Bites

1. Bites Chapters 194

2. Hymenoptera (wasps, bees, & ants) • Local Reaction • Urticarial lesion contiguous with the sting site • Toxic Reaction • Systemic: n/v/d, syncope, edema, muscle spasms • Anaphylactic Reaction • Airway obstruction & hypotension usu. within first hour • IgE-mediated • Delayed Reaction • 5-14 days later, symptoms of serum sickness • Unusual Reaction • Neurologic, cardiovascular, and urologic symptoms

3. Treatment of Stings • Remove stinger • Wash with soap and water • Ice packs • Oral antihistamines and NSAIDS • Elevation and rest

4. Treatment of anaphylaxis • B-agonist nebulizers • Massive crystalloid infusion for hypotension • If hypotension is persistent then dopamine • Steroids: solumedrol 125mg • Benadryl 25-50mg PO/IM/IV • H2-blocker IV • Epinephrine given IM • 0.3- 0.5mg of 1:1000 in adults • 0.1mg/kg in children; never more than 0.3mg

5. Preventative Care • “Every patient who has had a systemic reaction should be provided with an insect sting kit containing premeasured epinephrine and be carefully instructed in its use. The physician should stress that the patient must inject the epinephrine at the first sign of a systemic reaction.” Tintinalli • Medic Alert bracelet/tags

6. Fire Ants • Gulf Coast states • Tendency to swarm • Results in several stings and even death • Sting • Papule that becomes a sterile pustule in 6-24hrs • Localized necrosis, scarring, and secondary infection

7. Spiders (Araneae)Necrotic Arachnidism (Loxosceles) • True brown recluse • Corner spider • Arizona brown spider

8. Clinical presentation of Loxosceles • Initially painless • Most commonly: • erythematous lesion that becomes firm and heals in several days • Occasionally(24hrs-4days) • Erythema-blister-bluish discoloration -necrosis-eschar • Systemic effects rare (24-72hrs): • n/v, chills, arthralgias, hemolysis, thrombocytopenia, hemoglobinuria, and renal failure • DIC

9. Treatment of the loxosceles • Antibiotics if signs of infection • Analgesia • If necrotic, surgical debridement • New developments in: • Hyperbaric O2, cyproheptadine, dapsone, steroids, and topical nitroglycerin

10. Hobo spider (Tegenariaagrestis) • Pacific Northwest and Canada • Similar envenomations to brown recluse • Delayed presentation • May not heal for up to 45 days • No specific antidote

11. Widow spider (Latrodectus) • Worldwide distribution • Black widow is best known • Most commonly bite btw April and October

12. Clinical presentation • Pinprick followed by intense pain that spreads • Erythema in 20-60mins • 1/3 develop target lesion • Muscle cramp-like spams of large muscle groups Severe abdominal pain mimicking a surgical abdomen (board question) 60% develop htn, nausea, diarrhea, h/a, photophobia

13. Treatment • Antivenom • Liberal use of opiods and benzos • Treat anaphylaxis if present

14. Armed spiders (Phoneutria) • South America • Usually no significan symptoms • Some have sympathetic, parasympathetic and spinal cord impairment • Treat supportively

15. Funnel-Web Spiders (Atrax/hadronyche) • Australia and near-by islands • Neurotoxic effects with death from cardiac arrest and pulmonary failure • Compressive elastic bandage/immobilization • Treat with antivenom

16. Sac and Running Spiders (Cheiracanthium) • House-dwelling • South African • Local pain, swelling, erythema, with h/a, malaise, dizziness and nausea • Treat with local care

17. Tarantula • Hairs on abdomen used in defense • “flick” hairs a short distance with their back legs • Consider in those presenting with red eye and pain after handling a tarantula • Surgical removal and topical steroids • Opthalmianodosa: granulomatous, nodular reaction of the eye • Bites are painful, edematous and erythematous

18. Scorpions • Immediate pain and paresthesias at the site and spreading • Cranial n. and somatic motor dysfunction • Excessive motor activity (seizure-like)scorpion • Treat with antivenom to prevent cardiac dysfunction, pulmonary edema, pancreatitis, DIC, skin necrosis, and death

19. Ticks (ixodes, dermacentor, etc) • Obligate, bloodsucking arthropods • Disease vectors (RMSF, Lyme,tularemia) • Consider with symmetric flaccid paralysis with loss of deep tendon reflexes similar to Guillain-Barre • Remove by grasping with forceps near the point of attachment and steadily pull straight back • Lyme prevention with doxycylcine 200mg PO

20. Chiggers (Trombiculidae) • Chiggers results from mite larvae feeding on host skin cells • Intense pruritus • Severe: fever, edema, erythemamultiforme-like lesions, cellulitis • Treat with antihistamine, steroids, and antibiotics if necessary

21. Mosquitos, flies, fleas, and lice • Localized redness, wheals and itching • Treat with antihistamines and NSAIDS • Consider West Nile Virus induced encephalopathy • Consider Malaria esp if hx of travel

22. Kissing bugs and bed bugs • Bites from both painless • Differentiate by bed bug bites are linear and they leave black excrement on the sheets • Symptomatic treatment • Both are blood-suckers and have potential for disease carriers

23. Blister beetles (Coleoptera) • Contain highly potent vesicant cantharidin that extrudes from their joints if disturbed • Remove by blowing or flicking • Cause local inflammation that may lead to bullae formation • If ingested causes vomiting, hematemesis, oliguria, and renal failure • Treatment is supportive