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Ritu Sahni “WHAT’S THE CALL?” This question is on the minds of most EMS responders as they exit their quarters. Our introduction to the patient is typically the “chief complaint,” which is relayed to the responding crew by dispatch. This is universal in the EMS world, whether it is a 9-1-1 ambulance call, a critical care air ambulance response, or a search-and-rescue call. This information can bring two outcomes: The field provider can be well prepared for the upcoming call, or the field provider can be led astray. This section focuses on a systematic review of patient care based on a chief complaint. Each chapter highlights the evaluation, differentiation, and management of individual chief complaints. A key point, however, is also a discussion of the pitfalls accompanying each chief complaint. C SE C TION Individual Chief Complaint Protocols Pitfalls can occur when a particular sign or symptom that pointed to a more critical situation is missed or when the chief complaint is not easily related to the actual problem. In many cases, the authors outline these pitfalls so that errors of both commission and omission can be avoided. In addition, this section contains a special chapter authored by Andrew Travers and Ron Stewart that tackles the problem of the “undifferentiated patient.” Although the initial concept revolves around dispatch information that makes categorization difficult, it leads to a thoughtful discussion of prehospital decision making. Although most EMS agencies have protocols that may be based on presenting complaint (e.g., chest pain) or presenting condition (e.g., cardiac arrest), the topics reviewed in these chapters can be the basis for protocols based on either. 203 1_C_21_203-210.indd 203 12/3/08 5:57:18 PM 1_C_21_203-210.indd 204 12/3/08 5:57:19 PM CH APTER Allergies/Stings 21 Debra Perina Leslie F. Smith INTRODUCTION Patient concern for potential allergic reactions is a common complaint resulting in calls for EMS response. Allergic reactions can be triggered by a myriad of different agents, such as foods, medications, topical agents, and environmental exposures including arthropod stings. Severity can vary from discomfort to life threatening if left untreated. This chapter will focus on allergic reactions from bites or stings. EMS medical directors must be familiar with recognition of allergic reactions and anaphylaxis, prehospital response capabilities, and treatments in the prehospital environment. PHYSIOLOGY OF ALLERGIC REACTIONS Allergic reactions can vary from very mild, with only symptoms of pruritus or rash, to full-blown anaphylaxis along the continuum of disease. Anaphylaxis is a potentially life-threatening hypersensitivity reaction that carries a significant risk of vascular collapse and/or respiratory compromise. Allergic reactions are hypersensitivity reactions resulting from the exposure to an allergen.1 There are four types of hypersensitivity reactions (Table 21.1). Type I accounts for most cases of anaphylaxis. Type III is most commonly seen in reactions to blood transfusions and with immunoglobulin therapy. Reactions typically present with urticaria that can progress to angioedema (facial or tongue swelling) followed by respiratory distress, dizziness, syncope, and shock. Angioedema is very concerning because it can progress rapidly to life-threatening airway compromise. Angioedema can be medication induced or genetic. One of the more common causes is angiotensin-converting enzyme (ACE) inhibitors. Often the patient has been taking this medication for some time before such a reaction occurs, which can be confusing to some who assume that a reaction would have occurred sooner if the patient was going to exhibit one. Hereditary angioedema is an autosomal dominant genetic disorder caused by a defect in the complement pathway that results in either a low C1 esterase level or a high level of dysfunctional C1 esterase. Patient symptoms can include pruritus, urticaria, wheezing, facial and tongue swelling, dizziness, hypotension, syncope, and gastrointestinal distress.2 CAUSATIVE AGENTS Almost anything can be a potential allergen. Common agents include medications, foods and food additives, latex, arthropod bites and stings, mold, radiographic contrast media, and certain marine envenomations ¹(see Chapter 17, Animal Bites; Table 21.2). Some insect bites or stings, such as those of millipedes, caterpillars, and centipedes, most often cause only pain and local skin reactions such as blistering.3,4 Certain species of caterpillars have venom-filled hair and spines that can cause systemic reactions, including anaphylaxis, within 2 hours of the sting.3 Some offenders, such as the Gila monster, can remain attached to the patient. Bites from kissing bugs are painless and usually occur during sleep. Most often this results in localized swelling at the bite site but can progress 205 1_C_21_203-210.indd 205 12/3/08 5:57:19 PM TABLE 21.1 Types of Hypersensitivity Reactions Type I Type II Immediate Cytotoxic Type III Type IV Immune Complex Delayed Mediator Anaphylaxis Cause IgE or IgG4 Complement cascade IgG or IgM IgG or IgM T-cell Most common Yes Yes No IgE, immunoglobulin E; IgG, immunoglobulin G; IgM, immunoglobulin M. to systemic reactions.5 There are also occasional rare reports of anaphylaxis from the bites of horse flies, deer flies, rats, and mice. Hymenoptera account for the majority of severe allergic responses and anaphylaxis episodes related to insect bites. There are three families of Hymenoptera: bees (honeybees and bumblebees), vespids (yellow jackets, hornets, and wasps), and stinging ants (fire ants). Since fire ants are in the Hymenoptera family, the venom in fire ant bites is identical to that of bees and hornets so that patients allergic to beestings will also display an allergic reaction to a fire ant bite.6 Africanized honeybees (“killer bees”) are an aggressive hybrid of the honeybee and have the same venom, but they sting repeatedly, thus increasing the risk of a severe reaction.7 About 1% of children and 3% of adults have reportedly had severe systemic allergic reactions to Hymenoptera venom.8 Anaphylaxis can occur even with the first episode. Insect stings are the only allergen for which specific immunotherapy currently exists. This is most likely due to the prevalence and severity of such responses in humans.9 ASSESSMENT AND GENERAL APPROACH The first step in EMS response to calls regarding allergic reactions and/or bites and stings is ensuring that the scene is safe. Provider and patient safety should be paramount because no rescue or treatment can occur if providers fall victim to the same process that is affecting the patient. Next, EMS providers should determine how the patient was stung or what activity was occurring before the allergic reaction. This will help the 206 1_C_21_203-210.indd 206 SECTION C provider determine if there is any special treatment needed and if there is the potential for development of a severe reaction or anaphylaxis. EMS personnel should take all proper equipment, including life support, emergency drugs, and monitoring equipment with them when initially approaching the patient. Failure to do so may delay necessary treatment and result in further physiologic decompensation of the patient. Patient assessment should rapidly be done to ensure a patent airway. The patient should be queried for shortness of breath or dysphagia, and the provider should note if the patient’s voice is hoarse. The EMS provider should listen to breath sounds, assessing for stridor or wheezing. Facial, tongue, or orbital swelling should be noted. A full set of vital signs should be taken. The patient should be evacuated from the scene as soon as feasible to prevent further contact with the allergen. If the patient is in extremis and airway control is necessary, consideration should be given to requesting additional responders. Continued patient assessment should center on ensuring a patent airway and continuously monitoring vital signs. All patients with significant allergic reactions or potential for deterioration during transport should have at least one large-bore IV line started with normal saline. The patient should be transported expediently to the closest most appropriate facility depending on availability of local resources and other factors such as distance, weather, and terrain. Prehospital Treatment EMS medical directors should ensure that personnel provide appropriate prehospital care to patients suffering an allergic reaction or anaphylaxis. If the patient has been stung or bitten, providers should be wary to Individual Chief Complaint Protocols 12/3/08 5:57:20 PM TABLE 21.2 Common Causes of Allergic Reactions Medications Antibiotics Penicillin, vancomycin, trimethoprimsulfamethoxazole ACE inhibitors Aspirin Nonsteroidal anti-inflammatory drugs Radiographic iodine based dyes Human/Animal Proteins Vaccines Transfusions Foods Peanuts/nuts Eggs Wheat Shellfish, soybeans wheat Additives Red dye Sulfites Animals Stings/Insects Hornets/wasps Fire ants Scorpion Caterpillars Kissing bugs Centipedes Millipede Arachnids Ticks Vertebrates Lizards Gila monster Marine bites Sea nettle Man-of-war Jellyfish Mammals Rats/mice Gerbils Hamsters Other Mold Latex ensure they also are not affected. The patient should be removed from the area, and if necessary, decontaminated. BLS evaluation should be the first priority to ensure a patent airway, adequate oxygenation, and intact circulation. If the patient is in respiratory distress or wheezing, 100% oxygen should be given to the patient with a non-rebreather mask. A largebore IV with normal saline should be started and a fluid bolus of at least 500 ml given. If the patient was stung, any wounds should be inspected for retained stingers. If discovered, removal should be accomplished by scraping across the sting with a rigid thin object, such as an identification badge, to dislodge the stinger. Forceps or other squeezing devices should not be used because they may inadvertently disrupt the venom sac and release more venom into the patient. Local wound care with cool compresses and gauze covering should be applied. If there is the possibility of injected venom, the patient should be kept still and the affected extremity should be kept below the level of the heart to keep the venom from spreading.10,11 If there is only a local isolated reaction, patient comfort and pain relief is all that is necessary. However, if the patient has a systemic allergic response, there is need for additional medications. Several medications are useful in this setting, and their use will depend on the severity of the patient’s symptoms, vital signs, and past medical history. Before administering any medication, the provider should ensure that the patient has no medication allergies. The provider should also determine if the patient has taken any of his or her own medication (e.g., epinephrine autoinjector, oral diphenhydramine, or other oral antihistamine) before EMS arrival that may be masking the severity of the reaction or affect any of the medications EMS will administer. If the patient has his or her own autoinjector, EMS personnel of all training levels may assist with administration. Research has demonstrated that epinephrine autoinjectors can be used safely by EMTs in the treatment of anaphylaxis in the field.12 Antihistamines are by far the most commonly used class of medication. Antihistamines block the action of histamine at H1 receptors, but do not decrease histamine release. Diphenhydramine is the most common medication in this class and can be given orally, intravenously, intraosseously, or intramuscularly in a typical dose of 25 to 50 mg for adults. Research is suggestive that H2 blockers have a synergistic CHAPTER 21 1_C_21_203-210.indd 207 Allergies/Stings 207 12/3/08 5:57:20 PM action when used in conjunction with diphenhydramine, blocking both cellular histamine receptors.13 Both famotidine and ranitidine are useful H2 blockers, but cimetidine is not recommended due to its multiple drug interactions. Adult doses are IV famotidine 20 mg or IV ranitidine 50 mg. Corticosteroids, either orally or intravenously, may also be useful to prevent return of symptoms once other medications are metabolized. Peak onset of action of corticosteroids is 2 to 4 hours. Nebulized beta-agonists, such as albuterol, can be used for patients with persistent bronchospasm. Nebulized ipratropium bromide may also be used. Although both the multidose inhaler and the nasal spray formulations of ipratropium contain an ingredient (soy lecithin, used to keep the medication in suspension) that may cause an allergic reaction in patients with known peanut allergies, the nebulized formulation typically used by EMS and emergency departments lacks this ingredient.2 All of the aforementioned drugs may also be used in children, but as with any pediatric medication, dosages must be calculated based on the child’s weight (Table 21.3). Epinephrine is the first-line medication in a patient with anaphylaxis. However, it should be used with caution in patients over 50, those with known coronary artery disease, or in cases with lifethreatening tachydysrhythmias because cardiac ischemia and myocardial infarction may be precipitated and have been reported.14 Two different concentrations of TABLE 21.3 Pediatric Allergic Reaction Treatment Drug Dosages Drug Weight-Based Dose Epinephrine 0.01 mg/kg of 1:1000 IM 1 ml of 1:10,000 mixed with 10 ml NS Diphenhydramine Methylprednisolone Famotidine Ranitidine 0.5 ml of 1:1000 in 2.5 ml NS nebulized 1 mg/kg IM/IV/IO/PO to max of 50 mg 1–2 mg/kg 0.5 mg/kg to max of 20 mg IV/IO 2–4 mg/kg to max of 50 mg IV/IO IM, intramuscularly; IO, intraosseously; NS, normal saline; PO, by mouth. 208 1_C_21_203-210.indd 208 SECTION C epinephrine may be used, and the provider must exercise great caution to use the proper dosage and formulation when administering it. In adults, epinephrine 0.3 ml of 1:1000 solution can be given subcutaneously or intramuscularly if the patient is not on the verge of cardiovascular collapse. If the patient is hemodynamically unstable, epinephrine 1 ml of 1:10,000 mixed with 10 ml of normal saline can be given slowly by IV or intraosseous push over 5 to 10 minutes. Epinephrine may also be nebulized by placing 0.5 ml of 1:1000 solution in 2.5 ml of normal saline. Epinephrine should be given via the intramuscular route whenever feasible. It has been demonstrated that this route produces higher peak plasma concentrations in less time than injection subcutaneously in the deltoid.15 Intramuscular injection in the thigh results in particularly fast absorption and is thought to be due to the increased vascularity of the vastus lateralis muscle.5 If the patient is hypotensive, aggressive fluid resuscitation with 1 to 2 L of normal saline is indicated in addition to the aforementioned medications. Patients will become intermittently hypotensive and require multiple fluid boluses and additional medications en route, so frequent monitoring of vital signs is imperative. Localized angioedema is treated as an allergic reaction with antihistamines, steroids, and epinephrine in severe cases. However, little actual benefit or significant improvement has been shown with these medications. The mainstay of treatment is supportive, with early consideration for intubation. If the decision to intubate is made, great concern and preparation should be taken because the edema can extend to the glottic and subglottic regions. This may not be externally visible, and the only clue the provider may have is that the patient’s voice is hoarse or different than normal. If subglottic and/or glottic edema is present, intubation may be fraught with difficulty, and the provider should be prepared for a difficult airway including emergency rescue techniques, such as cricothyrotomy, especially if rapid-sequence intubation (RSI) is also being employed.16 As with medication-induced angioedema, hereditary angioedema is generally not responsive to antihistamines, steroids, and epinephrine.5 SPECIAL CONSIDERATIONS Several points may be helpful to remember when responding to allergic reaction calls in the prehospital environment. In general, stinging insects, especially Hymenoptera, can cause systemic allergic reactions Individual Chief Complaint Protocols 12/3/08 5:57:21 PM and anaphylaxis, but these reactions are rare with biting insects.17 There is a greater chance of a systemic reaction with multiple stings. One should remember that the clinical presentation may be quite varied and the history vague. Care should be taken to frequently reassess the patient and document pertinent findings, which may be the first clue that an allergic reaction is present if the patient does not relate an exposure or inciting event. Symptoms can be exacerbated by fear, exercise, alcohol intake, heat exposure, or underlying cardiovascular disease. The provider should be careful not to become complacent or attribute clinical signs and symptoms solely to these conditions because allergic reactions can progress insidiously. Anaphylaxis to stings can occur years after the first exposure, even without intervening stings. If the patient experiencing a severe allergic reaction or anaphylaxis routinely takes beta-blocker medications, the action of epinephrine may be blunted. Glucagon may be given in 1-mg increments by any parenteral route to overcome the effects of beta blockade. Cutaneous symptoms are the most common clinical response in both adults and children. Hypotension is uncommon in children, but it has been reported in up to 60% of adults.18 Patients will sometimes complain of chest pain or shortness of breath before development of a more generalized severe allergic reaction. EMS providers should have a high index of suspicion on calls with these complaints to ensure that there was no contact with an allergen that may have caused these symptoms. For instance, radiocontrast media are frequently given in free-standing imaging centers. Consider the possibility of allergic reactions and anaphylaxis when responding to calls of shortness of breath or chest pain in these facilities.19 Anaphylaxis should be one of the etiologies considered when responding to cardiac arrests in outside areas, such as golf courses, because the patient may have been stung before the cardiac arrest. Although bites from a Gila monster are infrequent, if it is still attached to the patient, the provider should remove it by either prying its jaws apart with a stick or metal object, holding a flame under the lizard’s chin, or submerging it in cold water.20 Care should be taken to avoid additional bites to the patient or the providers. To determine the most appropriate destination facility for allergic reaction patients, it helps to consider the etiology of the reaction and the availability of certain subspecialties, such as otolaryngology, anesthesia, critical care, toxicology, and so on, which may be necessary to definitively treat the reaction. Transportation time should also be considered. If the patient is unstable or is likely to become unstable during an extended transport time to an appropriate facility, aeromedical evacuation should be strongly considered. Direct medical oversight can assist with these decisions. SUMMARY Allergic reactions and anaphylaxis are frequently seen in the prehospital environment. EMS providers should be alert to the potential for rapid progression of allergic reactions and be prepared to support the patient hemodynamically and provide appropriate airway management. All patients should be provided with oxygen, IV fluid administration, and continuous monitoring during transport. Providers should be familiar with the common medications and the dosages used to treat allergic reactions. Rapid transport to an appropriate hospital should occur as soon as feasible. C L I NI C A L VI G N E T T E S Case 1 An 88-year-old female calls 9-1-1 after accidentally taking her husband’s penicillin. She has a history of coronary artery disease and a severe penicillin allergy. When EMS personnel arrive, they find an anxious elderly female. The patient is assessed and an IV line obtained. En route to the hospital she complains of itching, and hives are noted. She does not have any respiratory complaints and lungs are clear to auscultation. Epinephrine and diphenhydramine injections are prepared. Diphenhydramine is administered intravenously, and epinephrine is held ready as a precaution. After getting the IV injection, she complains of severe chest pain and palpitations. CHAPTER 21 1_C_21_203-210.indd 209 Allergies/Stings 209 12/3/08 5:57:21 PM What is the most likely cause of the patient’s symptoms? a. anxiety b. inadvertent epinephrine administration c. progression of the anaphylaxis reaction d. reaction to diphenhydramine The answer is b. As stated in the chapter, epinephrine must be used with care in the population at risk for coronary artery disease because it can, theoretically, produce ischemia. Case 2 A previously healthy 30-year-old male is working in the yard when he feels a sharp sting. A few minutes later, he has intense itching and notices red wheals spreading across his arm. He has a history of allergies to bees and calls 9-1-1. EMS personnel arrive to find him complaining of difficulty catching his breath. After making sure that the scene is safe and applying oxygen, what should rescuers consider next? a. albuterol aerosol b. diphenhydramine intramuscularly c. epinephrine intramuscularly d. epinephrine subcutaneously e. prednisone by mouth The answer is c. In a patient who is obviously anaphylactic, epinephrine should be the frontline treatment. In addition, it is best given to the “borderline” patient early before he or she becomes floridly anaphylactic. REFERENCES 1. Ewan PW. Anaphylaxis. BMJ 1998; 316: 1442. 2. Kemp SF. Current concepts in pathophysiology, diagnosis, and management of anaphylaxis. Immunol Allergy Clin North Am 2001; 21: 611–634. 3. Norris R. Caterpillar envenomations, www.EMedicine.com, 2007. 4. Norris R. Millipede envenomations, www.EMedicine.com, 2007. 5. Clark RF. Arthropod bites and stings. In Emergency Medicine: A Comprehensive Study Guide, 5th ed. New York: McGraw-Hill, 2000, pp1242-1251. 6. deSchazo RD, Butcher BT, Banks WA. Reactions to the stings of the imported fire ant. N Engl J Med 1990; 323: 462. 7. Klotz JH, Klotz SA, Pinnas JL. Animal bites and stings with anaphylactic potential. J Emerg Med; Nov 8, 2007 [Epub ahead of print]. 8. Yates AB, Moffitt JE, deShazo RD. Anaphylaxis to arthropod bites and stings. Immunol Allergy Clin North Am 2001: 21: 635–651. 9. Graft DF. Insect sting allergy. Med Clin N Am 2006; 90: 211–232. 10. Pinnas JL. Allergic reactions to insect stings. In Conn’s Current Therapy. Philadelphia: WB Saunders, 2001, pp. 797–799 11. Rowe BH, Carr S. Anaphylaxis and acute allergic reactions. In Emergency Medicine: A Comprehensive Study Guide, 6th ed. New York: McGraw-Hill, 2004, pp. 247–251. 210 1_C_21_203-210.indd 210 SECTION C 12. Gold MS, Sainsbury R. First aid anaphylaxis management in children who were prescribed an epinephrine autoinjector device (EpiPen). J Allergy Clin Immunol 2000; 106: 171. 13. Lin RY, Curry A, Pesola GR, et al. Improved outcomes in patients with acute allergic syndromes who are treated with combined H1 and H2 antagonists. Ann Emerg Med 2000; 36: 462–468. 14. Anchor J, Settipane R. Appropriate use of epinephrine in anaphylaxis, Am J Emerg Med 2004; 22(6): 488–490 15. Estelle F, Simons R, Gu X, et al. Epinephrine absorption in adults: Intramuscular versus subcutaneous injection. J Allergy Clin Immunol 2001; 108: 871–873. 16. Muelleman RL, Tran TP. Allergy, hypersensitivity, and anaphylaxis. In Rosen’s Emergency Medicine Concepts and Clinical Practice, 5th ed., vol 2. New York: Mosby, 2002, pp.1619–1633. 17. Golden DB. Insect sting anaphylaxis. Immunol Allergy Clin N Am 2007; 27(2): 261–266. 18. Moffitt JE, Golden DB, Reisman RE, et al. Stinging insect hypersensitivity: A practice parameter update. J Allergy Clin Immunol 2004; 114: 869. 19. Pumphrey RS. Lessons for management of anaphylaxis from a study of fatal reactions. Clin Exp Allergy 2000; 30: 1144. 20. Piacentine J, Curry SC, Ryan PJ. Life-threatening anaphylaxis following gila monster bite, Ann Emerg Med 1986; 15(8): 959–961. Individual Chief Complaint Protocols 12/3/08 5:57:22 PM