Culicosis bullosa =داء لدغ البعوض الفقاعي |
Insect Bites
Insects are arthropods of the class Insecta. Insects have an adult stage characterized by a hard exoskeleton, 3 pairs of jointed legs, and a body segmented into head, thorax, and abdomen. Insects comprise the most diverse and numerous class of the animal kingdom and include numerous species of praying mantis, dragonflies, grasshoppers, true bugs, flies, fleas, bees, wasps, ants, lice, butterflies, moths, and beetles. The number of species is estimated at between 6 and 10 million, with more than a million species already described. Insects represent more than half of all known living organisms and potentially represent more than 90% of the differing life forms on Earth. Hence, human contact with insects is unavoidable. Exposure to biting or stinging insects or to their remains can range in severity from benign or barely noticeable to life threatening. A stinging apparatus is usually a sharp organ of offense or defense, especially when connected with a venom gland, and adapted to inflict a wound by piercing, as the caudal sting of a scorpion. The stinger is typically located at the rear of the animal. Animals with a stinger include bees, wasps, hornets, and scorpions. Most stinging insects are of the order Hymenoptera, which includes ants, bees, and wasps. Hymenoptera stings result in more fatalities than stings or bites from any other arthropod. Wasps can bite and sting at the same time (See Wasp Stings). While illness related to insect exposure in a particular locale may be easily recognizable, the emergency physician must also be aware of more exotic insect-related diseases as humans travel to more remote areas of the country and the world. Additionally, exotic insects are often kept as pets (sometimes illegally) or can be encountered in shipments of foreign origin. Anaphylactic shock Anaphylactic shock is the most notable immediate risk associated with insect exposures. Hypersensitivity to otherwise harmless insect saliva, venom, body parts, excretions, or secretions can cause systemic responses in some individuals. Diagnosing the early phases of a systemic allergic reaction preceding anaphylactic shock is of paramount importance in treating any patient in whom insect exposure is suspected. Severe anaphylaxis can be fatal in as little as 10 minutes. The need to be aware of diseases transmitted by insect bites is crucial; Lyme disease, transmitted by ticks, and malaria, transmitted by mosquitoes, are discussed in other articles (see Tick-borne Diseases, Lyme; Malaria). Chagas disease, increasingly found in the desert southwest and in persons residing in or traveling to Central America or South America, should be considered, particularly when the bite site is on the soft skin of the periorbita or lips.2 Because this infection may produce an acute and chronic illness with notable morbidity and mortality, especially in pediatric patients, clinicians should maintain a high index of suspicion (see Trypanosomiasis). Mosquito and tick-borne encephalitides such as those produced by the eastern equine virus or the West Nile virus also should be considered in patients presenting with meningismus (see Encephalitis). Of note, some illnesses transmitted by insects do not produce symptoms until long after the infecting bite. In South America and parts of Africa, blackflies (Simuliidae) are responsible for transmission of onchocerciasis. This illness is also known as river blindness and eventually can produce blindness years after the initial infection. This disease is extremely rare in the United States. Chagas disease, a leading cause of cardiomyopathy in the world, may present latently as well. Obtaining a history of international travel is important because this information can lead to a diagnosis that would otherwise be overlooked. Determining the destination, time of year, length of stay, and time since travel are all important pieces of history to obtain. Exposure to arthropods may produce dermatitis, cellulitis, urticaria, or blistering unrelated to biting or stinging. Some species of moths, caterpillars, centipedes, beetles, and spiders have urticating hairs or secretions that can cause cutaneous irritation. For further information, please refer to the respective articles on these exposures (see Differentials). An uncommon occurrence in North America is myiasis by fly larvae. Fly larvae enter the host through varying mechanisms ranging from oviposition of live, burrowing larvae on the host, on or near open wounds, to attachment to other bloodsucking insects. While not generally the result of an insect bite, myiasis can produce pustules and lesions similar to insect bites. These lesions generally contain one or more developing fly larvae. Severe cases of myiasis can cause seizures. While plant-eating phytophagous insects can bite in self-defense, their bites generally are not purposeful. This article is limited to discussion of organisms that bite to feed on blood or to catch prey. Relatively harmless insects Cockroaches have been reported to bite humans, but their bite generally is harmless. Continued repeated exposure to their remains and feces poses a greater health threat, such as increased incidence of asthma, especially in inner cities, and their remains and feces are possible vectors for transmission of viral and bacterial diseases. Earwigs generally are harmless insects that have earned an unpleasant reputation. This may be because of their depiction in popular culture, such as in the television series, "The Night Gallery." Although they appear to have a large pincer on the posterior abdomen, it is not capable of rendering anything more serious than a mild pinch. Additionally, and contrary to popular belief, they do not routinely enter the human ear canal and parasitize humans. Cockroaches are much more likely to be found lodged in a patient's auditory passage. PathophysiologyMouthparts of biting insects can be classified into 3 broad groups: piercing, sponging, and biting. Tremendous diversity exists in the morphology of these groups. Insects discussed in this article generally are nonvenomous, yet many species inject saliva while biting. Their saliva may aid in digestion, inhibit coagulation, increase blood flow to the bite, or anesthetize the bite locus. Most lesions are the result of the victim's immune response to these insect secretions. In the case of Chagas disease, the infective organism is transmitted via the feces of a reduviid bug, which enters through the bite site when the wound becomes pruritic and is scratched. Most insect bites are minor and can result in superficial puncture wounds to the skin. Horseflies feed with a large scissorlike proboscis that can cause a relatively deep and painful wound. Differentiating between insect bites and stings Many patients confuse an insect bite with a sting and may use the terms interchangeably. A bite is usually from mouth parts and occurs when an insect is agitated to defend itself or when an insect seeks to feed. Bites from mosquitoes, fleas, bed bugs, and mites are more likely to cause itching than pain.
Most patients are aware of insect bites when they occur or shortly thereafter, but because it is such a common occurrence, the exposure is typically dismissed unless a severe or systemic reaction occurs.
Physical
Physical examination elements indicating a systemic reaction include the following:
Prehospital Care
Emergency Department Care
Consultations
MedicationGoals of therapy are to treat anaphylaxis and prevent complications. Cardiovascular agentsAct to decrease the muscle tone in the small and large pulmonary airways and increase vascular tone. Epinephrine (Adrenalin, Bronitin, EpiPen)Drug of choice for shock, angioedema, airway obstruction, bronchospasm, and urticaria in severe anaphylactic reactions. Administer IM; administer IV to patients in extremis; may be administered SL or ET when no IV access available. Continuous infusion may be given in cases of refractory shock.
Adult1 mL 1:10,000 solution slow IV; repeat prn Pediatric0.01 mL/kg (min 0.1 mL) 1:10,000 solution IV prn
Epinephrine coadministered with other sympathomimetics may have additive effects; beta-blockers antagonize therapeutic effects of epinephrine; digitalis may potentiate proarrhythmic effects of epinephrine; TCAs and MAOIs potentiate cardiovascular effects of epinephrine; phenothiazines may decrease BP when coadministered with epinephrine
In a life-threatening anaphylactic reaction, epinephrine may be given with appropriate caution when any of the following relative contraindications are present: coronary artery disease; uncontrolled hypertension; serious ventricular dysrhythmias; second stage of labor
PregnancyB - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals PrecautionsCaution in elderly patients and those with prostatic hypertrophy, hypertension, cardiovascular disease, diabetes mellitus, hyperthyroidism, and cerebrovascular insufficiency; rapid IV infusions may cause death from cerebrovascular hemorrhage or cardiac dysrhythmias BronchodilatorsThrough activation of cyclic AMP, beta agonists stimulate the ATPase pump, thereby shifting potassium into the intracellular compartment and stimulating an adrenergic response. Albuterol (Ventolin)Beta agonist useful in treating bronchospasms refractory to epinephrine. Relaxes bronchial smooth muscle by action on beta2 receptors and has little effect on cardiac muscle contractility. Numerous inhaled beta agonists are used for treatment of bronchospasm; albuterol is used most commonly.
Adult0.5 mL 0.5% solution in 2.5 mL NS nebulized q15min Pediatric0.03-0.05 mL/kg 0.5% solution in 2.5 mL NS via nebulizer q15min
Increases toxicity of beta-blocking and alpha-blocking agents and halogenated inhalational anesthetics
May be given in a life-threatening anaphylactic reaction, even when the following relative contraindications are present: severe coronary insufficiency; uncontrolled severe hypertension
PregnancyB - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals PrecautionsCaution in elderly patients and those with prostatic hypertrophy, hypertension, cardiovascular disease, diabetes mellitus, hyperthyroidism, and cerebrovascular insufficiency; rapid IV infusions may cause death from cerebrovascular hemorrhage or cardiac dysrhythmias AntihistaminesPrevent histamine response in sensory nerve endings and blood vessels; more effective in preventing histamine response than in reversing it. H2 antihistamines are useful in treatment of anaphylactic reactions when used concomitantly with H1 antagonists. Many H2 blockers are available. Cimetidine is the prototype drug. Diphenhydramine (Benadryl)Used for symptomatic relief of allergic symptoms caused by histamines released in response to allergens; many effective H1 blockers; diphenhydramine is effective and widely available.
Adult50 mg PO q4-6h Pediatric5 mg/kg/d PO divided q6h-8h
Potentiates effect of CNS depressants; due to alcohol content, do not give syr dosage form to patient taking medications that can cause disulfiramlike reactions
Documented hypersensitivity; MAOIs
PregnancyC - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus PrecautionsMay exacerbate angle-closure glaucoma, hyperthyroidism, peptic ulcer, and urinary tract obstruction Cimetidine (Tagamet)An H2 antagonist that, when combined with H1 type, may be useful to treat itching and flushing in anaphylaxis, pruritus, urticaria, and contact dermatitis that do not respond to H1 antagonists alone. Use in addition to H1 antihistamines.
Adult300 mg PO/IV/IM q6h Pediatric5-10 mg/kg PO/IV/IM q6h
Can increase blood levels of theophylline, warfarin, TCAs, triamterene, phenytoin, quinidine, propranolol, metronidazole, procainamide, and lidocaine
Documented hypersensitivity
PregnancyC - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus PrecautionsElderly patients may experience confusional states; may cause impotence and gynecomastia in young males; may increase levels of many drugs; adjust dose or discontinue treatment if changes in renal function occur Corticosteroid, SystemicHave anti-inflammatory properties and cause profound and varied metabolic effects. In addition, these agents modify the body's immune response to diverse stimuli. Prednisone and methylprednisolone are typical drugs of this class. Oral bioavailability is generally similar to parenteral; administer oral prednisone when indicated if a patient is not in extremis and can comfortably take PO; administer parenteral steroid when indicated for a patient in more severe circumstances. PrednisoneBelieved to ameliorate delayed effects of anaphylactic reactions and may limit biphasic anaphylaxis. Doses below are general guidelines for usage; dosing is highly individualized.
Adult40-60 mg/d PO qd or divided bid/qid; no taper required if used for 5-7 d. Pediatric1-2 mg/kg PO qd or divided bid/qid; no taper required if used for 5-7 d.
Coadministration with estrogens may decrease clearance; concurrent use with digoxin may cause digitalis toxicity secondary to hypokalemia; phenobarbital, phenytoin, and rifampin may increase metabolism of glucocorticoids (consider increasing maintenance dose); monitor for hypokalemia with coadministration of diuretics
Documented hypersensitivity; viral infection, peptic ulcer disease, hepatic dysfunction, connective tissue infections, and fungal or tubercular skin infections; GI bleeding or ulceration
PregnancyB - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals PrecautionsAbrupt discontinuation of glucocorticoids may cause adrenal crisis; hyperglycemia, edema, osteonecrosis, myopathy, peptic ulcer disease, hypokalemia, osteoporosis, euphoria, psychosis, myasthenia gravis, growth suppression, and infections may occur with glucocorticoid use Methylprednisolone (Solu-Medrol, Depo-Medrol)Useful to treat inflammatory and allergic reactions. By reversing increased capillary permeability and suppressing PMN activity, may decrease inflammation.
Adult2-60 mg PO qd Pediatric1-2 mg/kg PO/IV/IM qd
NSAIDs may cause ulcers when taken concurrently; anticholinesterases may increase weakness in patients with myasthenia gravis when taken concurrently with steroids; risk exists of possible viral dissemination with live virus vaccines
Documented hypersensitivity; some evidence exists for fetal harm from corticosteroids (consider both benefits and risks of use during pregnancy); consider risks (eg, dissemination, activation, certain infections) when prescribing for immunosuppressed patients
PregnancyC - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus PrecautionsShort-term use of corticosteroids, even in large doses, has minimal harmful effects; long-term usage has multiple adverse effects; possible complications include hyperglycemia, edema, osteonecrosis, peptic ulcer disease, hypokalemia, osteoporosis, euphoria, psychosis, growth suppression, myopathy, or infections ToxoidsFor active immunity against tetanus. Tetanus toxoid adsorbed or fluidUsed to induce active immunity against tetanus in selected patients. The immunizing agents of choice for most adults and children > 7 y are tetanus and diphtheria toxoids. Necessary to administer booster doses to maintain tetanus immunity throughout life.
AdultPrimary immunization: 0.5 mL IM; give 2 injections 4-8 wk apart and a third dose 6-12 mo after second injection PediatricAdminister as in adults
Patients receiving immunosuppressants, including corticosteroids or radiation therapy, may remain susceptible despite immunization due to poor immune response; cimetidine may enhance or augment delayed-hypersensitivity responses to skin-test antigens; avoid concurrent use of medication with systemic chloramphenicol since it may impair amnestic response to tetanus toxoid; concurrent use of tetanus immune globulin may delay development of active immunity by several days (interaction is nevertheless clinically insignificant and does not preclude concurrent use)
Documented hypersensitivity; history of any type of neurologic symptoms or signs following administration of this product; FDA recommends that elective tetanus immunization be deferred during any outbreak of poliomyelitis because tetanus toxoid injections are an important cause of provocative poliomyelitis
PregnancyC - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus PrecautionsDo not use to treat actual tetanus infections or for immediate prophylaxis of unimmunized individuals (use instead tetanus antitoxin, preferably human tetanus immune globulin); diminished antibody response to active immunization may be seen in patients receiving immunosuppressive therapy; better to defer primary diphtheria immunization until immunosuppressive therapy discontinued; routine immunization of symptomatic and asymptomatic HIV-infected persons is recommended ImmunoglobulinsConsists of administration of immunoglobulins pooled from serum of immunized patients. Tetanus immune globulin (TIG)Used for passive immunization of any person with a wound that may be contaminated with tetanus spores.
AdultProphylaxis: 250-500 U IM in opposite extremity to tetanus toxoid lesion PediatricFor prophylaxis: 250 U IM in opposite extremity to tetanus toxoid
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