establishing a secure airway, ensuring adequate IV access, and providing a fluid bolus. An epinephrine infusion may be considered if there is no response to initial interventions.

Why is epinephrine a crucial part of anaphylaxis treatment?

Epinephrine is crucial due to its positive hemodynamic effects and its ability to stabilize mast cells and reduce the amount of inflammatory mediator release.

What are some other treatment options for anaphylaxis besides epinephrine?

Other treatment options include vasopressors, beta-2 agonists, histamine blockers, and steroids to counteract the effects of histamine and assist in reversing hypotension refractory to epinephrine and intravascular fluid replacement.