Bites and Stings
HYMENOPTERA STINGS
Hymenoptera (honeybees, bumblebees, wasps, hornets, fire ants, harvester ants, and yellow jackets) stings may produce local toxic reactions, local allergic reactions, local cellulitis, abscess formation, generalized urticaria, angioedema, serum sickness, and anaphylaxis, the last causing approximately 40 deaths each year in the United States. The order Hymenoptera is distinguished by the successful adaptation of the ovipositor (a tubular structure protruding from the abdomen, used for depositing eggs) such that the organ is additionally used to inject the insect’s venom.
Most Hymenoptera stings produce immediate pain followed by local itching, erythema, and edema, all of which generally resolve over 2 to 3 hours. Stings that occur directly into peripheral nerves may be associated with a local temporary paralysis.
Discussion of treatment is divided into that for acute (first 2 hours) and delayed presentations.
Acute Presentations
Local Reactions
Patients presenting acutely after a presumed Hymenoptera sting with only localized symptoms and signs should be questioned as to whether reactions have occurred in the past. Patients with no history of angioedema, bronchospasm, urticaria, or anaphylaxis should be observed for 1 to 2 hours and carefully monitored for evidence of evolving anaphylaxis; importantly, most patients with anaphylaxis have no history of significant reactions, and many deny any previous exposure. Patients with documented anaphylaxis caused by Hymenoptera envenomations in the past should receive prophylactic treatment as discussed in “Systemic Reactions.” The wound should be carefully examined for a stinger, which should be removed by gentle scraping to prevent further envenomation. Mouth parts or other foreign material should similarly be removed. The wound should be thoroughly cleansed, tetanus prophylaxis administered if appropriate, and ice applied. Patients who remain asymptomatic 2 hours after the injury may be discharged with instructions to return immediately if shortness of breath, wheezing, generalized pruritus, oropharyngeal swelling, or rash occurs. Instructions regarding local wound care and the possibility of local reactions should be provided as well.
Systemic Reactions
Adult patients who present with or develop generalized pruritus, urticaria, bronchospasm, or angioedema should immediately be treated with aqueous 1:1,000 epinephrine in a dose equal to 0.3 to 0.5 mg (0.3-0.5 mL); the pediatric dose is 0.01 mg/kg up to a maximum of 0.3 mg (0.3 mL); epinephrine in this setting should be administered subcutaneously. Caution should be used when weighing the risks and benefits of epinephrine administration in patients with preexisting
cardiovascular disease. Intravenous access should then be established and plans made for at least 2 to 4 hours, and up to 8 to 12 hours, of observation. Patients will also benefit from intravenous or intramuscular diphenhydramine, 50 mg in adults and 0.5 to 1.0 mg/kg in children. Ranitidine, 50 mg intravenous, or an analogous H2-blocker can also be administered, though the benefit is controversial. Steroids, although having little effect on the immediate reaction, should generally be given and may limit the course of urticaria and/or edema. Local wound care should be undertaken as in “Local Reactions” and a cool compress applied to the sting site to induce local vasoconstriction. Patients requiring treatment with epinephrine should be closely observed for evidence of recurring reactions.
Adults with significant bronchospasm should receive standard bronchodilatory therapy by nebulization. An early intravenous dose of methylprednisolone, 100 to 125 mg, or hydrocortisone, 500 mg, may be indicated and may prevent or lessen recurrences over the next 24 hours.
Patients who have minimal symptoms, who rapidly respond to therapy, and who remain asymptomatic after several hours of observation may be discharged; oral antihistamines may be helpful in reducing symptoms after discharge. Patients must be instructed to return immediately if symptoms recur.
Adult patients who present with anaphylaxis manifest as hypotension, shock, life-threatening or irreversible bronchospasm, or impending airway obstruction caused by laryngeal edema should immediately receive subcutaneous aqueous 1:1,000 epinephrine in a dose equal to 0.5 mg (0.5 mL); the pediatric dose is 0.01 mg/kg up to a maximum of 0.3 mg (0.3 mL), followed by intravenous diphenhydramine, 50 mg in adults and 0.5 to 1.0 mg/kg in children (up to 50 mg); intravenous ranitidine, 50 mg, can also be administered. In severe reactions, subcutaneous epinephrine may need to be readministered in 5-minute intervals for several doses. Importantly, adults presenting with anaphylaxis who are taking β-blockers should receive glucagon, 1 mg intravenous, which may need to be repeated at 5-minute intervals. In all patients, intravenous access should be established immediately, concurrent with the administration of subcutaneous epinephrine, and preparations for possible intubation, cricothyrotomy, or tracheostomy made. Normal saline should be rapidly infused to assist with blood pressure support. In patients not responding to the initial dose of epinephrine or with persisting and severe symptoms, aqueous 1:10,000 epinephrine, 1 to 2 mL, should be administered intravenously. This dose is equivalent to 0.1 to 0.2 mL of a 1:1,000 dilution and may be repeated if no response is observed or if significant symptoms persist. Cardiac monitoring should be initiated and maintained. The dose of intravenously administered epinephrine must be determined by the patient’s clinical condition, whether any response has occurred to the subcutaneous injection, and the possibility of precipitating cardiovascular complications. In addition, oxygen should be administered, and ice should be applied to the site.
Patients with inadequate ventilation or persistent cyanosis despite therapy require emergent intubation; patients with progressive respiratory obstruction or patients who are unable to be intubated because of local swelling require needle or surgical cricothyrotomy or tracheostomy. In the child younger than 12 years old, needle cricothyrotomy with a 14- or 16-gauge needle followed by pressure insufflation with 100% oxygen is indicated; adequate oxygenation may also be maintained in adults in this manner.
Prevention
Patients with reactions to Hymenoptera stings should be provided with and instructed in the use of any of the commercially available “bee sting” kits; kits contain
a tourniquet and injectable epinephrine. An EpiPen (epinephrine autoinjector) is commonly prescribed and will deliver 0.3 mg of epinephrine automatically; EpiPen Jr. is also available and delivers 0.15 mg of epinephrine. The Ana-Kit contains a syringe with two individually injectable 0.5 mL (0.5 mg) doses of epinephrine. Patients should also be advised to obtain an appropriate identification bracelet indicating their Hymenoptera allergy. Further measures to prevent subsequent envenomations involve avoiding scented toiletries and brightly colored clothing while outdoors and using an insect repellent containing diethyltoluamide when possible. Patients with systemic reactions should strongly consider Hymenoptera hyposensitization after discharge; therefore, referral to an allergist may be appropriate.
a tourniquet and injectable epinephrine. An EpiPen (epinephrine autoinjector) is commonly prescribed and will deliver 0.3 mg of epinephrine automatically; EpiPen Jr. is also available and delivers 0.15 mg of epinephrine. The Ana-Kit contains a syringe with two individually injectable 0.5 mL (0.5 mg) doses of epinephrine. Patients should also be advised to obtain an appropriate identification bracelet indicating their Hymenoptera allergy. Further measures to prevent subsequent envenomations involve avoiding scented toiletries and brightly colored clothing while outdoors and using an insect repellent containing diethyltoluamide when possible. Patients with systemic reactions should strongly consider Hymenoptera hyposensitization after discharge; therefore, referral to an allergist may be appropriate.
Delayed Presentations
Delayed reactions to stings are relatively common and result from four different mechanisms:
Local toxic reactions to venom
Local allergic reactions
Local infection
Systemic allergic reactions
Clear differentiation of the first three of these entities is extremely difficult clinically because all patients present with the signs and symptoms of local inflammation (redness, heat, swelling, and pain), and many patients with toxic and allergic reactions will have low-grade fevers. Infection is said to be somewhat more common after wasp, hornet, or yellow jacket stings than after bee stings; however, this is often not helpful in the individual patient. Infection is, however, unusual in the first 12 to 24 hours after injury. A practical approach to the treatment of patients with delayed presentations involves the use of both an antihistamine and an oral antibiotic. Diphenhydramine, 25 to 50 mg four times daily for 3 to 5 days, and a first-generation cephalosporin, for 5 to 7 days, are a reasonable treatment regimen. The wound should be thoroughly cleansed, examined for foreign material, and tetanus prophylaxis administered if needed. Elevation is advised if swelling is present; wounds that are fluctuant may require incision and drainage (see Chapter 44).
One should note the specific delayed or “toxic” reaction produced by the “killer bee.” These bees were imported into Brazil from Africa in 1956 and have now migrated into the southern United States via northern Mexico. Although the venom of the killer bee is similar to that of other bees, fatal and severe toxic reactions have been seen, primarily because of the bee’s aggressiveness and the large number of stings. As a result of the large amount of venom injected, direct toxic effects of the venom are produced; these typically evolve over 2 to 3 hours, as distinguished from anaphylactic reactions, and include fever, drowsiness, light-headedness, abdominal cramping, vomiting, diarrhea, and, in severe cases, seizures, coagulopathy, cardiovascular collapse, and death. Although less common, other delayed presentations include serum sickness, vasculitis, hemolysis, renal failure, and Henoch-Schönlein and thrombotic thrombocytopenic purpura.
HUMAN BITES
Human bites may occur intentionally or may be inadvertent; these inadvertent bites are often unrecognized, and therefore, therapy is inadequate or inappropriate. Inadvertent or accidental bites most frequently involve the hand when the face and mouth
are struck during an altercation (closed fist injury or CFI) or as a result of a “head-on” collision in sports. The human mouth contains a number of both aerobic and anaerobic organisms that may produce an extremely aggressive, necrotizing infection, particularly when the so-called closed spaces of the distal extremities are involved. Patients with CFIs require a careful evaluation of the wound along with plain films; integrity of tendons must be determined and foreign material (teeth) and/or fractures identified. One must remember that when striking an object, making a fist requires that the fingers are flexed; injuries will occur in this position. When evaluating such a wound, typically with the fingers extended, tendon injuries will therefore be missed, because they will now be proximal to the site of skin injury.
are struck during an altercation (closed fist injury or CFI) or as a result of a “head-on” collision in sports. The human mouth contains a number of both aerobic and anaerobic organisms that may produce an extremely aggressive, necrotizing infection, particularly when the so-called closed spaces of the distal extremities are involved. Patients with CFIs require a careful evaluation of the wound along with plain films; integrity of tendons must be determined and foreign material (teeth) and/or fractures identified. One must remember that when striking an object, making a fist requires that the fingers are flexed; injuries will occur in this position. When evaluating such a wound, typically with the fingers extended, tendon injuries will therefore be missed, because they will now be proximal to the site of skin injury.
Antibiotic Therapy
Preferred oral antibiotic therapy is recommended for 5 days and includes amoxicillin-clavulanate (Augmentin), 875 mg twice daily, dicloxacillin plus penicillin, a first-generation cephalosporin plus penicillin, or a fluoroquinolone (Ciprofloxacin, 500-750 mg every 12 hours). Children may be treated with Augmentin, 40 mg/kg/day in three equally divided doses. When parenteral treatment is required, ampicillinsulbactam (Unasyn), 1.5 to 3.0 g every 6 hours; cefoxitin, 1 to 2 g intravenous every 6 hours (pediatric dose is 80-160 mg/kg/day intravenous divided every 6 hours); or ticarcillin/clavulanate (Timentin), 3.1 g intravenous every 6 hours, is recommended. Penicillin-allergic patients can be given clindamycin plus ciprofloxacin.
Hospitalization
Given the difficulty in treating infection associated with human bites, a markedly reduced threshold for recommending hospital admission for parenteral antibiotic therapy is appropriate.
Superficial Abrasions or Minor Scrapes
Superficial abrasions or minor scrapes are occasionally produced, and these may be treated with thorough cleansing and the application of an appropriate antibacterial ointment. Tetanus prophylaxis should be administered as usual, and the patient should be instructed to recleanse the area in 24 hours, reapply an antibacterial ointment, and return for a wound check in 48 hours if evidence of infection occurs.
More Significant Injuries
The treatment of more significant injuries depends on location.
Face
Cosmetically significant lacerations involving the face occurring as a result of human bites should be thoroughly cleansed, copiously irrigated, and debrided if necessary and will thereafter usually be primarily closed; plastic surgical consultation is often sought in these injuries. Antitetanus prophylaxis should be administered as needed, and antibiotic coverage initiated as outlined in Table 57.1. A wound check in 24 to 48 hours is recommended. Puncture wounds are best treated with thorough cleansing, irrigation, if possible, and a prophylactic antibiotic; patients should be instructed to open the lesion four to six times per day for the first few days, express any purulent or bloody material, and apply a warm, moist compress for 20 to 30 minutes.
Distal Extremity and Tendon
Lacerations involving the distal extremity, particularly the hand or fingers, resulting from human bites should not be closed; subspecialty consultation and treatment are
often recommended. This is particularly important when injuries are extensive or occur in close proximity to joints, where delayed closure may result in prolonged disability and contracture related to scar formation. In other less serious injuries, a thorough cleansing, copious irrigation, debridement if needed, the institution of antibiotic therapy as outlined in “Antibiotic Therapy,” p. 524, and a wound check in 12 to 24 hours will be elected; delayed closure by the plastic or hand surgeon is typically elected. Tendon lacerations resulting from human bites will typically also be repaired by the consulting subspecialist, often after evaluation of the wound in the OR; this is also the case in patients with foreign material (teeth) and/or fractures involving the hand. Puncture wounds should not be closed.
often recommended. This is particularly important when injuries are extensive or occur in close proximity to joints, where delayed closure may result in prolonged disability and contracture related to scar formation. In other less serious injuries, a thorough cleansing, copious irrigation, debridement if needed, the institution of antibiotic therapy as outlined in “Antibiotic Therapy,” p. 524, and a wound check in 12 to 24 hours will be elected; delayed closure by the plastic or hand surgeon is typically elected. Tendon lacerations resulting from human bites will typically also be repaired by the consulting subspecialist, often after evaluation of the wound in the OR; this is also the case in patients with foreign material (teeth) and/or fractures involving the hand. Puncture wounds should not be closed.
Other
Lacerations or deep puncture wounds resulting from human bites that are not cosmetically significant and do not involve the distal extremity or tendons should be cleansed, irrigated, debrided as necessary, and reexamined in 24 to 48 hours; primary closure is not recommended. Antibiotic coverage should be provided as noted in “Antibiotic Therapy.” Consideration can be given to delayed primary closure after the initiation of antibiotics and appropriate wound care.
NONHUMAN MAMMALIAN BITES
General Considerations
Injuries occurring as a result of nonhuman mammalian bites may cause abrasions, puncture wounds, major lacerations and avulsions, or occasionally crushing injuries. Rabies prophylaxis should be a consideration in all such injuries and is discussed in “Rabies,” p. 526; antibiotic therapy is discussed in “Antibiotic Therapy,” p. 526. See Table 57-1 for animals and organisms.
Superficial abrasions should be treated routinely with thorough cleansing and the application of an appropriate antibiotic ointment. Antitetanus prophylaxis should be administered if needed.
