Hymenoptera Stings

Background

In the United States alone,anaphylaxis accounts for approximately 500 deaths each year and significant morbidity. Hymenoptera envenomation is a major contributor to these statistics.

The order Hymenoptera includes bees, hornets, wasps, yellow jackets, and ants. More than 14,000 species are represented. Honeybees and bumblebees belong to the Apidae family, while hornets, wasps, and yellow jackets belong to the Vespidae family. Ants belong to the family Formicidae.

Among winged Hymenoptera, envenomation is used for killing or paralyzing prey and for defense. The stinger, therefore, is used repeatedly. Only the honeybee leaves the stinger, venom gland, and other internal organs attached at the site of the sting.

Hymenoptera are present on all land areas of the world, except the polar regions, during some or all seasons. In Africa, domesticated honeybees have been crossed with more aggressive wild honeybees. These Africanized bees (Apis mellifera scutellata) have been introduced into South America and, from there, have migrated to North America, including the southern United States. Their venom is no more potent than that of other honeybees, but they are more aggressive and tend to swarm, causing multiple stings.

Fire ants (Solenopsis invicta) also are present in the southern United States, having migrated from South America. In Florida and Louisiana, they have replaced many of the indigenous species.

Pathophysiology

The venom of winged Hymenoptera contains over 30 individual compounds. These include biogenic amines (eg, acetylcholine, dopamine, histamine, norepinephrine, serotonin), polypeptides or protein toxins (eg, apamin, melittin, kinins), and enzymes (eg, hyaluronidase, phospholipases). The venom of fire, or stinging, ants consists of small amounts of low molecular weight protein and is as much as 95% alkaloid, which is uncommon in ant species.

Reactions to envenomation may be directly toxic, either local or systemic, or allergic, either localized or anaphylactic. Allergic reaction to fire ant venom is unusual. Strong cross-reactivity to the allergic reactions occurs within a family, but less so between families. The venom of bees and wasps has been reported to be more potent during the autumn months.

Frequency

United States

Hymenoptera envenomation affects nearly every person during his or her lifetime and 10-20% of the population annually. From 300-500 deaths occur annually, almost all are secondary to anaphylaxis.

International

The international incidence of Hymenoptera envenomation is related to region and local custom. In Africa, the harvesting of honey involves collecting honey from wild bees, which usually involves destroying the hive and results in subsequent exposure to hundreds of bees. In traditional Chinese herbal medicine, apiotherapy involves mixing bee venom with ointment and applying it to the skin or eyes, which may result in allergic reactions.

Age

Children with a history of severe reaction may have only slightly higher risk of anaphylaxis when they reach adulthood compared to the general population, while history of severe reaction as an adult is associated with a rate of anaphylaxis of approximately 60%.

Treatment

Medical Care

• The treatment of simple envenomations seldom requires more than local care.
• • Ice usually is helpful, and pain control can be achieved with ibuprofen or acetaminophen.
  • Narcotics occasionally may be necessary.
  • Itching can be controlled with topical or oral antihistamines.
  • If the stinger is present, it should be removed promptly to avoid continued envenomation. This is best accomplished by scraping with a scalpel or flat card. Using tweezers may squeeze the attached venom sack, injecting more venom.
• Acute Hymenoptera envenomations with generalized reactions, urticaria, or other systemic signs usually require parenteral therapy with antihistamines (diphenhydramine) and/or epinephrine.
• • Prompt and repeated use of epinephrine may be lifesaving and should be administered as often as every 20-30 minutes, if needed, or even by continuous intervenous infusion.
  • Inhaled bronchodilators may be useful in cases where bronchospasm is resistant to epinephrine or where preexisting asthma is exacerbated by the envenomation.
  • The use of corticosteroids parenterally or orally may be useful in long-term management.
  • Addition of an H2 histamine receptor-blocking drug to the H1 antihistamine regimen may assist in controlling urticaria and itching.
  • Liberal use of crystalloid intravenously, and even pressors in cases of shock (anaphylactoid or anaphylaxis), may be necessary.
  • Increased doses of epinephrine or other pressor agents may be necessary if patients are taking beta-blockers or calcium channel blockers.
  • If narcotics are necessary for control of pain in cases of anaphylaxis, fentanyl is the preferred agent because it is not associated with the release of endogenous histamine as are other narcotics, particularly meperidine.
  • Respiratory distress may develop very rapidly, and airway management is critical and should not be delayed if obvious clinical deterioration occurs.
  • If laryngeal edema is present, endotracheal intubation may be difficult or impossible and cricothyroidotomy or tracheotomy may be necessary emergently.
  • If a generalized reaction or anaphylaxis does not resolve with treatment, consideration should be given to in-hospital observation in a monitored unit.
• The management of delayed hypersensitivity reactions is dictated largely by the presentation.
• • In these cases, considering the possibility of Hymenoptera envenomation as an etiology is necessary because envenomations are seldom obvious.
  • The prognosis may be improved if envenomation is the cause, but therapy is unchanged.

Medication

The goals of pharmacotherapy are to reduce morbidity and to prevent complications.

Drug Category: Adrenergic agonist agents

These agents relieve reversible bronchospasm by relaxing smooth muscles of the bronchi.

Drug Name	Epinephrine (Adrenalin, Bronitin, EpiPen)
Description	DOC for treating anaphylactoid reactions. Has alpha-agonist effects that include increased peripheral vascular resistance, reversed peripheral vasodilatation, systemic hypotension, and vascular permeability. Beta-agonist effects include bronchodilatation, chronotropic cardiac activity, and positive inotropic effects.
Adult Dose	0.15-0.3 mg SC or 0.2-1 mg IV; may repeat q20-30min if indicated; may give by a self-injecting device (0.15 or 0.3 mg) as continuous IV infusion at 1-4 mcg/min
Pediatric Dose	0.01-0.1 mg/kg SC/IV
Contraindications	Documented hypersensitivity; cardiac arrhythmias, angle-closure glaucoma; local anesthesia in areas such as fingers or toes because vasoconstriction may produce sloughing of tissue; during labor (may delay second stage of labor)
Interactions	Increases toxicity of beta-blocking and alpha-blocking agents and that of halogenated inhaled anesthetics
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Caution in elderly, prostatic hypertrophy, hypertension, cardiovascular disease, diabetes mellitus, hyperthyroidism, and cerebrovascular insufficiency; rapid IV infusions may cause death from cerebrovascular hemorrhage or cardiac arrhythmias

Drug Category: Antihistamines

Act by competitive inhibition of histamine at H1 receptor. This mediates the wheal and flare reactions, bronchial constriction, mucous secretion, smooth-muscle contraction, edema, hypotension, CNS depression, and cardiac arrhythmias.

Drug Name	Diphenhydramine (Benylin, Benadryl)
Description	For symptomatic relief of symptoms caused by release of histamine in allergic reactions.
Adult Dose	25-75 mg PO/IV/IM q6-8h prn; not to exceed 400 mg/d
Pediatric Dose	1-2 mg/kg PO/IV/IM q6-8h prn
Contraindications	Documented hypersensitivity; MAOIs; AV block greater than first degree
Interactions	Potentiates effect of CNS depressants; due to alcohol content, do not give syrup dosage form to patient taking medications that can cause disulfiramlike reactions
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	May exacerbate angle-closure glaucoma, hyperthyroidism, peptic ulcer, or urinary tract obstruction; xerostomia may occur

Drug Category: Corticosteroids

Decrease late immune-mediated complications.

Drug Name	Methylprednisolone (Adlone, Solu-Medrol, Depo-Medrol)
Description	May decrease inflammation by reversing increased capillary permeability and suppressing PMN activity. Indicated for severe, prolonged, or anaphylactic reactions
Adult Dose	125 mg IV q6h for up to 5 d; not to exceed 1 g; higher dose range probably is not warranted routinely
Pediatric Dose	0.1-2 mg/kg IV q6h for up to 5 d
Contraindications	Documented hypersensitivity; viral, fungal, or tubercular skin infections
Interactions	Coadministration with digoxin may increase digitalis toxicity secondary to hypokalemia; estrogens may increase levels; phenobarbital, phenytoin, and rifampin may decrease levels (adjust dose); monitor for hypokalemia with coadministration of diuretics
Pregnancy	C - Safety for use during pregnancy has not been established.
Precautions	Hyperglycemia, edema, osteonecrosis, peptic ulcer disease, hypokalemia, osteoporosis, euphoria, psychosis, growth suppression, myopathy, and infections are possible complications of glucocorticoid use

Drug Name	Prednisone (Deltasone, Orasone, Meticorten)
Description	May decrease inflammation by reversing increased capillary permeability and suppressing PMN activity. Indicated for severe, prolonged, or anaphylactic reactions.
Adult Dose	40-60 mg PO q6h; may be given as a tapering schedule over 4-10 d after discharge
Pediatric Dose	1-2 mg/kg PO in divided doses
Contraindications	Documented hypersensitivity; viral infection, peptic ulcer disease, hepatic dysfunction, connective tissue infections, and fungal or tubercular skin infections; GI disease
Interactions	Coadministration with estrogens may decrease prednisone clearance; concurrent use with digoxin may cause digitalis toxicity secondary to hypokalemia; phenobarbital, phenytoin, and rifampin may increase metabolism of glucocorticoids (consider increasing maintenance dose); monitor for hypokalemia with coadministration of diuretics
Pregnancy	B - Usually safe but benefits must outweigh the risks.
Precautions	Abrupt discontinuation of glucocorticoids may cause adrenal crisis; hyperglycemia, edema, osteonecrosis, myopathy, peptic ulcer disease, hypokalemia, osteoporosis, euphoria, psychosis, myasthenia gravis, growth suppression, and infections may occur with glucocorticoid use