Primary Care Paramedic Diphenhydramine (Benadryl) Certification Package 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. Page 2 of 9 2
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 Page 3 of 9 3
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. Page 4 of 9 4
Mild Allergic Severe Allergic Reaction or Reaction Anaphylaxis Onset Gradual 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 bronchoconstriction Severe bronchoconstriction (wheezing), laryngospasm (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 Mental Status Normal Management of Allergic Reactions/Anaphylaxis blood pressure Anxiety, sense of impending doom, progressing to 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 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 Page 5 of 9 5
(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. Page 6 of 9 6
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. Page 7 of 9 7
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 Weight kg (2 x age) + 10 DOSE mg or ml 100 Unit/1cc Syringe 0-6 M 0.05 05 Units 6-12 M 0.10 10 Units 1 12 0.10 10 Units 2 14 0.15 15 Units 3 16 0.15 15 Units 4 18 0.20 20 Units 5 20 0.20 20 Units 6 22 0.20 20 Units 7 24 0.25 25 Units 8 26 0.25 25 Units 9 28 0.30 30 Units 10 30 0.30 30 Units Page 8 of 9 8
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. Page 9 of 9 9