Emergency Management of Rare Anaphylactic Reactions to Hymenoptera Stings

Introduction:

Hymenoptera sting reactions are generally self-limiting and are accompanied by local reactions, edema, pain, and erythema that resolve after some time. However, immediate and delayed hypersensitivity reactions do occur sometimes and may manifest as some unusual and atypical symptoms. These atypical features vary from conventional hypersensitivity features as they involve unusual organs. Although the atypical presentations are rare, clinicians should have an insight into the possible rare anaphylactic reactions associated with Hymenoptera stings for effective management of the case.

What Are Hymenoptera Stings?

The insects like bees, wasps, yellow jackets, hornets, and imported fire ants that cause most of the serious sting-related reactions belong to the order Hymenoptera. Patients with venom allergy are more prone to encounter serious systemic allergic reactions like anaphylaxis, which can turn out to be fatal at times.

What Causes Allergic Reactions Following Hymenoptera Stings?

• Hymenoptera stings inject venom into target tissues, triggering allergic reactions.

• The venom contains allergens in the form of a mixture of smaller, low-molecular-weight substances such as proteolytic enzymes (hyaluronidase, proteases, phospholipase, acid phosphatase), lipids, carbohydrates, and high-molecular-weight proteins.

• Local inflammatory reactions are caused by the low-molecular-weight components, and systemic reaction (anaphylaxis) is caused by the high-molecular-weight components.

• Once the proteolytic enzymes of the venom come in contact with the target tissue, the surrounding skin of the host is degraded, which stimulates mast cells to release histamine and causes basophilic activation, leading to vasodilation and thus the process of inflammation (edema, pain, erythema, and warmth) is initiated.

• People having performed antibodies to high-molecular-weight components of the venom develop IgE-mediated anaphylactic reactions, including systemic vasodilation, angioedema, urticaria, hypotension or shock, and death.

What Are the Unusual Presentations of Hymenoptera Stings?

Unusual presentations of Hymenoptera stings can be classified into the following:

Local Reactions Following Unusual Localization of the Sting:

1. Eyeball Involvement:

• Conjunctivitis.

• Anterior uveitis (inflammation of the middle layer of the eye).

• Corneal injuries.

2. Oropharynx Involvement: Upper airway obstruction due to sting-induced edema (tissues filled with fluid).

Reactions With Atypical Signs and Symptoms:

1. Nervous System:

• Cerebral ischemia (an acute brain injury that occurs due to improper blood flow.

• Seizures.

• Demyelinating disorders of the central and peripheral nervous system.

2. Myocardium:

• Myocardial ischemia (heart attack).

• Heart failure.

3. Lung or Abdominal Involvement: Hemorrhages.

4. Muscles:

• Rhabdomyolysis (a condition in which muscle tissue degenerates, leading to muscle death.

• Compartment syndrome (a serious condition in which pressure builds under tissues due to swelling or internal bleeding).

5. Kidneys:

• Acute nephrotic tubular necrosis (a condition in which the tubular cells of the kidney are damaged, leading to kidney failure (secondary to rhabdomyolysis.

• Acute immune-led interstitial nephritis (refers to swelling or inflammation of the tissues surrounding the tubular cells of the kidney).

6. Other Organ Involvement:

• Autoimmune thrombocytopenia (a condition in which the immune system attacks platelet cells and causes a decrease in the platelet count).

• Skin and soft tissue necrosis.

7. Multi-Organ Involvement Due to Toxic Reactions After Unusual Massive Stings:

• Acute kidney failure.

• Rhabdomyolysis.

• Hemolysis (breakdown of the blood vessels).

• Liver injury.

• Coagulopathy (bleeding disorder).

Who Is at Risk of Undergoing Allergic Reactions to Hymenoptera Stings?

• Short intervals between the sting exposure pose a high risk of impending systemic reaction with the latest encounter. The risk declines with the increase in intervals. However, the risk remains in the range of 20 to 30 percent even after ten years.

• Beekeepers are at high risk of venom sensitization.

• Elderly people are at high risk of encountering severe systemic manifestations when compared to children.

• People suffering from cardiovascular diseases or under beta-blockers are at increased risk of systemic reactions to repeated stingings.

• Patients with mastocytosis (mast cell disorders associated with abnormal mast cell proliferation) are at increased risk of fatal sting reactions.

• Patients with increased serum tryptase levels are also more prone to encounter severe anaphylactic reactions following a sting encounter.

How Are Hymenoptera Sting Reactions Diagnosed?

• As the anaphylactic or other systemic reactions following Hymenoptera stings are rare, there is no specific guideline protocol for the management.

• A detailed history of sting reaction should be elicited, which includes the number and timing of sting reactions, the severity of the symptoms, the time interval between the sting and the onset of symptoms, any emergency treatments obtained, the site of the sting, whether the sting is retained or has been removed, whether the patient comes under occupational risk, any risk factors present for repeated re-stings, tolerated stings after the first systemic reactions, and other allergies.

• Hymenoptera venom allergy (HVA) testing should be advised to detect IgE-induced systemic clinical features due to the activation of mast cells and basophils.

• Patients need to be educated to report any new sting encounters as soon as possible to make sure that the treatment is not delayed, as the symptoms can be the same as the previous ones.

How Are Hymenoptera Sting Reactions Treated?

• Administering glucocorticoids is beneficial in neurological systemic reactions because of their anti-inflammatory and immunomodulatory effects.

• Toxic reactions following massive sting encounters present as a medical emergency and need to be managed effectively.

• There is no antidote for Hymenoptera venom allergy.

• The primary principles involved in managing Hymenoptera massive sting reactions are as follows,

1. Hyponatremia should be corrected to prevent renal ischemia.2. The toxic wastes and heme proteins should be shed from the systemic or renal circulation.3. Hemodialysis and plasma exchange should be carried out to lower the chances of direct venom toxicity by eliminating toxic wastes, correcting electrolyte imbalance, and heme protein clearance from the kidney and other organs.

How Can One Prevent Hymenoptera Sting Reactions?

1. People who are allergic to Hymenoptera stings and who are at high risk of systemic reaction encounters can take the following measures:

• Should avoid walking in bare feet.

• Ensure that the whole body is covered without exposing arms and legs.

• Avoid bright and floral printed costumes.

• Avoiding strong perfumes.

• Ensure that the eatables and the area are free of flying insects before eating.

• Keep the eatables covered, and make sure they are free of insects when eating outdoors.

• Keeping the windows shut while driving.

2. If accidental exposures occur, the following measures can be taken:

• Do not try hitting the bees, as they can sting in defense.

• Try to move out of the place slowly if a bee is flying around.

• Remain calm, and do not panic if a bee flies on you, as it usually goes away after a few seconds.

• Call a local pest control expert to remove a bee or wasp nest found in the houses or gardens.

Conclusion:

Although anaphylactic and other systemic reactions to Hymenoptera stings are rare, clinicians and pediatricians should be well-versed in the possible clinical manifestations and their complications for better management of the cases. One can avoid accidental or occupationally related bee encounters by taking prior precautionary measures. Further studies are required to understand the pathogenesis, unusual presentations, and systemic complications to improve the diagnostic and management protocols.