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Hymenoptera Envenomation:
Bees, Wasps, And Ants
Imagine these scenarios:
Paramedics call your emergency department to inform you that they
are transporting a 12-year-old boy who was stung several hundred
times by a swarm of honeybees. The patient is agitated and has innumerable erythematous papular stings to his face and extremities. What
are your immediate priorities, and what are your subsequent concerns
for delayed toxicity?
A 7-year-old girl is brought to triage by her parents after she was stung
a single time by a wasp. She is lethargic with facial swelling and a generalized urticarial rash. In addition, she has respiratory distress with bilateral
wheezes on lung examination, and pulse oximetry demonstrates oxygen
saturations of 87% on room air. How should this life-threatening situation
be managed?
A 2-year-old male is transported to your emergency department after
stumbling into a fire ant nest. He is crying, irritable, and tachycardic but
has no respiratory distress. He has multiple erythematous papules on his
legs that are beginning to form fluid-filled vesicles. What is the treatment
for this envenomation?
S
tinging insects have long been known to cause allergic reactions in humans. The earliest recorded death from an allergic
reaction caused by a stinging insect was that of Pharaoh Menes of
Egypt who died in 2641 B.C. after being stung by either a hornet or
a wasp.1
Bees, wasps, and ants (Figure 1) are stinging insects belonging to
the order Hymenoptera, which is Latin for “membrane-winged.” The
3 families of greatest medical significance within this order are Apidae (honeybees and bumblebees), Vespidae (yellow jackets, hornets,
AAP Sponsor
Martin I. Herman, MD, FAAP,
FACEP, Professor of Pediatrics,
UT College of Medicine, Assistant
Director of Emergency Services,
Lebonheur Children’s Medical
Center, Memphis, TN
Editorial Board
Jeffrey R. Avner, MD, FAAP,
Professor of Clinical Pediatrics
and Chief of Pediatric Emergency
Medicine, Albert Einstein College
of Medicine, Children’s Hospital at
Montefiore, Bronx, NY
T. Kent Denmark, MD, FAAP,
FACEP Residency Director,
Pediatric Emergency Medicine;
Assistant Professor of Emergency
Medicine and Pediatrics, Loma
Linda University Medical Center
and Children’s Hospital, Loma
Linda, CA
June 2008
Volume 5, Number 6
Authors
Sing-Yi Feng, MD
Assistant Professor of Pediatrics, Section of Toxicology,
Division of Pediatric Emergency Medicine, University of
Texas Southwestern Medical Center at Dallas, Children’s
Medical Center of Dallas and the North Texas Poison
Center, Parkland Memorial Hospital, Dallas, TX
Collin Goto, MD
Associate Professor of Pediatrics, Section of Toxicology,
Division of Pediatric Emergency Medicine, University of
Texas Southwestern Medical Center at Dallas, Children’s
Medical Center of Dallas and the North Texas Poison
Center, Parkland Memorial Hospital, Dallas, TX
Peer Reviewers
George Hutchinson, MD, FAAEM
Emergency Medicine Physician, Benton, Arkansas
Joseph Toscano, MD
Attending Physician, Emergency Department, San Ramon
Regional Medical Center, San Ramon, CA
CME Objectives
Upon completing this article, you should be able to:
1. Describe the epidemiology and pathophysiology of
Hymenoptera envenomation.
2. Identify and treat the immediate life-threatening
complications of bee and wasp stings.
3. Understand and manage the delayed complications of
Hymenoptera envenomation.
4. Describe the presentation and management of fire ant
envenomation.
Date of original release: June 1, 2008
Date of most recent review: May 10, 2008
Termination date: June 1, 2011
Time to complete activity: 4 hours
Medium: Print & online
Method of participation: Print or online answer
form and evaluation
Prior to beginning this activity, see “Physician CME
Information” on the back page of this publication.
Michael J. Gerardi, MD, FAAP,
of Chicago, Pritzker School of
of Emergency Medicine and
FACEP Clinical Assistant
Medicine, Chicago, IL
Pediatrics, Loma Linda Medical
Professor, Medicine, University
Center and Children’s Hospital,
Alson S. Inaba, MD, FAAP, PALSof Medicine and Dentistry of
Loma Linda, CA
NF Pediatric Emergency Medicine
New Jersey; Director, Pediatric
Attending Physician, Kapiolani
Brent R. King, MD, FACEP,
Emergency Medicine, Children’s
Medical Center for Women &
FAAP, FAAEM Professor of
Medical Center, Atlantic Health
Children; Associate Professor of
Emergency Medicine and
System; Department of Emergency
Pediatrics, University of Hawaii
Pediatrics; Chairman, Department
Medicine, Morristown Memorial
John A. Burns, School of Medicine,
of Emergency Medicine, The
Hospital, Morristown, NJ
Honolulu, HI; Pediatric Advanced
University of Texas Houston
Ran D. Goldman, MD Associate
Life Support National Faculty
Medical School, Houston, TX
Professor, Department of
Representative, American Heart
Robert Luten, MD Professor,
Pediatrics, University of
Association, Hawaii & Pacific Island
Pediatrics and Emergency
Toronto; Division of Pediatric
Region
Medicine, University of Florida,
Emergency Medicine and Clinical Andy Jagoda, MD, FACEP Professor
Jacksonville, FL
Pharmacology and Toxicology,
and Vice-Chair of Academic
Ghazala Q. Sharieff, MD, FAAP,
The Hospital for Sick Children,
Affairs, Department of Emergency
FACEP, FAAEM Associate Clinical
Toronto, ON
Medicine, Mount Sinai School of
Professor, Children’s Hospital
Mark A. Hostetler, MD, MPH
Medicine; Medical Director, Mount
and Health Center/University of
Assistant Professor, Department
Sinai Hospital, New York, NY
California, San Diego; Director of
of Pediatrics; Chief, Section of
Tommy Y. Kim, MD, FAAP Attending
Pediatric Emergency Medicine,
Emergency Medicine; Medical
Physician, Pediatric Emergency
California Emergency Physicians,
Director, Pediatric Emergency
Department; Assistant Professor
San Diego, CA
Department, The University
Gary R. Strange, MD, MA, FACEP
Professor and Head, Department
of Emergency Medicine, University
of Illinois, Chicago, IL
Adam Vella, MD, FAAP Assistant
Professor of Emergency Medicine,
Pediatric EM Fellowship Director,
Mount Sinai School of Medicine,
New York
Michael Witt, MD, MPH, FAAP
Attending Physician, Division of
Emergency Medicine, Children’s
Hospital Boston; Instructor of
Pediatrics, Harvard Medical
School, Boston, MA Research
Editor
Research Editor
Christopher Strother, MD Fellow,
Pediatric Emergency Medicine, Mt.
Sinai School of Medicine; Chair,
AAP Section on Residents, New
York, NY
Accreditation: This activity has been planned and implemented in accordance with the Essentials and Standards of the Accreditation Council for Continuing Medical
Education (ACCME) through the joint sponsorship of Mount Sinai School of Medicine and Pediatric Emergency Medicine Practice. The Mount Sinai School of Medicine is
accredited by the ACCME to provide continuing medical education for physicians. Faculty Disclosure: Dr. Feng, Dr. Goto, Dr. Hutchinson, and Dr. Toscano report no
significant financial interest or other relationship with the manufacturer(s) of any commercial product(s) discussed in this educational presentation.
Commercial Support: Pediatric Emergency Medicine does not accept any commercial support.
and wasps), and Formicidae (fire ants).2 Hymenoptera
stings cause a wide spectrum of illness ranging from
benign nuisance to life-threatening toxicity and anaphylaxis. It is estimated that anaphylaxis to Hymenoptera species affects up to 0.5% of the U.S. population and is responsible for more than 40 deaths per
year in the United States. 1, 2
Children are frequent victims of this important
group of stinging insects, and very young children
are at increased risk for significant toxicity due to
their inability to escape from multiple envenomations and increased venom delivered per kilogram.
This issue of Pediatric Emergency Medicine Practice
will focus on the evaluation and management of the
child with Hymenoptera envenomation.
literature. However, it is important to note that
there is also a growing body of literature documenting morbidity and mortality resulting from mass
envenomations by Hymenoptera.
Part I. Apidae And Vespidae (Bees
And Wasps)
Epidemiology
Critical Appraisal Of The Literature
The literature review for this article included
PubMed searches for articles related to bee, wasp,
and ant envenomation. The search also included the
terms “Hymenoptera” and “Solenopsis envenomation,”
as well as “bee,” “yellow jacket,” and “Solenopsis
venom.” Further manual searches of references from
key publications and pertinent textbook chapters
provided additional articles for review. Since most
of the major morbidity and mortality from these
envenomations result from allergic reactions and
anaphylaxis, it is not unexpected that many of the
references were published in allergy-immunology
In 2005, 10,792 exposures to bees, wasps, and hornets were reported to U.S. Poison Centers. Over
4000 of these exposures were in children less than 19
years of age. Over 1200 exposures were treated at
a health care facility and 1 death was reported.4 It is
important to note that the true number of exposures
and serious outcomes is much higher than these
numbers would suggest because significant underreporting occurs.
Apidae
Honeybees
Apis mellifera, otherwise known as the honeybee, is
originally a European and African species. Honeybees were introduced to North America by European
settlers for their honey-making abilities. They are
one of the few domesticated insects, and colonies are
maintained in hives in many countries. Feral honeybee colonies usually nest in hollow trees or crevices in
rocks and even in the walls of occupied buildings.3, 5, 6
Figure 1. Taxonomy Of The Order Hymenoptera
Phylum Arthopoda
Class Insecta
Order Hymenoptera
Family Vespidae
(true wasps)
Family Apidae
(bees)
Family Formicidae
(ants)
Subfamily Vespinae
(hornets, yellow
jackets)
Subfamily Apinae
(honey, bumble)
Subfamily
Myrmicinae
Genus Bombus
(bumblebees)
Genus Apis
(honeybees)
Genus Solenopsis
(fire ants)
Adapted from Goldfrank’s Toxicologic Emergencies, Eighth Edition
Pediatric Emergency Medicine Practice © 2008
June 2008 • EBMedicine.net
Bumblebees
Bumblebees (Bombus terrestris) are found mostly in
the Northern hemisphere and are large, slow-moving, noisy bees with hairy bodies and alternating
yellow and black stripes. They usually reside in
small colonies of no more than 200 insects and nest
just under the surface of the ground, often in abandoned mammal burrows. They are non-aggressive
and account for only a small fraction of stings. Bumblebees typically are not involved in mass stinging
and will generally only sting if the nest is threatened
or if they are captured or trapped between skin and
clothing. 3, 6, 7, 10
Bumblebees have long been used in North
America and Europe to pollinate vegetable crops.
Due to their increased use in the agricultural sector,
the incidence of bumblebee stings and occupationally-related anaphylactic reactions to bumblebee
venom has increased.11
Honeybees are small, hair-covered insects with
alternating tan and black stripes. They are relatively
non-aggressive and generally sting only when threatened.7 Fatalities from honeybee stings are fortunately
a rare event. Most fatalities are caused by Type I IgEmediated anaphylactic reactions, but deaths are also
reported following massive envenomation involving
hundreds to thousands of stings.6, 8
Africanized Honeybees (AHBs)
Disease-resistant African bees were imported into
Brazil in the 1950s in the hope of cross-breeding them with honey-producing domestic bees to
increase productivity as well as disease resistance.
However, in 1956, 26 imported queen bees and their
colonies escaped and began interbreeding with local honeybees. The resulting Africanized bees (Apis
mellifera scutella) then proliferated and migrated
through South and Central America. They eventually entered the United States in the 1990s and spread
throughout the southwestern states.5
The Africanized bee usually displays the same
behavioral patterns as the European bee. However,
when AHBs perceive that their hives have been
threatened, they will attack more rapidly and in
greater numbers than their European cousins. AHBs
will also pursue and continuously sting their victims
over greater distances than the domesticated honeybees with distances reported up to 0.6 miles. The
primary risk to the victim is in the sheer number of
stings that the AHB will deliver.5, 6, 8
AHBs also differ from European honeybees by
swarming several times a year compared to European honeybees, which swarm only once or twice
a year. Swarming occurs when new queens are
produced in a colony and part of the colony leaves
with the old queen. This increases the number of
colonies within a given area. Also, AHBs often colonize in unprotected areas where they are more easily
disturbed by humans.5
Africanized honeybees preferentially seek
food, water, and shelter in metropolitan areas of
the Southwestern United States due to the warmer
climate. Africanized honeybees do not establish
colonies well in freezing climates but have the
potential to pose a threat during the warm season
due to inadvertent transport by various forms of
shipping.5, 9
The first reported mass envenomation involving AHBs in the United States occurred in the
spring of 1991 in the lower Rio Grande Valley of
South Texas and resulted in 350 stings. Since their
arrival, there have been 4 deaths associated with
attacks by AHBs in Texas and Arizona. Although
there have been AHB mass envenomation incidents
reported in California, no fatalities have been reported in that state.5
EBMedicine.net • June 2008
Vespidae
Wasps (Yellow Jackets, Hornets)
Wasps are a well-recognized medical concern in
North America and Europe. Wasps often build
their nests close to human dwellings under roofs,
behind shutters, and in dryer vents.3, 12 Yellow jackets and hornets are wasps belonging to the subfamily Vespinae.
Yellow jackets are usually 10-15 mm in length.
They build and live in nests in the walls of occupied
buildings or in the ground. Yellow jackets maintain
colonies of several hundred to several thousand
individuals. They are also strongly attracted to garbage and other rotting organic materials.3, 6, 12
Hornets usually live in large paper-like nests
built hanging in trees or under branches. Hornets
are usually 15-40 mm in length. They also maintain
colonies of several hundred to thousands of individual insects and are theoretically more dangerous due to greater venom injection capability and
venom toxicity. 6, 12
Etiology
Apidae
Venom Apparatus And Stinger Mechanism
Members of the Apidae family (bees) can only sting
once because their stinger is a modified ovipositor
that resides in the abdomen. The stinger is barbed
and is attached to a venom sac. After the sting,
the bee is disemboweled as the stinger detaches
and takes along with it the distal segment of the
bee’s intestinal tract including nerves, muscles, and
venom sac. After it is detached, the stinger’s nerves
and muscles continue to work the barb deeper into
the flesh of the victim. A valve and piston pumps
venom from the venom sac through the stinger and
into the wound.13
Pediatric Emergency Medicine Practice © 2008
Vespidae
Venom Apparatus
Vespidae do not eviscerate after stinging their
victims because their stinger is smooth instead of
barbed. The venom apparatus consists of 2 acid
glands: an alkaline gland and a venom sac, which
is connected to a stinger. The distal part of the
acid gland secretes the venom while the proximal part transports the secretions to the venom
sac, which acts as a reservoir. The venom moves
to the alkaline gland, which adds a mildly toxic
substance. The venom is subsequently transported to the stinger apparatus, which is surrounded
by muscle fibers from the alkaline gland that create a sphincter-like structure. 14
Pathophysiology
Venom
Apidae
Honeybees and AHBs have very similar concentrations of the major components of their venom. The
difference usually lies in the amount of venom delivered to the victim and whether it is an isolated sting
or a mass envenomation.5
Melittin is the major component of honeybee
and AHB venom. It accounts for 50% of the venom’s
volume and is the major pain-inducing compound.
It is theorized that melittin causes neurotoxicity by
acting as a molecular mimic of an immunodominant
peptide which induces an acute disseminated encephalomyelitis. Melittin, with the aid of phospholipase A2 (PLA2), inserts itself into the phospholipid
layer of cell membranes, induces skeletal muscle
necrosis, disrupts the vascular endothelium, and
causes the breakdown of red blood cells, leukocytes,
and platelets. Other venom components include the
major allergen PLA2, hyaluronidase, and mast-cell
degranulating protein.5, 6, 9, 15-17
Hyaluronidase is a secondary allergen known
as a “spreading factor” because it causes the breakdown of connective tissue and increases the uptake
and spread of melittin and PLA2. Hyaluronidase
makes up about 1%-2% of honeybee venom. Hy-
aluronidase is also present in the venom of other
animal species, including spiders and snakes, where
it serves a similar function. 6, 9, 18, 19
Apamin, another bee venom peptide, is a
neurotoxin that primarily affects the spinal cord.
Adolapin is a recently-described bee venom peptide and has anti-inflammatory effects. Adolapin
may explain why apitherapy seems to be effective
in treating some forms of arthritis.3, 20
Mast-cell degranulation protein makes up about
2% of honeybee venom and causes mast cells to
break down, releasing histamine. Honeybee venom
itself also contains small amounts of histamine. The
exogenous and endogenous histamine contribute
to localized inflammation and increased venom
absorption.6, 8
Bumblebee (B. terristris) venom also contains the
major allergen PLA2, proteases, and hyaluronidase.
Bumblebee venom is chemically and antigenically
related to honeybee venom and can have significant
immunologic cross-reactivity. 10, 11
Vespidae
Vespidae venom has similar protein compositions across
different species and contains hyaluronidase and
phospholipase. However, there are a few differences
between Vespidae and Apidae venom that should be
noted. For example, the intense pain that is caused by
hornet and wasp stings is largely due to serotonin and
acetylcholine, which make up 1%-5% of dry venom
weight. Wasp kinins (venom peptides) contribute
to pain production and can also produce significant
hypotensive effects. Vespula venom also contains Antigen 5, which may function as a major allergen.3, 21
Allergic Reactions And Anaphylaxis
Bee and wasp venoms contain 9-13 different
peptide antigens that all may trigger allergic reactions. The most well known allergic reaction is the
Type I anaphylactic or immediate hypersensitivity reaction (Table 1). This reaction is mediated by
immunoglobulin E antibodies, which trigger mast
cell degranulation when they are cross-linked by
the appropriate antigen. Symptoms usually occur
distant to the sting site and include hives, pruritis,
Table 1. Types Of Hypersensitivity Reactions
Type
Definition
Examples
Type I
Anaphylactic or immediate hypersensitivity
Allergic asthma, allergic conjunctivitis, anaphylaxis, angioedema, atopic
dermatitis
Type II
Antibody dependent
Autoimmune hemolytic anemia, immune thrombocytopenia, transfusion
reactions, rheumatic fever
Type III
Immune complex
Rheumatoid arthritis, serum sickness, systemic lupus erythematosus,
immune complex glomerulonephritis
Type IV
Cell mediated (delayed type hypersensitivity)
Contact dermatitis, temporal arteritis, celiac disease, transplant rejection
Pediatric Emergency Medicine Practice © 2008
June 2008 • EBMedicine.net
dyspnea, hypotension, loss of consciousness, and
heart palpitations (Table 2). Symptoms may start
within 15 minutes after exposure but can be delayed for as long as 6 hours. It is important to note
that upper airway obstruction is the leading cause
of death, and intractable hypotension is the second
leading cause of death in patients with anaphylaxis.
Such patients require intensive supportive care including airway control and restoration of hemodynamic stability with aggressive fluid resuscitation
and pressor support.22 Nearly all deaths caused by
Hymenoptera envenomation occur by Type I immediate hypersensitivity. 22, 23
Other immune-mediated reactions to Hymenoptera envenomation include immune complex (Type
III) and cell-mediated (Type IV) reactions. Type III
(serum sickness) reactions occur 3-14 days after the
sting and present with fever, headache, urticaria,
lymphadenopathy, polyarthritis, and polyarthralgias. Type II hypersensitivy reactions (antibody
mediated) do not commonly occur following Hymenoptera envenomation.24, 25
Major local reactions are usually the result of a
Type IV hypersensitivity reaction. The associated
local edema and erythema can last up to a week.22
Mass Stinging Events
Table 2. Clinical Presentation
Of Hymenoptera Envenomation
(Hypersensitivity Reactions)
Table 3. Clinical Presentation Of Mass
(Toxic) Envenomation
System
Symptoms
Systems
Symptoms
Prodromal
Pruritis
Metallic taste
Feeling of impending doom
Neurologic
Coma
Vital Signs
Vital Signs
Tachycardia
Tachypnea
Hypotension
Hypoxia
Tachycardia
Tachypnea
Hypotension
Hypoxia
Dermatologic
Pain
Erythema
Edema
Respiratory
Acute respiratory distress syndrome
Cardiovascular
Sinus tachycardia
Syncope
Tachydysrhythmias
Myocardial necrosis
Abdominal
Nausea
Vomiting
Hepatic failure
Renal failure
Hematologic
Hemolytic anemia
Thrombocytopenia
Disseminated intravascular coagulopathy
Metabolic
Metabolic acidosis
Musculoskeletal
Rhabdomyolysis
Dermatologic
Respiratory
Mass stinging events can be acutely life-threatening
due to the toxic action of large amounts of injected
venom. Toxicity from massive honey bee envenomation occurs directly from the systemic effects of the
venom, as opposed to immune-mediated anaphylaxis (Table 3). Death may result from exposure to
hundreds or thousands of stings. 6, 8, 23
Mass envenomations usually occur when stinging
insects respond to an intruder as a threat to their colony. Most mass envenomation cases that are reported in
the literature involve hundreds of stings and can result
in toxic systemic reactions and renal failure.6, 8, 9, 26
Mass bee envenomations usually number in the
hundreds to thousands of stings while mass wasp
envenomations usually involve tens to hundreds,
reflecting hive size. Stings are predominately in the
head and neck because the insects prefer to sting in
these areas, but stings can also involve other exposed areas such as the arms and legs.6
The very young and the very old may be at
greater risk for morbidity and mortality from
massive bee attacks. Children have smaller body
mass and are exposed to a greater amount of
venom per kilogram. However, the few docu-
Flushing
Warmth
Urticaria
Edema
Wheezing, bronchospasm
Bronchorrhea
Cough
Laryngeal edema
Angioedema of the tongue, upper airway
Cardiovascular
Syncope
Tachydysrhythmias
ECG changes: ST and T wave
Abdominal
Nausea
Vomiting
Diarrhea
Bloating
Crampy pain
Adapted from Ford and Delaney “Clinical Toxicology” Chapter 114
Hymenoptera
Adapted from Ford and Delaney “Clinical Toxicology” Chapter 114
Hymenoptera
EBMedicine.net • June 2008
Pediatric Emergency Medicine Practice © 2008
mented cases of more than 1000 honeybee stings
in children have resulted in recovery after hospitalization. Children are more likely to be stung
due to carelessness and are less able to escape
when stung.6, 27-29 The elderly often have co-morbidities that increase their risk of severe outcome
after mass envenomation.
The initial symptoms after massive envenomation include edema, fatigue, fever, nausea, vomiting, localized pain, and loss of consciousness. Rapid
onset of diarrhea and urinary incontinence may be
secondary to endogenous histamine release. Stings
to the eyes can lead to corneal edema and ulceration.
If bees are swallowed and internal envenomation
occurs, life-threatening pharyngeal edema and
respiratory obstruction may result. Systemic toxicity usually develops within 24 hours. Multisystem
derangements include hemolysis, rhabdomyolysis,
transaminitis, thrombocytopenia, and disseminated
intravascular coagulation. Rhabdomyolysis may
lead to oliguria, acute tubular necrosis, and renal
failure. With excellent supportive care, the systemic
toxicity is usually reversible. No specific antidotes
are available. 8, 22, 23, 26, 30
Death from mass envenomation has been
reported in victims with 500-1000 stings. With aggressive supportive care, survival is possible in such
situations.8
physical examination typically confirms the history. However, it may be impossible to obtain a
history if the patient is nonverbal, such as a very
young child, or if the patient presents in extremis.
In cases where the etiology is not clear, the differential diagnosis should be expanded to include other
considerations.
For example, local reactions may be mistaken for
other envenomations or localized infections, such as
abscess or cellulitis. In patients with anaphylaxis,
allergic reactions to other allergens, such as foods or
medications, should be considered. Causes of acute
shock must be considered and differentiated. Physical findings such as warm, flushed skin can help
differentiate between anaphylactic shock and other
types of shock. Systemic mastocytosis and urticaria
pigmentosa should also be considered because the
mast cell degranulation in these patients may mimic
anaphylaxis. Scombroid poisoning may also present
in a similar fashion.36
Although toxic systemic reactions from mass
envenomations are usually not difficult to diagnose
with the presence of multiple sting marks on the
skin, other causes of progressive multi-organ failure,
such as sepsis, should be considered.
Urticaria Pigmentosa And Mastocytosis
Patients with urticaria pigmentosa have focal salmon-colored to brown macules that produce a whealand-flare reaction when stroked. Biopsy of these
lesions shows abnormally high numbers of mast
cells. Patients can have acute episodes of mast cell
degranulation that are clinically indistinguishable
from allergic anaphylaxis. There have been reports
of these patients having equivocal bee venom-specific IgE and still exhibiting full anaphylactic responses
and mastocytosis.36, 63-65
Other Reactions
In general, most Apidae envenomations are characterized by transient local reactions of erythema,
edema, and pain, but other unusual manifestations
have been known to occur. Vasculitis, neuritis, and
encephalitis have been reported several days to
weeks after a bee sting. Thrombotic thrombocytopenic purpura has also been reported as a rare complication of bee stings.17, 31, 32
Oropharyngeal stings can cause significant
edema resulting in airway obstruction. The airway
obstruction usually occurs early in presentation but
may be somewhat delayed. These patients warrant
close monitoring and may require aggressive airway
management.22, 33, 34
Allergy to honeybee body components has
also been documented. Patients have reportedly
developed inhalant allergy to whole bee body components, though the exact body component has not
been identified. These patients usually also have a
concurrent bee venom sensitivity and develop the
allergy through occupational exposure.35
Prehospital Care
Prehospital care of the patient with bee or wasp
envenomation consists of excellent supportive
care and transport to the nearest emergency
department. The patient with anaphylaxis and
respiratory distress must be treated rapidly and
aggressively. The patency of the airway should be
maintained while supplemental oxygen is provided. Nebulized albuterol may be considered
for treatment of bronchospasm. Bag-valve-mask
ventilation or endotracheal intubation may be
required for severe respiratory compromise. Subcutaneous or intramuscular epinephrine should be
administered quickly and intravenous access established. Intravenous doses of diphenhydramine
and corticosteroids are also beneficial. Hypotension is treated with intravenous boluses of normal
saline and pressors as needed.
Differential Diagnosis
In most cases, patients seeking medical attention
are able to provide the specific history of being
stung by a bee, wasp, or unidentified insect. The
Pediatric Emergency Medicine Practice © 2008
June 2008 • EBMedicine.net
ED Evaluation
arterial blood gas analysis may be helpful in evaluating the patient with respiratory distress or hemodynamic compromise. Later, after the patient has been
referred to an allergy-immunology specialist, further
testing to determine the specific allergen may be
undertaken as outlined later in this article.
As with all patients presenting to the emergency
department, the initial evaluation of patients with bee
or wasp envenomation consists of rapid identification
and stabilization of any immediate life-threatening
problems. This is followed by a more comprehensive
history, physical examination, and diagnostic evaluation. After airway, breathing, and circulation have
been evaluated and stabilized, a detailed history
should be obtained for the following information:
past medical history, medications, immunization
status, and allergies (with special attention to prior
history of bee or wasp exposure and reactions, since
patients who have been previously sensitized to bee
or wasp stings have a 30%-60% chance of developing
anaphylaxis with future stings). It is also important
to note the estimated number of stings, progression of
symptoms since envenomation, and types of prehospital therapies performed. Tetanus status should be
updated, if appropriate.
Venom Allergy
A detailed history of the patient’s allergic reaction is
essential in diagnosing venom allergies, including
the specific insect involved, the symptoms experienced, and the sequence and timing of events.
Accurate diagnosis is important due to its implications for management. Tests for venom-specific IgE
antibodies can also be performed and are essential
if desensitization is being considered as a treatment.
Skin testing by an allergist should be performed
with venom extracts rather than whole body extracts. Whole body extracts are less sensitive in
diagnosing venom allergy.35,37-40
Treatment
Diagnostic Studies
Treatment of Aspidae and Vespidae envenomation
depends on the severity of the clinical presentation
as well as the type of reaction involved. See Table 4
for more information.
In the emergency department, the diagnosis of bee
or wasp envenomation is clinically made after historical and physical examination data are evaluated.
Although specific diagnostic testing for Hymenoptera
envenomation is not available in the acute setting,
other laboratory evaluations may be warranted,
depending on the patient’s condition. For example,
Stinger Removal
Conventional wisdom states that the stinger should
be removed via scraping with a knife, credit card, or
Table 4. Classification And Treatment Of Reactions To Hymenoptera Envenomations
Reaction
Clinical Presentation
Treatment
Local (allergic and toxic)
Localized pain, pruritis, edema, erythema,
warmth
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Solenopsis (imported fire ants) envenomation
characteristically
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results in pustule formation
Cold compresses, analgesics, oral antihistamines, large local
reactions may benefit from oral steroids
Mild
Generalized flushing, pruritis, urticaria
Oral antihistamines, steroids
Moderate
Generalized weakness, chest and throat tightness,
nausea,
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vomiting, diarrhea, generalized
angioedema
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IV antihistamines, steroids, subcutaneous epinephrine
Severe
Wheezing, stridor, laryngeal and pulmonary edema, IV antihistamines, steroids and IM or IV epinephrine, IV
hoarseness,
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dyspnea, cyanosis, tachycardia,
crystalloid,
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vasopressors, inhaled beta agonists, inhaled
hypotension,
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cardiovascular collapse, confusion,
racemic
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epinephrine for stridor
coma
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Systemic toxic
(mass envenomations)
Vomiting, diarrhea, generalized edema, collapse,
coma,
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confusion, headache, muscle spasms,
seizures,
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tachycardia, hypotension, hemolysis,
thrombocytopenia,
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disseminated intravascular
coagulation,
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rhabdomyolysis, acute renal failure,
hepatotoxicity
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Delayed allergic
(serum sickness)
Fever, malaise, urticaria or other rashes,
Oral analgesics, antihistamines, steroids
lymphadenopathy,
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myalgia, arthralgia, polyarteritis,
headache,
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glomerulonephritis, nephrotic syndrome,
necrotizing
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vasculitis
Systemic Allergic Reaction
EBMedicine.net • June 2008
Supportive care (i.e., correcting hypotension, coagulopathy,
renal dysfunction, etc.); no specific antidote or allergy
treatment
Pediatric Emergency Medicine Practice © 2008
fingernail rather than being plucked or pinched out.
It was reasoned that plucking or pinching the venom
sac would cause injection of additional venom.2
In vivo studies have shown that nearly all the
venom is injected into the victim within the first few
seconds after the sting. By the time the patient presents for care, stinger removal by pinching the stinger
does not increase the degree of envenomation.12, 13
Delays in stinger removal cause more venom
to enter the wound as opposed to inappropriate
removal technique. Visscher et al used sting wheal
bioassays to reflect the quantity of venom received
and reported an increase in wheal size with increased time between sting delivery and removal.
Therefore, it may be prudent to remove the stinger
by the quickest technique available in order to stop
further venom exposure.13, 41, 42
Local Reactions
Aspidae and Vespidae envenomation typically results
in localized pain and erythema that resolve in a few
hours. Cold compresses and analgesics are usually
all that are needed.1
Large local reactions may require the addition
of antihistamines and corticosteroids to manage
symptoms. Antihistamines, such as diphenhydramine, can be given by mouth or via IV depending
on the severity of the reaction. Diphenhydramine
1 mg/kg IV up to 50 mg or hydroxyzine 0.5 mg/kg
PO up to 50 mg are both suitable H1 antihistamines.
Hydroxyzine should not be given intravenously. H2
blockers can also be administered and have been
found to be just as efficacious as H1 blockers in urticaria and anaphylaxis. H2 blockers should be given
when hypotension is prominent and if sedation and
anticholinergic side effects are not desirable. The
combination of H1 and H2 blockers appears to be
superior to either agent alone and should be given in
severe anaphylaxis. Acute severe urticaria may also
benefit from a single dose of epinephrine, but this is
usually not necessary since there is no acute threat to
life. Adult dosages of famotidine 20 mg or ranitidine 50 mg IV can be used in situations of severe
anaphylaxis. Famotidine and ranitidine dosages
for children less than 12 years of age have not been
well established. In the future, the patient should be
instructed to take oral antihistamines as soon as possible if they are stung again to prevent the establishment of a local reaction.37
Systemic Reactions
The most common symptoms of bee and wasp envenomation are dermal in nature and include generalized
urticaria, flushing, and angioedema. The more severe
but less common anaphylactic reactions may cause
upper airway edema and circulatory collapse, ultimately resulting in death.1 Please refer to the “Special
Circumstances” section for more detailed managePediatric Emergency Medicine Practice © 2008
ment of upper airway obstruction due to anaphylaxis.
Epinephrine is the most rapid-acting and effective medication to reverse the life-threatening
complications of anaphylaxis and should be administered immediately for any patient with evidence of
an anaphylactic reaction. The intramuscular route
is preferable because it provides faster onset of action and more reliable blood levels than subcutaneous administration. The intravenous route should
be reserved for patients in extremis since it may be
associated with cardiac ischemia or dysrhythmias.
Epinephrine’s action on beta-adrenergic receptors
promotes the synthesis of cyclic AMP in mast cells,
thereby blocking further release of chemical mediators such as leukotrienes. The alpha-adrenergic
effects of epinephrine are of therapeutic benefit by
causing vasoconstriction with resultant improvement
in blood pressure and decreased swelling in edematous tissue. Delays in administration of epinephrine
may allow the airway obstruction or cardiovascular
collapse to progress to the point of irreversibility and
death.7 Patients should be treated with 0.01 mg/kg
(maximum dose 0.5 mg) of the 1:1000 dilution of epinephrine intramuscularly, preferably in the lateral
thigh. Epinephrine can be continued in a dose of 0.01
mg/kg IM at 20 minute intervals or an epinephrine
drip can be considered (0.05-1 µg/kg/min; titrate to
clinical effect).12
In cases of hypotension and cardiovascular
compromise associated with anaphylaxis, 1 or 2 IM
injections of epinephrine and rapid saline infusions
usually are efficacious. H2 blockers seem to have a
positive effect on hypotension as well. If the patient
is refractory to these modalities, then IV epinephrine
should be initiated. Fortunately, most patients with
anaphylaxis will not require such intensive therapy
and will respond well to 1 or 2 doses of epinephrine
given intramuscularly at 15-20 minute intervals,
along with IV fluid resuscitation.12
Corticosteroids are recommended for all anaphylactic patients. Though corticosteroids have no
immediate benefit, they are thought to speed the
resolution of angioedema and urticaria. Corticosteroids block the formation of late phase reactants.
It is theorized that corticosteroids may prevent
recurrence of symptoms after the initial treatment
of anaphylaxis. Dosages similar to status asthmaticus should be initiated for anaphylaxis, such as
methylprednisolone 2 mg/kg IV bolus followed
by 1 mg/kg every 6-8 hours. In milder cases, oral
corticosteroids such as prednisolone or prednisone
can be dosed at 1 mg/kg twice a day. 7, 2, 12
Prevention
Prevention of Apidae stings is especially important in
patients with an allergy to bees. Avoidance of bright
clothing, flowers, scented deodorants, shampoos, and
June 2008 • EBMedicine.net
perfumes helps to decrease attraction of these insects.
Also, patients with known allergy to bees should
wear long sleeves, shoes, and long pants when out of
doors to further avoid being stung.2
This allows for close approximation of colonies
with the possibility of having more than 500 fire ant
mounds per acre in some areas. Each colony can
have up to half of a million individual insects.43, 46
The 2005 annual report of the American Association of Poison Control Centers documented 2101
exposures to ant species. Approximately 1100 of
these exposures were in children less than 19 years
of age with over 250 exposures treated at a health
care facility and no deaths reported.4 Unfortunately, significant under-reporting occurs, making
it difficult to estimate the true number of fire ant
exposures.
In 1989, Stafford et al published the results of
a survey conducted with the cooperation of the
American Academy of Allergy and Immunology
Fire Ant Subcommittee. They reported that over
20,750 patients are treated annually for significant reactions to fire ants in the southeastern
United States. Of these patients, an estimated
63% experienced local reactions only, while 2%
required medical intervention for life-threatening
anaphylaxis.53
Part II. Formicidae (Ants)
Epidemiology
The ant of greatest medical importance in the United
States is the imported red fire ant (Solenopsis invicta)
which belongs to the subfamily Myrmicinae and family Formicidae. The fire ant’s painful sting accounts
for its name. In addition, the venom is more likely
to produce hypersensitivity reactions than that of
native North American ant species. The fire ant was
introduced from South America to Alabama in the
1930s via shipments of infested nursery stock and
other agricultural products and has since spread
to the southern United States. It now ranges from
southeastern Virginia to central Texas and Oklahoma, where it has largely displaced and eliminated
native ant species. S. invicta has been reported to
infest more than 310 million acres in 12 states and
Puerto Rico. Other states at risk of being colonized
with imported fire ants include: Arizona, California,
New Mexico, Oregon, and Washington. There are
other species of fire ants found in North and Central
America as well as the Caribbean and Pacific islands.
Allergic reactions to the venom of all of these species
have been reported. Solenopsis richteri, the black
imported fire ant, is found in areas of northeastern
Mississippi and parts of Alabama.3, 36, 43-46
Fire ants measure 2-5 mm in length. They are
reddish-brown to black, highly mobile, and very aggressive. They have powerful mandibles as well as a
stinger at the end of the abdomen. Stings occur most
frequently during the summer months. However,
encounters with humans may occur at other times if
the fire ants are actively seeking new sites for colony
survival during periods of environmental stress.3, 43, 47
In endemic areas, 23%-58% of the population
will experience a fire ant bite or sting in the course
of a year. It has been estimated that approximately
24%-28% of the population in these endemic areas
has hypersensitivity to fire ant venom via skin testing. Children younger than 15 years of age are the
most likely to be stung.48, 49
Problems arise when fire ants come in direct
contact with humans. In urban areas, fire ants build
mounds in open areas such as playgrounds and
lawns. They also can build colonies underneath
pavement and buildings. In rural areas, fire ants are
a hazard to humans and farm animals and can also
damage farm equipment, electrical systems, irrigation systems, and crops.43, 47, 49-52
Fire ant colonies differ from bee and wasp colonies in that they have multiple queens in one colony.
EBMedicine.net • June 2008
Etiology
Stinging Mechanism
Fire ants attack when their colony is threatened, and
the ants appear to boil out of the dome-shaped nest
to attack in huge numbers. Multiple stings are the
rule rather than the exception. The ant uses its mandibles to attach itself to the victim’s skin and arches
its back to inject venom through the stinger located
at the end of its abdomen. Venom is released from
the venom sac and injected over seconds to minutes
through the stinger, which is usually 0.5-1 mm in
length. The volume of the venom sac is approximately 40 nanoliters and the volume of venom delivered in a single sting has been estimated at 0.04-0.11
microliters. If not removed quickly, the ant will sting
repeatedly by using its head as a pivot, withdrawing
the stinger and reinserting it in multiple sites within
one area.43, 46, 52, 54
Pathophysiology
Venom
Fire ant venom differs from that of other Hymenoptera due to its mostly water-insoluble alkaloid composition. Piperidine alkaloid accounts for 95% of
the venom’s volume and causes histamine release as
well as necrosis of human skin. The alkaloids do not
result in IgE-mediated responses but have cytotoxic,
hemotoxic, bactericidal, and insecticidal properties
and also activate the complement pathway. Piperidines are responsible for the pain and other typical
findings of fire ant stings.52, 54-56
Pediatric Emergency Medicine Practice © 2008
Clinical Pathway For Hymenoptera Sting Management
Patient with Hymenoptera
envenomation
Local or anaphylatic
reaction?
Local
reaction
Monitor 4-6
hours for large local
reaction.
Symptom
improvement?
Consider PO
antihistamines and
corticosteroids.
(Class II)
Yes
Patient cleared for
discharge home on
antihistamines and
corticosteroids.
Anaphylactic
Reaction
Life-threatening
episode?
Yes
NO
NO
Consider IM epinephrine;
PO, IM, or IV antihistamines; and corticosteriods.
(Class II)
Initiate IM epinephrine
(consider IV if in extremis),
antihistamines, and corticosteroids. Consider inhaled
alpha- and beta-agonists,
airway management,
and IV fluids.
(Class II)
NO
Good clinical
response?
Admit and monitor for
late phase reactants or
delayed hypersensitivity.
Admit patients with severe
reactions to ICU.
Yes
Once symptoms
resolve, discharge home
on PO antihistamines,
corticosteroids, and Epi-Pen©.
(Class II)
Patient should consult
with an allergist.
The evidence for recommendations is graded using the following scale. For complete definitions, see back page. Class I: Definitely recommended. Definitive,
excellent evidence provides support. Class II: Acceptable and useful. Good evidence provides support. Class III: May be acceptable, possibly useful. Fair-togood evidence provides support. Indeterminate: Continuing area of research.
This clinical pathway is intended to supplement, rather than substitute for, professional judgment and may be changed depending upon a patient’s individual
needs. Failure to comply with this pathway does not represent a breach of the standard of care.
Copyright © 2008 EB Practice, LLC. 1-800-249-5770. No part of this publication may be reproduced in any format without written consent of EB Practice, LLC.
Pediatric Emergency Medicine Practice © 2008
10
June 2008 • EBMedicine.net
Differential Diagnosis
The proteins in fire ant venom are highly allergenic but only make up 0.1% of the dry weight
of the venom. To date, 4 protein allergens have
been isolated: Sol i 1, Sol i 2, Sol i 3, and Sol i 4. All
of these proteins have been shown to be important
allergens. Patients have been found who react to
every combination of these 4 proteins. These 4
allergens appear immunologically distinct when
tested with human IgE antibodies. Sol i 1 is a
venom phospholipase that exhibits immunologic
cross-reactivity with vespid venom phospholipase. This is important because patients who are
sensitized to vespid venom can present with significant allergic reactions after fire ant stings. Sol
i 1 comprises 2%-5% of the venom protein. Sol i 2,
3, and 4 are not immunologically related to apid
or vespid venom proteins. Sol i 2 accounts for
two-thirds of the venom protein and has strong
phospholipase A activity. Sol i 3 comprises 20%
of fire ant venom protein and is a member of the
antigen 5 family of venom proteins but does not
exhibit immunologic cross-reactivity with vespid antigen 5. Sol i 4 accounts for 8%-10% of the
venom protein and is related to but not immunologically cross-reactive with Sol i 2. Hyaluronidase
is also present in fire ant venom.43, 50, 52, 55-58
In most cases, patients or their caretakers are able to
provide the history of being stung by fire ants. The
characteristic formation of pustules within 24 hours
typically confirms the clinical suspicion of fire ant
envenomation. However, when the etiology is not
clear, the differential diagnosis may include other
considerations such as localized pustular infections
or cellulitis due to Staphylococcal or Streptococcal
bacteria. In the case of systemic reactions, including
anaphylaxis, exposure to other allergens should be
considered. A detailed history of recent foods, medications, and other exposures may reveal another
etiology for the patient’s illness.
Prehospital Care
The prehospital care provider who is called to
transport an individual with fire ant envenomation
should make a rapid assessment of whether the
patient is experiencing limited local effects or a
life-threatening systemic reaction. The patient with
respiratory distress, cardiovascular compromise,
and anaphylaxis must be treated aggressively and
transported rapidly to the nearest emergency department for further stabilization. In this situation,
it must be recognized that early administration
of subcutaneous or intramuscular epinephrine is
essential to reverse the systemic effects of anaphylaxis, including upper and lower airway obstruction. Supplemental oxygen should be provided
to all patients with respiratory distress, and nebu-
Mass Stinging Events
Recently, mass sting attacks by fire ants have been
reported in young children and infants as well
as elderly residents of nursing homes. It is clear
that immobilized individuals are at risk for mass
envenomation when they encounter fire ants.43, 59
Cost-Effective Strategies
1. Prescribe antibiotics for Hymenoptera envenomation only when secondary bacterial infection occurs.
The immediate local swelling, erythema,
warmth, and pain are due to venom effects or
allergic reactions and should not be mistaken
for infection. Empiric antibiotic prophylaxis is
generally not indicated. Secondary bacterial
infections typically develop more than 24 hours
after envenomation and should be treated if
increasing inflammation, lymphangitis, fever, or
leukocytosis develops.
lactic reactions that respond readily to treatment
and remain asymptomatic after 4-6 hours of
observation. However, it is important to instruct
the patient to return immediately if hoarseness,
wheezing, dyspnea, dizziness, or worsening
swelling occur.
3. Not all patients with a hypersensitivity reaction to Hymenoptera envenomation require a
referral to an allergist.
Patients with only mild local reactions are at
minimal risk for anaphylaxis with subsequent
stings and do not require referral to an allergist.
However, patients with severe local reactions or
systemic reactions (i.e., anaphylaxis) should be
referred for further evaluation, education, and
consideration for venom desensitization immunotherapy.
2. Not all Hymenoptera envenomation require
hospital admission.
Patients who may be safely discharged home
from the ED include those with limited local
reactions as well as patients with mild anaphyEBMedicine.net • June 2008
11
Pediatric Emergency Medicine Practice © 2008
lized albuterol may be considered for treatment of
bronchospasm. Bag-valve-mask ventilation may be
required for severe respiratory compromise, while
endotracheal intubation should be considered as
a last resort due to anticipated difficulties with
intubation secondary to upper airway obstruction.
Establishment of intravenous access will allow
administration of crystalloid fluids as well as pressors, diphenhydramine, corticosteroids, and other
medications as needed.52
wheal-and-flare reaction evolves, which then turns
into a pustule over the next 20-40 minutes. The
pustular fluid initially contains lymphocytes and
other leukocytes, but after 24-48 hours it mostly contains necrotic debris. Local reactions can be treated
symptomatically, with analgesics and local measures
such as cool compresses and frequent cleanings, to
prevent secondary bacterial infection.47, 52
Large Local
Large local reactions initially present very similarly to local reactions except that they evolve into
pruritic erythema and induration, which expands
for the next 24 hours. This reaction may expand to
involve an entire extremity before they subside after
48 hours. Typical pustules develop at the sting site,
much like the local reaction, except that the fluid
contains mostly eosinophils.52
ED Evaluation
The first priority is to quickly identify and treat any
life-threatening effects that develop following fire
ant envenomation. After the initial stabilization,
a more comprehensive physical examination and
diagnostic evaluation may be completed. A detailed
history should be obtained including past medical
history, medications, tetanus immunization status,
and allergies (with special attention to prior history of Hymenoptera exposures and reactions). It is
also important to note estimated number of stings,
progression of symptoms since envenomation, and
types of prehospital therapies performed.
Systemic Allergic Reactions
In addition to local reactions, previously sensitized
patients may develop systemic allergic reactions in
response to fire ant envenomation. As noted previously, people who are sensitized to wasp venom also
demonstrate immunologic cross-reactivity with fire
ant venom. Anaphylaxis is estimated to occur in
0.6%-6% of individuals who have been stung. The
clinical presentation and treatment of such anaphylactic reactions are the same as for anaphylaxis caused
by stings of other Hymenoptera.52
Diagnostic Studies
Local reactions typically do not necessitate diagnostic evaluation and should be treated symptomatically. However, in patients who have had systemic
allergic reactions to imported fire ant stings, a
thorough evaluation by an allergist is warranted.
The clinical history should be correlated with the
presence of fire ant specific IgE antibody by skin
testing or in vitro testing (i.e., Radioallergosorbent
test or RAST). Currently, only whole body extracts
are available on the market, as opposed to fire ant
venom extracts. Whole body extracts are manufactured by crushing and grinding whole fire ants. If
the patient demonstrates fire ant specific IgE antibodies upon testing, then venom immunotherapy
should be considered.52, 60, 61, 62
Systemic Venom Toxicity
Although rare, life-threatening systemic manifestations of direct venom toxicity have been reported
in victims of mass fire ant envenomation, and
infants, young children, and the immobile elderly
are at particular risk. These patients may develop
shock, metabolic acidosis, coma, hemolytic anemia,
coagulopathy, and multi-organ failure, requiring
aggressive supportive care. No specific antidotes are
available. Cardiorespiratory arrest and death have
also been reported.56
Prevention
Patients and their caretakers should be educated to
recognize and avoid fire ant mounds so that future
envenomation can be prevented. Shoes and protective clothing will also decrease the risk during outdoor activities. Young children must always be carefully supervised in areas where fire ants are known
to exist. Fire ant surveillance and eradication should
be undertaken near residences, daycare centers, and
nursing homes or any place where infants, elderly,
or other individuals with decreased ability to escape
from multiple envenomations reside.
Treatment
Reactions to the imported fire ant may be classified
into 4 categories: local, large local, systemic allergic,
and systemic venom toxicity. Treatment is dependent on the type of reaction.52, 56 See Table 4 for more
information.
Local
Local non-allergic reactions present with burning
pain at the sting site. Within 20 minutes, a pruritic
Pediatric Emergency Medicine Practice © 2008
12
June 2008 • EBMedicine.net
Risk Management Pitfalls For Bee, Wasp, And Ant Stings
6. “I thought that 24 hours of antihistamines and
corticosteroids would be enough for that allergic reaction.”
A 3-day course of antihistamines and corticosteroids should be prescribed for all patients
who are discharged home after an episode of
anaphylaxis in order to suppress the recurrence of symptoms due to the ongoing release
of pharmacologically-active mediators of the
allergic response.
1. “I didn’t think a single bee sting could be fatal.”
In the setting of previous sensitization to
Hymenoptera venom, a single sting can result in fatal anaphylaxis. A patient who has
experienced Hymenoptera-induced anaphylaxis
incurs a 30%-60% risk for anaphylaxis with
subsequent stings.
2. “I should have used epinephrine earlier for
that patient with the anaphylactic reaction.”
Epinephrine should be administered immediately for patients with evidence of an anaphylactic reaction, upper airway obstruction,
or cardiovascular collapse. The intramuscular
route provides faster onset of action and more
reliable blood levels than subcutaneous administration, while the intravenous route should be
reserved for patients in extremis since it may be
associated with cardiac ischemia or dysrhythmias. Delays in administering epinephrine may
allow airway obstruction or cardiovascular collapse to progress to the point of irreversibility
and death.
7. “I didn’t think that patient would deteriorate
at home after discharge from the ER.”
Patients with life-threatening complications
of anaphylaxis (such as respiratory distress or
cardiovascular compromise) should be admitted to the hospital for observation and continued
therapy, even if the symptoms improve in the first
few hours of treatment. Patients with incomplete
response to therapy, debilitated patients, and
those with serious underlying cardiac or pulmonary illness should also be admitted. These
patients are at increased risk for deterioration at
home if discharged prematurely from the ER.
3. “I should have intubated that patient with upper airway obstruction sooner.”
If epinephrine and other immediate interventions fail to improve respiratory distress from
anaphylaxis-induced upper airway obstruction, early endotracheal intubation should be
strongly considered. A delay in airway control
may result in progressive angioedema, making it
impossible to intubate the patient and, therefore,
necessitating a surgical airway.
8. “I didn’t know that delayed reactions could occur over a week after envenomation.”
Patients may present 1-2 weeks after envenomation with serum sickness, which is a type III
hypersensitivity reaction mediated by immune
complex formation. This unusual presentation
is characterized by fever, arthralgia, myalgia,
rash, and adenopathy.
9. “I forgot to prescribe an EpiPen© when I discharged the patient.”
Patients who have experienced an episode of
anaphylaxis secondary to Hymenoptera envenomation should always be discharged home
with an EpiPen© (or other emergency epinephrine kit, such as Ana-Kit©). The risk of
anaphylaxis for such a patient is estimated to be
30%-60% if the patient is stung by Hymenoptera
in the future. It is important to educate patients
on the correct use of the epinephrine kit and the
importance of having it with them at all times.
4. “I wish I had checked the patient’s blood pressure sooner.”
Intractable hypotension is the second leading
cause of death in anaphylaxis after laryngeal
edema associated with upper airway obstruction. Early recognition is of key importance. Patients with such cardiovascular collapse require
early treatment with epinephrine, aggressive
volume resuscitation with intravenous crystalloid, and continuous infusions of vasopressors.
5. “I was so busy treating the other aspects of the
envenomation that I forgot to ask about tetanus immunization status.”
Although it is easy to focus on treating the more
impressive local and systemic reactions to these
envenomations, it is important not to forget the
basic principles of wound care, such as tetanus
prophylaxis.
EBMedicine.net • June 2008
10. “I didn’t know that I should have made a referral to an allergist.”
Patients who have experienced an episode of
anaphylaxis secondary to Hymenoptera envenomation should be referred to an allergist for
further evaluation and management including
education, skin-testing, and consideration for
venom desensitization immunotherapy.
13
Pediatric Emergency Medicine Practice © 2008
of apitherapy. Adolapin also appears to inhibit
the prostaglandin synthetase system and has
been shown to decrease edema and polyarthrtis
in rats.20, 66
Part III. Hymenoptera Points Of
Interest
Special Circumstances
Immunotherapy
Venom immunotherapy has been considered for
patients with severe systemic allergic reactions.
Venom immunotherapy has been shown to be
effective and safe for preventing sting-induced
anaphylaxis. It has been shown to be 97% effective in reducing anaphylaxis in adults with previous systemic reactions. It has been estimated that
without venom immunotherapy, 30%-60% of adults
with previous systemic allergic reactions will have
systemic reactions if stung again. Venom immunotherapy in general carries around a 10% risk of
inducing systemic allergic reactions and can potentially induce anaphylaxis. Fatalities are rare and are
estimated at 1 per year.1, 67-71
The indications for venom immunotherapy
are the following: history of anaphylaxis due to
Hymenoptera sting, cardiac or respiratory distress
after sting, evidence of venom-specific IgE, likelihood of continued exposure to stings, and good
likelihood of patient compliance. For example,
children with dermal reactions only after a Hymenoptera sting are not candidates for venom immunotherapy. It is not meant for patients who have
significant concurrent medical or immunological
disease, concurrent treatment with medications
(i.e., beta blockers) likely to impair possible treatment for anaphylaxis, and patients who are insufficiently willing or motivated to attend regularly
and complete the prescribed course of treatment.
Pregnant patients should not start immunotherapy
but can continue maintenance if already in treatment. Venom immunotherapy is contraindicated
for children less than 5 years of age and in patients with a history of chronic perennial asthma
and severe dermatitis.72-75
Patients who are considered for venom
therapy first undergo properly performed skin
testing with venoms from honeybees, wasps,
yellow jackets, yellow hornets, white-faced hornets, and paper wasps to diagnose Hymenoptera
sensitivity. Whole body extracts of S. invicta are
used for skin testing because S. invicta venom
extracts are currently unavailable on the market. If the patient demonstrates positive skin
tests, then immunotherapy is initiated. Venom
immunotherapy is given once or twice a week
for several months and patients should be premedicated with antihistamines to enhance the
effectiveness of immunotherapy. The therapy is
then spaced monthly or even longer for at least
3-5 years. When the skin test or in vitro tests for
specific IgE become negative, then therapy can
Upper Airway Management
Upper airway obstruction secondary to anaphylaxis
is a true medical, and possibly surgical, emergency.
If massive angioedema of the tongue or larynx is
present, then endotracheal intubation under direct
or fiberoptic laryngoscopy may be impossible. In
this situation, a surgical airway, such as a cricothyroidotomy, must be established to prevent a fatal
outcome. The first important point to make is that
of early recognition. When the gravity of impending upper airway obstruction is appreciated early,
emergency interventions are more likely to result in
a positive outcome. Endotracheal intubation may be
lifesaving when performed early, before the airway
obstruction becomes too severe. A second important
principle is full mobilization of available resources.
If your hospital has a rapidly available team to assist
with the difficult airway, it should be mobilized early. For example, some hospitals have a “STAT Difficult Airway Team” including an anesthesiologist
and an ENT surgeon, which can be paged to provide
rapid assistance in situations such as upper airway
obstruction. The emergency department’s difficult
airway cart should be brought to the patient’s bedside and the strategy for airway management as well
as contingency plans should be reviewed with available staff members. Aggressive medical management should be undertaken immediately and should
include intramuscular or intravenous epinephrine,
antihistamines, and corticosteroids. Inhaled alphaadrenergic agonists, such as epinephrine, can also be
administered via nebulization to decrease supraglottic and laryngeal edema. Heliox can also be considered as a temporizing measure since it decreases
airflow resistance and improves ventilation in upper
airway obstruction.12
Cutting Edge
Apitherapy
Apitherapy is the medical use of honey bee products including the honey, bee pollen, royal jelly,
and bee venom. The most highly visible application of apitherapy is bee venom therapy for autoimmune diseases and multiple sclerosis. Some
preliminary animal studies demonstrate positive
results in treating arthritis. However, further
studies are needed to confirm such findings in
humans. Adolapin, a bee venom peptide, has
been shown to have anti-inflammatory activity
and may be responsible for the beneficial effects
Pediatric Emergency Medicine Practice © 2008
14
June 2008 • EBMedicine.net
be discontinued. 40, 67, 73, 76, 77
Immunotherapy leads to marked changes in
cytokine secretion patterns by changing the abnormal T-helper 2 cell cytokine responses to a normal
T-helper 1 cell cytokine response. This leads to
a long-term loss of IgE synthesis and increase in
venom-specific IgG and a loss of the allergic
reaction.1, 37, 67
Though Apidae, Vespidae, and Formicidae contain
similar allergenic proteins, the current problem in
the clinical management of venom-allergic patients
is due to the existence of multiple reactivity in a
large fraction of patients. There does not seem to be
any significantly reliable method to determine the
primary insect which causes the patient’s sensitivity.
Therefore, manufacturers of venom immunotherapy
seras combine all of the important North American
insect species in each batch of extract. This appears
to be the most efficient course for the clinician to
treat venom-sensitive patients.57, 78, 79
lergic reactions may also require hospitalization. If
the symptoms improve after initial treatment in the
emergency department and do not recur during a
4-6 hour observation period, it is reasonable to discharge the patient home on oral antihistamines and
corticosteroids as well as a prescription for injectable
epinephrine and a referral for outpatient allergy-immunology evaluation. However, if moderate symptoms persist, such as throat discomfort, chest tightness, or vomiting, it is prudent to admit the patient
for continued observation. During hospitalization,
allergy-immunology consultation can be obtained.
In addition, the time in the hospital should be utilized for patient education and prevention of future
envenomations. Patients should be discharged
with a prescription for injectable epinephrine with
specific instructions of how and when to administer
the medication.80
The patient should also be instructed to use
antihistamines, such as diphenhydramine, as well
as to obtain a medic-alert bracelet, which can alert
emergency personnel to the presence of a sensitized
individual. Patient education is extremely important to achieve compliance because patients perceive
the injectable epinephrine as cumbersome or intimidating.37, 80
Disposition
Local Reactions
Patients with local reactions to Hymenoptera stings
can be discharged home from the emergency
department after symptomatic treatment. Rare
exceptions that require hospital admission would
include: large local reactions near the airway that
may cause respiratory compromise or large local
reactions of an extremity that may cause vascular
compromise. In addition to local wound care,
oral antihistamines and corticosteroids may be
prescribed for more significant local reactions. All
patients should be educated to avoid Hymenoptera
envenomation in the future.
Systemic Toxic (Mass) Envenomation
Patients with systemic toxic reactions secondary to mass envenomation should be admitted to
the hospital for close monitoring and supportive
care. Such patients with large numbers of stings
are at risk for multi-system toxicity, which may
occur on a delayed basis. Patients who have appeared stable in the emergency department have
subsequently decompensated with severe complications.
Mild Allergic Reactions
Summary
Patients who present with mild allergic reactions
to Hymenoptera envenomation are usually safely
discharged home from the emergency department
after a brief observation period. These patients
may have generalized urticaria, pruritis, or skin
flushing, but no respiratory distress or cardiovascular compromise. Their symptoms are typically
controlled with oral antihistamines, often with the
addition of oral corticosteroids.37 These patients
should be warned to try to avoid these stings in
the future.
Hymenoptera envenomation in the United States
results in significant morbidity and mortality every
year. The most common cause of severe or fatal
outcome is anaphylaxis. Less commonly, direct toxic
effects from mass envenomation may also result in
severe consequences. It is therefore necessary for the
emergency physician to be familiar with the clinical
presentation, as well as the appropriate evaluation
and management of these stings. Proper treatment
and patient education will optimize outcome for the
envenomation.
Moderate And Severe Allergic Reactions
All patients with severe allergic reactions that cause
respiratory distress or hemodynamic compromise
should be admitted to the hospital, often to an
intensive care setting. These anaphylactic reactions
require aggressive supportive care and vigilant
monitoring. Patients with moderate systemic alEBMedicine.net • June 2008
Case Conclusions
This 12-year-old boy sustained massive bee envenomation, likely the result of an aggressive swarm of
Africanized honeybees. You observed that he had several
15
Pediatric Emergency Medicine Practice © 2008
References
hundred bee stings to his face, extremities, and torso, but
no evidence of anaphylaxis. The immediate priorities of
airway, breathing, and circulation were attended to. He
was breathing comfortably without stridor, wheezes, or
hypoxia. He had moderate tachycardia but no hypotension. Intravenous access was obtained, and the patient
was treated with intravenous fluids, corticosteroids,
antihistamines, and analgesia. Although he remained
stable for several hours in the emergency department,
you admitted him for observation due to your concerns
that he may develop delayed toxicity secondary to the
massive envenomation. In the hospital, the patient did
indeed decompensate 12 hours after admission with
vomiting, tachycardia, hypotension, and altered mental
status. Laboratory evaluation revealed hemolysis, hemoglobinuria, rhabdomyolysis, renal insufficiency, and
hepatic transaminase enzyme elevations. Aggressive
supportive care measures in the intensive care unit were
required to stabilize the patient. His condition gradually
improved, and he was discharged home in good condition
after 1 week in the hospital.
You immediately recognized that this 7-year-old girl
was experiencing an anaphylactic reaction to the wasp
sting and brought her to the resuscitation room for aggressive management of this life-threatening emergency.
Oxygen and nebulized albuterol were administered,
and the patient was given an intramuscular injection
of epinephrine simultaneously. Intravenous access was
obtained, and the patient received fluids, antihistamines,
and corticosteroids. Her initial blood pressure was 72/40
mm Hg, and this improved to 90/64 mm Hg after 1 dose
of epinephrine and 2 boluses of normal saline. Her wheezing and oxygen requirement resolved, and her mental
status improved. She continued to have generalized urticaria, but the rash had faded considerably. You breathed
a sigh of relief as you consulted the allergy-immunologist
and made arrangements for hospital admission.
Your initial examination of the child revealed no
respiratory distress or other signs of anaphylaxis, and the
parents were not aware of the child having any prior exposure to fire ants. After confirming that the child had no
significant compromise of vital signs, you felt comfortable
that the child’s envenomation could be treated with good
wound management and symptomatic care. The affected
areas were gently cleansed with soap and water, and cool
compresses were applied. The child’s tetanus status was
confirmed to be current. The patient’s pain and itching
were treated with oral ibuprofen and diphenhydramine.
His irritability and tachycardia resolved as he stopped
crying and became more comfortable. Prior to discharge
home, you reassured the parents, who were thankful for
the good care their child received.
Pediatric Emergency Medicine Practice © 2008
Evidence-based medicine requires a critical appraisal of the literature based upon study methodology and number of subjects. Not all references are
equally robust. The findings of a large, prospective,
randomized, and blinded trial should carry more
weight than a case report.
To help the reader judge the strength of each
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as the type of study and the number of patients in the
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syndrome after bee sting. JAMA. 1979;242(20):2212-2213.
(Case report)
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LM. Diagnosis of allergy to stinging insects by skin
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Allergenic components of Solenopsis invicta (imported
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CME Questions
1) What is the most common cause of death following Hymenoptera envenomation?
a. Severe local tissue damage
b. Systemic toxicity following mass envenomation
c. Anaphylaxis
d. Delayed allergic reactions
2) What is the most important medication to
administer when treating a patient with severe
anaphylaxis?
a. Prednisone
b. Albuterol
c. Diphenhydramine
d. Epinephrine
3) What is the characteristic appearance of fire ant
stings?
a. Pustules
b. Urticaria
c. Macules
d. Purpura
18
June 2008 • EBMedicine.net
4) Which of the following Hymenoptera typically
can only sting once?
a. Fire ants
b. Honeybees
c. Wasps
d. Yellow jackets
11) Which of the following patients is the most
appropriate candidate for venom immunotherapy?
a. 3-year-old male with generalized urticaria after fire ant envenomation
b. 20-year-old healthy female college student with marked hand swelling, redness, and pain after a bee sting
c. 25-year-old healthy male landscaper with anaphylaxis to yellow jacket stings and a positive skin test for Hymenoptera sensitivity
d. 50-year-old homeless male with a history of chronic asthma who presents with wheezing after a bee sting
5) Which of the following Hymenoptera belongs
to the Family Apidae?
a. Wasps
b. Yellow jackets
c. Hornets
d. Bumblebees
6) Compared to normal domestic honeybees,
Africanized honeybees:
a. Are more venomous
b. Are more aggressive when the hive is threatened
c. Are more widespread in cold as well as warm climates
d. Are less likely to attack in large swarms
12) The name “Hymenoptera” means:
a. Honey producer
b. Painful stinger
c. Strong jawed
d. Membrane-winged
13) Which of the following therapies is contraindicated in the treatment of anaphylaxis with
respiratory distress?
a. Epinephrine
b. Beta-blockers
c. Corticosteroids
d. Antihistamines
7) What type of allergic reaction is anaphylaxis?
a. Type I, immediate hypersensitivity
b. Type II, antibody-dependent
c. Type III, immune complex
d. Type IV, cell-mediated
8) Imported fire ants:
a. Are not aggressive and usually do not sting when disturbed
b. Only sting once because their stinger is barbed
c. Have venomous stings but do not induce allergy
d. Often sting the victim multiple times
14) Imported fire ants:
a. Are more likely to cause hypersensitivity and anaphylaxis than native North American ant species
b. Are less aggressive than native North American ant species
c. Envenomate their victims via specialized poison glands in their mandibles
d. Build their nests in trees
9) Prevention of bee stings for sensitized individuals includes:
a. Wearing bright-colored clothing
b. Wearing strong perfumes
c. Wearing long-sleeved shirts and long pants while outdoors
d. Walking barefoot
15) Bumblebees:
a. Live in huge colonies containing many thousands of insects
b. Are often involved in mass stinging events
c. Account for a large majority of Hymenoptera stings
d. Are non-aggressive
10) The main cause of death from anaphylaxis is:
a. Upper airway obstruction secondary to laryngeal edema
b. Upper airway obstruction secondary to lip and tongue edema
c. Local airway obstruction secondary to bronchospasm
d. Refractory hypotension
EBMedicine.net • June 2008
16) Which of the following is the best method for
removing a bee stinger from the victim’s skin?
a. Pinching with tweezers
b. Grasping with fingers
c. Scraping with a credit card
d. Whichever method can be done the quickest
19
Pediatric Emergency Medicine Practice © 2008
Physician CME Information
Are you prepared to deal with the constantly
changing technologies of the 21st century?
Date of Original Release: June 1, 2008. Date of most recent review: May 10, 2008.
Termination date: June 1, 2011.
Accreditation: This activity has been planned and implemented in accordance
with the Essentials and Standards of the Accreditation Council for Continuing
Medical Education (ACCME) through the joint sponsorship of Mount Sinai School
of Medicine and Pediatric Emergency Medicine Practice. The Mount Sinai School
of Medicine is accredited by the ACCME to provide continuing medical education
for physicians.
Credit Designation: The Mount Sinai School of Medicine designates this
educational activity for a maximum of 48 AMA PRA Category 1 Credit(s)TM per
year. Physicians should only claim credit commensurate with the extent of their
participation in the activity.
ACEP Accreditation: Pediatric Emergency Medicine Practice is also approved by
the American College of Emergency Physicians for 48 hours of ACEP Category 1
credit per annual subscription.
AAP Accreditation: This continuing medical education activity has been reviewed
by the American Academy of Pediatrics and is acceptable for up to 44 AAP
credits. These credits can be applied toward the AAP CME/CPD Award available
to Fellows and Candidate Fellows of the American Academy of Pediatrics.
Needs Assessment: The need for this educational activity was determined by a
survey of medical staff, including the editorial board of this publication; review
of morbidity and mortality data from the CDC, AHA, NCHS, and ACEP; and
evaluation of prior activities for emergency physicians.
Target Audience: This enduring material is designed for emergency medicine
physicians, physician assistants, nurse practitioners, and residents.
Goals & Objectives: Upon completion of this article, you should be able to: (1)
demonstrate medical decision-making based on the strongest clinical evidence;
(2) cost-effectively diagnose and treat the most critical ED presentations; and (3)
describe the most common medicolegal pitfalls for each topic covered.
Discussion of Investigational Information: As part of the newsletter, faculty may
be presenting investigational information about pharmaceutical products that is
outside Food and Drug Administration approved labeling. Information presented
as part of this activity is intended solely as continuing medical education and is
not intended to promote off-label use of any pharmaceutical product. Disclosure
of Off- Label Usage: This issue of Pediatric Emergency Medicine Practice
discusses no off-label use of any pharmaceutical product.
Faculty Disclosure: It is the policy of Mount Sinai School of Medicine to ensure
objectivity, balance, independence, transparency, and scientific rigor in all
CME-sponsored educational activities. All faculty participating in the planning or
implementation of a sponsored activity are expected to disclose to the audience
any relevant financial relationships and to assist in resolving any conflict of
interest that may arise from the relationship. Presenters must also make a
meaningful disclosure to the audience of their discussions of unlabeled or
unapproved drugs or devices.
In compliance with all ACCME Essentials, Standards, and Guidelines, all faculty for
this CME activity were asked to complete a full disclosure statement. The information
received is as follows: Dr. Feng, Dr. Goto, Dr. Hutchinson, and Dr. Toscano report
no significant financial interest or other relationship with the manufacturer(s) of any
commercial product(s) discussed in this educational presentation.
Method of Participation:
Print Subscription Semester Program: Paid subscribers who read all CME
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June and December issues, and return it according to the published instructions
are eligible for up to 4 hours of CME credit for each issue. You must complete
both the post test and CME Evaluation Form to receive credit. Results will be kept
confidential. CME certificates will be delivered to each participant scoring higher
than 70%.
Online Single-Issue Program: Current, paid subscribers who read this Pediatric
Emergency Medicine Practice CME article and complete the online post-test
and CME Evaluation Form at EBMedicine.net are eligible for up to 4 hours of
Category 1 credit toward the AMA Physician’s Recognition Award (PRA). You
must complete both the post-test and CME Evaluation Form to receive credit.
Results will be kept confidential. CME certificates may be printed directly from the
website to each participant scoring higher than 70%.
Hardware/Software Requirements: You will need a Macintosh or PC with internet
capabilities to access the website. Adobe Reader is required to download
archived articles.
With “An Evidence-Based Approach To Techniques & Procedures,”
you will be.
Improve your skills with chapters on Emergency
Endotracheal Intubations, Procedural Sedation
In The ED, Noninvasive Airway Management
Techniques, and Emergency Imaging.
For more information or to order, call 1-800-249-5770 or click “Books & Manuals” on
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Coming In Future Issues:
Evaluation of the Pediatric Cervical Spine
Initial Assessment and Management of Knee, Ankle
and Wrist Injuries
GI Decontamination
Severe Brain Injury
Class Of Evidence Definitions
Each action in the clinical pathways section of Pediatric Emergency
Medicine Practice receives a score based on the following definitions.
Class I
• Always acceptable, safe
• Definitely useful
• Proven in both efficacy and effectiveness
Level of Evidence:
• One or more large prospective studies are present (with rare exceptions)
• High-quality meta-analyses
• Study results consistently positive
and compelling
Class II
• Safe, acceptable
• Probably useful
Level of Evidence:
• Generally higher levels of evidence
• Non-randomized or retrospective
studies: historic, cohort, or case
control studies
• Less robust RCTs
• Results consistently positive
Class III
• May be acceptable
• Possibly useful
• Considered optional or alternative
treatments
Level of Evidence:
• Generally lower or intermediate
levels of evidence
• Case series, animal studies, consensus panels
• Occasionally positive results
Indeterminate
• Continuing area of research
• No recommendations until further
research
Level of Evidence:
• Evidence not available
• Higher studies in progress
• Results inconsistent, contradictory
• Results not compelling
Significantly modified from: The
Emergency Cardiovascular Care
Committees of the American Heart Association and representatives from the
resuscitation councils of ILCOR: How
to Develop Evidence-Based Guidelines
for Emergency Cardiac Care: Quality of
Evidence and Classes of Recommendations; also: Anonymous. Guidelines
for cardiopulmonary resuscitation and
emergency cardiac care. Emergency
Cardiac Care Committee and
Subcommittees, American Heart Association. Part IX. Ensuring effectiveness
of community-wide emergency cardiac
care. JAMA. 1992;268(16):2289-2295.
Pediatric Emergency Medicine Practice is not affiliated with any pharmaceutical firm or medical device manufacturer.
CEO: Robert Williford President & Publisher: Stephanie Williford Associate Editor & CME Director: Jennifer Pai Director of Member Services: Liz Alvarez
Direct all editorial, subscription-related, customer service,
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Individual issues, including 4 CME credits: $30
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not intended to establish policy, procedure, or standard of care. Pediatric Emergency Medicine Practice is a trademark of EB Practice, LLC. Copyright © 2008 EB Practice, LLC. All rights reserved. No part of
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Pediatric Emergency Medicine Practice © 2008
20
June 2008 • EBMedicine.net