Download Primary Care Paramedic Diphenhydramine (Benadryl) Certification

Primary Care Paramedic
Diphenhydramine
(Benadryl)
Certification Package
Southwest Ontario Regional Base Hospital Program
London • Owen Sound • Windsor
1
Welcome to the Primary Care Paramedic Diphenhydramine Certification package! The addition of
Benadryl to your list of medications provides added opportunities for the treatment of symptomatic
allergic reactions and anaphylaxis.
This self-study learning package has been developed in order to help prepare you for this new skill.
It reviews the basics of the human immune system, the causes and effects of allergies and
anaphylaxis, and the treatment of these patients according to the BLS Patient Care Standards and
the Provincial Medical Directives. Additional information reviews the pharmacological properties of
epinephrine, diphenhydramine, and salbutamol.
Through personal study of this package, the BLS Standards section 2-14, and the Provincial
Medical Directives - Anaphylaxis/Allergic Reaction Protocol (along with any reference materials you
enjoy), the paramedic will be able to:
 Define allergic reaction, anaphylaxis, antigen, allergen, and antibody.
 List the common allergens most frequently associated with anaphylaxis.
 Describe the antigen-antibody response in an allergic reaction.
 Identify and differentiate between the signs and symptoms of allergic reaction and
anaphylaxis.
 Explain the various treatments and pharmacological interventions used in the management
of allergic reaction and anaphylaxis as per the BLS Patient Care Standards and the
Provincial Medical Directives.
 Describe how the pharmacological properties of epinephrine, diphenhydramine (Benadryl),
and salbutamol assist in the treatment of allergic reactions and anaphylaxis.
The attached Diphenhydramine Certification quiz, along with your own personal assessment,
serves as the evaluation of your learning. Once you have read the self-study package and
referenced materials, complete the quiz and submit it to the designated contact in your service.
The quiz will be forwarded to the Base Hospital for review.
Paramedics will be notified when they are certified to use Benadryl, and implementation of the new
treatment will be coordinated through your EMS service.
If you have any questions, feel free to contact us at the Southwest Ontario Regional Base Hospital
Program at any time.
Southwest Ontario Regional Base Hospital Program
London • Owen Sound • Windsor
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Introduction
An allergic reaction is an exaggerated immune system response to a foreign protein or other
substance. Anaphylaxis is an unusual or exaggerated allergic reaction (the most severe form),
requiring prompt recognition and specific treatment by the paramedic – a true life or death situation.
Approximately 1-2 percent of Canadians live with the risk of an anaphylactic reaction. Injected
penicillin and insect stings (especially fire ants, wasps, yellow jackets, hornets, and honeybees) are
the two most common causes of fatal anaphylaxis, although fewer than 5 persons die in Canada
each year from stings.
The Immune System
The immune system is a complex system responsible for combating infection in the body, with
components found in the blood, the bone marrow, and the lymphatic system. Once activated by an
invading substance (or pathogen), a complex cascade of events called the immune response
occurs in an attempt to destroy or inactivate the foreign substance.
The immune response involves two mechanisms – cellular immunity (a direct attack on foreign
substance by specialized cells), and humoral immunity (a chemical attack on the invading
substance).
The principal chemical agents of humoral immunity are called antibodies, or
immunoglobins (Igs).
When the body is exposed to an antigen (defined as any substance capable of inducing an immune
response), the humoral immune response causes a release of antibodies from cells of the immune
system. These antibodies attach themselves to the invading substance to assist in their removal
from the body. Common antigens include antibiotics and other drugs, foreign proteins, foods (nuts,
eggs, shrimp), allergen extracts (allergy shots), insect stings, hormones (insulin), blood products,
aspirin, NSAIDS, and X-ray contrast media.
Allergies
An individual’s first exposure to an antigen is called the primary response, or sensitization, resulting
in an immune response. Several days are required before both the cellular and humoral
components of the immune system respond. While generalized antibodies (IgG and IgM) are
released to help fight the antigen, other components of the immune system begin to develop
antibodies specific for the antigen.
If the body is exposed to the same antigen again, the immune system responds much faster, called
the secondary response. Antigen-specific antibodies are released, and are much more effective in
facilitating the removal of the offending antigen than are the generalized antibodies of a primary
response.
Some people become hypersensitive (allergic) to a particular antigen, having an unexpected and
exaggerated reaction. This allergic tendency is usually genetic, being passed from parent to child,
and is characterized by the presence of large quantities of IgE antibodies. An antigen that causes
the release of the IgE antibodies is referred to as an allergen.
Allergens can enter the body by oral ingestion, inhalation, topically (through the skin), and through
injection or envenomation (e.g. bee sting). When exposed to an allergen, IgE antibodies are
released and attach themselves to the membranes of basophils and mast cells – specialized cells
of the immune system that assist in the immune response. These cells release histamine and other
substances into the surrounding tissues.
Histamine is the principal chemical mediator of an allergic reaction. It is a potent substance that
causes bronchoconstriction, increased intestinal motility, peripheral vasodilation, and secretion of
gastric acids. Histamine also causes an increased vascular permeability, allowing leakage of fluid
from the circulatory system into the surrounding tissues. A common sign of a severe allergic
Southwest Ontario Regional Base Hospital Program
London • Owen Sound • Windsor
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reaction and anaphylaxis is angioedema – a marked edema of the skin involving the head, neck,
face, and upper airway.
The body’s use of histamine is a defensive mechanism, designed to minimize the body’s exposure
to the antigen. Bronchoconstriction decreases the possibility of the antigen entering through the
respiratory tract. Increased gastric acid production helps destroy an ingested antigen. Increased
motility moves the antigen quickly through the GI tract with minimal absorption of the antigen.
Vasodilation and capillary permeability help remove the antigen from the circulation where it has the
potential to do the most harm.
Anaphylaxis
Anaphylaxis usually occurs when an allergen is introduced directly into the circulatory system,
which is why it is more common following injections of drugs and diagnostic agents, and following
bee stings. The allergen is quickly distributed throughout the body, interacting with both basophils
and mast cells resulting in a massive dumping of histamine and other substances associated with
anaphylaxis.
The principal body systems affected by anaphylaxis are the cardiovascular system, the respiratory
system, the gastrointestinal system, and the integumentary system (skin).
Assessment Findings
Allergic reactions (hypersensitivity) range from a mild skin rash to a severe life-threatening
multisystem response, and can be delayed or immediate. Delayed hypersensitivity does not involve
antibodies, and may occur hours to days after exposure. It usually presents as a skin rash as a
result of exposure to certain drugs and chemicals (e.g. Poison ivy). Other signs/symptoms can
include mild bronchoconstriction, mild intestinal cramps, or diarrhea. The patient’s mental status
and vital signs will remain normal.
When most people use the term “allergy”, they are referring to immediate hypersensitivity, such as
hay fever, drug/food allergies, eczema and asthma. Immediate hypersensitivity does involve
antibodies in the immune response.
In anaphylaxis, symptoms normally begin within seconds of the exposure to an allergen, with only a
small percentage of cases taking over an hour to manifest. The severity of the reaction is often
related to the route of exposure and the speed of onset, with rapidly developing reactions tending to
be much more severe.
Respiratory symptoms include laryngeal edema and bronchoconstriction, resulting in difficult
breathing. Cardiovascular symptoms include tachycardia. The peripheral vasodilation and capillary
permeability result in profound hypotension. The cardiovascular collapse, aggravated by the
respiratory distress, results in a rapid deterioration of the patient’s mental status. Generalized
flushing and urticaria are common, as is the angioedema about the head, face, and neck.
Histamine effects on the GI system may result in nausea, vomiting, and diarrhea.
Southwest Ontario Regional Base Hospital Program
London • Owen Sound • Windsor
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Mild
Reaction
Gradual
Allergic Severe Allergic Reaction or
Anaphylaxis
Onset
Sudden, 30-60 seconds, but can be more than 1 hour
after exposure
Skin/vascular Mild flushing, rash, Severe flushing, rash, hives. Angioedema - swelling of
System
or hives
head, face, and neck. Tachycardia.
Respiration
Mild
Severe bronchoconstriction (wheezing), laryngospasm
bronchoconstriction
(stridor), difficulty breathing
GI System
Mild
cramps, Severe cramps, diarrhea, vomiting
diarrhea
Vitals
Normal to slightly Increased pulse early (may fall in late/severe case),
abnormal
increased respiratory rate early (falling late), falling
blood pressure
Mental
Normal
Anxiety, sense of impending doom, progressing to
Status
confusion and unconsciousness
Other – incident history of injected penicillin, insect
sting, or ingestion of known allergen.
Ominous sign – respiratory distress, signs of shock,
falling pulse, falling respirations, falling blood pressure
Management of Allergic Reactions/Anaphylaxis
First, ensure that the scene is safe to approach – the presence of chemicals or swarming bees can
pose a risk to paramedics. Do not overlook the possibility of coincidental trauma, as it is not
uncommon for people to fall or otherwise injure themselves as they try to escape from bees or
wasps. Signs and symptoms of trauma can be masked by those of anaphylaxis.
As per the BLS Standards, complete the primary survey, provide high-concentration oxygen, and
apply your cardiac monitor. Attempt to calm and reassure the agitated patient. Manage
airway/breathing problems (e.g. provide ventilatory support for hypoventilation/apnea, use
oral/nasal airways as required), and manage shock.
According to the Anaphylaxis/Allergic Reaction Protocol, patients with a confirmed or suspected
history of exposure to a probable allergen and experiencing signs and symptoms of a severe
anaphylactic reaction may receive both epinephrine 1:1,000 and diphenhydramine (Benadryl).
Patients demonstrating signs and symptoms of a moderate allergic reaction will receive only
diphenhydramine. In all cases, paramedics should evaluate the patient for additional use of
salbutamol, and if certified, IV access and fluid administration.
** review the complete Anaphylaxis/Allergic Reaction Protocol in the PCP Medical Directives.
Epinephrine (adrenalin) is a sympathomimetic, having both alpha and beta agonist actions. In
anaphylaxis, epinephrine is used to counter the effects of histamine on the body. Epinephrine
works on beta-receptors in the lungs to provide bronchodilation, while the alpha effects provide
vasoconstriction of arterioles. Epinephrine also limits the release of histamine and other chemicals
from basophils and mast cells, and reverses capillary permeability.
Epinephrine for severe anaphylaxis is given by SC/IM injection at a dose of 0.01 mg/kg (rounded to
nearest 0.05 mg) to a maximum dose of 0.3 mg. The paramedic may give a maximum of 2 doses
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London • Owen Sound • Windsor
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(see notes re patient under 10 kg, or patients with history of ischemic heart disease). See the
Directives for full details on epinephrine administration.
Benadryl is an antihistamine (blocks histamine receptor sites), and an anticholinergic. It reduces
the vasodilation, hypotension and tachycardia associated with histamine release by competing for
histamine receptor sites in the body. Benadryl’s onset of 15-30 minutes is not as fact acting as
epinephrine, but the duration of effects is longer at 3-12 hours.
Benadryl is administered by either IM injection or (where certified) by IV. Benadryl is not diluted for
IV administration, but should be administered slowly. Paramedics will give a maximum of 1 dose.
The provincial medical directive provides the following direction for dosing:
1. Administer Diphenhydramine for a moderate reaction or for a severe reaction after epinephrine
has been administered:
 <25kg = Required Patch
 25kg to 49kg = 25mg or 0.5ml
 ≥50kg = 50mg or 1.0ml
Salbutamol is Beta 2 specific sympathomimetic that dilates bronchial smooth muscle, thus
reversing the bronchoconstriction associated with allergic reactions/anaphylaxis. Benadryl itself
has no effect on the bronchoconstrictive action of some of the other substances released by
basophils and mast cells.
Thus, salbutamol remains a mainstay treatment when
bronchoconstriction is involved. See the SOB/Respiratory Distress Protocol.
Severe allergies and anaphylaxis can progress rapidly and result in death in minutes. The release
of histamine and other substances following exposure to an allergen causes bronchospasm, airway
edema, peripheral vasodilation, and increased capillary permeability, resulting in compromise to
both the respiratory and cardiovascular system.
The key to successful pre-hospital management of anaphylaxis/allergic reaction is prompt
recognition and treatment. Following critical interventions of airway, breathing and circulation
control, attention is focused on reversing the effects of histamine. Epinephrine helps reverse the
effects of histamine, supports the blood pressure, and reverses capillary leakage.
Diphenhydramine blocks the effects of histamine release by competing for histamine receptor sites.
Salbutamol is useful for reducing bronchoconstriction. And where certified, IV fluid therapy is
crucial in treating hypovolemia and hypotension.
Southwest Ontario Regional Base Hospital Program
London • Owen Sound • Windsor
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Anaphylaxis/Allergic Reaction Protocol
When the following conditions exist, a Paramedic may administer epinephrine (1:1000)
subcutaneously (SC) or intramuscularly (IM), and/or Diphenhydramine (Benadryl) intravenously (IV)
or intramuscularly (IM) according to the following protocol. A maximum of two (2) doses of
epinephrine and one (1) dose of Diphenhydramine may be administered regardless of any previous
self-administration.
Indications
Patient has a confirmed or suspected history of exposure to a probable allergen
AND
a. Demonstrates signs and symptoms of a severe anaphylactic reaction for administration
of epinephrine and Diphenhydramine
OR
b. Demonstrates signs and symptoms of a moderate allergic reaction for administration of
Diphenhydramine.
Procedure
1. Ensure a patent airway, administer 100% 02, and document vital signs.
2. Initiate cardiac monitoring and pulse oximetry (if available).
3. If evidence of a severe reaction, administer epinephrine (1:1000) SC/IM using a 1 ml syringe:
 0.01mg/ kg SC/IM (rounded to nearest 0.05 mg) to a maximum dose of 0.3 mg SC/IM.
OR
For services that only carry epinephrine auto injector(s):
 Patient < 10 kilograms: contact Base Hospital Physician (BHP). If not able to contact the
BHP and allergic signs and symptoms worsening consider pediatric epinephrine auto
injector (0.15mg) and continue attempting contact with BHP
 Patient ≥ 10 kilograms and < 30 kilograms: administer pediatric epinephrine auto injector
(0.15mg)
 Patient ≥ 30 kilograms: administer epinephrine auto injector (0.3mg)
4. Transport to hospital immediately after the administration of the first dose of SC/IM epinephrine.
If reassessment reveals that the patient’s clinical condition has not significantly improved 10
minutes after the initial dose, the Paramedic can repeat the dosage of epinephrine SC/IM once.
5. Caution - in patients <10kg, or in patients with ischemic heart disease. For these patients the
BHP should be contacted before a second dose is administered. If every attempt to contact the
BHP has failed and the patient is not improving a second dose may be given. The paramedic
should continue to attempt to contact the BHP.
Southwest Ontario Regional Base Hospital Program
London • Owen Sound • Windsor
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Anaphylaxis/Allergic Reaction Protocol (Continued)
6. Paramedics certified in IV initiation and fluid management should attempt IV access if not
already done. Consult the Intravenous Access & Fluid Administration Protocol.
7. Administer Diphenhydramine for a moderate reaction or for a severe reaction after epinephrine
has been administered:
 <25kg = Required Patch
 25kg to 49kg = 25mg or 0.5ml
 ≥50kg = 50mg or 1.0ml
Notes
1. If the patient has wheezing as a feature of the anaphylaxis, they should be additionally
considered for the SOB/Respiratory Distress Protocol after the paramedic has administered the
first dose of epinephrine.
2. Urticaria on its own does not constitute a severe life-threatening anaphylactic reaction. At least
one other sign must be present before giving epinephrine.
3. If at any time the symptoms become severe then the patient should be considered for
epinephrine.
4. Pediatric Epinephrine Dosing Chart:
The following chart describes the dosage for pediatric Epinephrine based on the formula: [(age
x 2) + 10 kg] x 0.01, rounded to closest 0.05 mg (ml).
Age
0-6 M
6-12 M
1
2
3
4
5
6
7
8
9
10
Weight kg
(2 x age) + 10
12
14
16
18
20
22
24
26
28
30
DOSE
mg or ml
0.05
0.10
0.10
0.15
0.15
0.20
0.20
0.20
0.25
0.25
0.30
0.30
100 Unit/1cc
Syringe
05 Units
10 Units
10 Units
15 Units
15 Units
20 Units
20 Units
20 Units
25 Units
25 Units
30 Units
30 Units
Southwest Ontario Regional Base Hospital Program
London • Owen Sound • Windsor
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Anaphylaxis/Allergic Reaction Protocol Diagram
Notes
1. If the patient has wheezing as a feature of the anaphylaxis, they should be additionally
considered for the SOB/Respiratory Distress Protocol after the paramedic has administered the
first dose of epinephrine.
2. Urticaria on its own does not constitute a severe life-threatening anaphylactic reaction. At least
one other sign must be present before giving epinephrine.
3. Caution in patients <10kg, or in patients with ischemic heart disease. For these patients the
BHP should be contacted before a second dose is administered. If every attempt to contact the
BHP has failed and the patient is not improving, a second dose may be given. The paramedic
should continue to attempt to contact the BHP.
Southwest Ontario Regional Base Hospital Program
London • Owen Sound • Windsor
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