What is the diagnosis breakdown for envenomation and puncture wounds resulting from stings and bites, including key points for the National Board of Medical Examiners (NBME) Family Medicine Shelf and United States Medical Licensing Examination (USMLE) Step 2?

From the Guidelines

Sting and bite injuries require prompt assessment and management based on the specific organism involved, with a focus on preventing morbidity, mortality, and improving quality of life. For insect stings (bees, wasps, hornets), remove the stinger if present, clean the area, and apply cold compresses, as most reactions are local, but anaphylaxis requires immediate epinephrine (0.3-0.5mg IM for adults, 0.15mg for children) 1.

Key Considerations

• For spider bites, black widow bites cause severe muscle pain and cramping treated with IV calcium gluconate and benzodiazepines, while brown recluse bites cause necrotic lesions requiring wound care and possibly dapsone.
• Scorpion stings may cause severe pain and neurotoxicity, managed with pain control and supportive care, including the use of topical 5% lidocaine, administration of intravenous acetaminophen, or topical application of ice, as supported by recent guidelines 1.
• Snake bites, particularly from pit vipers, require immobilization of the affected limb, removal of constrictive items, and prompt administration of antivenom (CroFab for North American pit vipers) if indicated.
• Marine envenomations from jellyfish or stingrays should be treated by removing nematocysts (with vinegar for jellyfish), immersing in hot water (for stingrays), and providing pain management.
• Mammal bites, especially from cats and dogs, have high infection risk requiring thorough irrigation, debridement, and prophylactic antibiotics (amoxicillin-clavulanate 875/125mg BID for 5-7 days).
• Human bites should be treated with amoxicillin-clavulanate or alternatives like clindamycin plus fluoroquinolone for penicillin-allergic patients.
• Rabies post-exposure prophylaxis with rabies immune globulin and vaccine series is essential for bites from potentially rabid animals.
• Tetanus prophylaxis should be considered for all wounds based on immunization status.

Management of Acute Reactions

• Acute systemic reactions to insect stings should be treated like any anaphylactic reaction, with epinephrine injection, supportive therapy, and transport to an emergency department 1.
• In patients with a history of only cutaneous systemic reactions, initial treatment of cutaneous systemic symptoms might include antihistamines and close observation.
• Fatal sting reactions have been associated with delay in administration of epinephrine.
• Treatment of large local reactions can include antihistamines, cold compresses, and in severe cases a brief course of oral corticosteroids, with antibiotics usually not necessary 1.

From the FDA Drug Label

1 INDICATIONS & USAGE Adrenalin® is available as a single-use 1 mL vial and a multiple-use 30 mL vial for intramuscular and subcutaneous use. Emergency treatment of allergic reactions (Type I), including anaphylaxis, which may result from allergic reactions to insect stings, biting insects, foods, drugs, sera, diagnostic testing substances and other allergens, as well as idiopathic anaphylaxis or exercise-induced anaphylaxis.

The signs and symptoms associated with anaphylaxis include flushing, apprehension, syncope, tachycardia, thready or unobtainable pulse associated with hypotension, convulsions, vomiting, diarrhea and abdominal cramps, involuntary voiding, airway swelling, laryngospasm, bronchospasm, pruritus, urticaria or angioedema, swelling of the eyelids, lips, and tongue.

Diagnosis Breakdown for Sting and Bite Injuries:

• Anaphylaxis: a severe, life-threatening allergic reaction that can occur within minutes of a sting or bite, characterized by symptoms such as flushing, apprehension, syncope, tachycardia, and hypotension.
• Key symptoms to look out for:
  • Airway swelling
  • Laryngospasm
  • Bronchospasm
  • Pruritus
  • Urticaria or angioedema
  • Swelling of the eyelids, lips, and tongue
• Treatment: epinephrine (IM) is the first-line treatment for anaphylaxis, and should be administered promptly in the event of a severe allergic reaction.
• Important considerations for NBME Family Medicine Shelf and Step 2:
  • Recognize the signs and symptoms of anaphylaxis and administer epinephrine promptly.
  • Be aware of the potential risks and complications of epinephrine administration, including cardiac arrhythmias and tissue necrosis 2.
  • Consider the patient's medical history and current medications when administering epinephrine, as certain conditions (such as heart disease) may increase the risk of adverse reactions 2.

From the Research

Diagnosis Breakdown for Sting and Bite Injuries

• Anaphylaxis Recognition: Anaphylaxis is a life-threatening systemic reaction that can occur within one to two hours of exposure to an allergen, with symptoms including urticaria, difficulty breathing, and mucosal swelling 3.
• Common Triggers: The most common triggers for anaphylaxis are medications, stinging insect venoms, and foods, although unidentified triggers can occur in up to one-fifth of cases 3.
• Treatment: Intramuscular epinephrine is the immediate treatment for anaphylaxis, with intravenous epinephrine used in patients in shock, along with fluid resuscitation and airway management as needed 4, 5.
• Biphasic Reactions: Patients should be monitored for potential biphasic reactions, which can occur four to 12 hours after the initial reaction, depending on risk factors for severe anaphylaxis 3.
• Insect Sting Allergy: Insect sting allergy can cause systemic allergic reactions, which may be potentially life-threatening in about 10% of cases, with symptoms ranging from urticaria and edema to respiratory and cardiovascular symptoms 6.
• Venom Immunotherapy: Venom immunotherapy is effective in 80% to 100% of individuals treated for 3 to 5 years, although certain groups may require a twice higher maintenance dose 6.
• Epinephrine Administration: Epinephrine is the drug of choice for anaphylaxis, with properly administered epinephrine having no absolute contraindication in this clinical setting, and should be administered promptly and in appropriate doses 5.

Key Pearls for NBME Family Medicine Shelf and Step 2

• Early Epinephrine Administration: Early administration of intramuscular epinephrine is crucial in the treatment of anaphylaxis 4, 3, 5.
• Airway Management: Airway obstruction must be recognized and managed promptly, with early intubation may be necessary in severe cases 4.
• Biphasic Reaction Monitoring: Patients should be monitored for potential biphasic reactions, which can occur four to 12 hours after the initial reaction 3.
• Venom Immunotherapy: Venom immunotherapy is an effective treatment for insect sting allergy, although certain groups may require a twice higher maintenance dose 6.