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Spiders & their toxins

Spiders & their toxins. Joe Alcock MD MS Emergency Medicine, NM VAMC UNM Dept Emergency Medicine. 21 year old woman in Sydney. Cleaning out swimming pool trap Feels a sharp pain in her right hand Develops nausea, paresthesias, sweats. Sydney Funnel Web Spider. Funnel Web Spider.

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Spiders & their toxins

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  1. Spiders & their toxins Joe Alcock MD MS Emergency Medicine, NM VAMC UNM Dept Emergency Medicine

  2. 21 year old woman in Sydney • Cleaning out swimming pool trap • Feels a sharp pain in her right hand • Develops nausea, paresthesias, sweats

  3. Sydney Funnel Web Spider

  4. Funnel Web Spider • Australasian funnel-web spiders • Suborder Mygalomorphae - includes tarantulas • Family Hexathelidae • Sydney f.w.s Atrax robustus • Chelicerae (fangs) contain venom apparatus • 2 genera in Australia: Atrax, Hadronyche

  5. Range & habitat • Eastern coast of Australia • Fws also found in New Guinea & Solomon Islands • Spiders construct a funnel shaped web and wait for prey to fall in. • Funnels constructed near rocks, logs • Diet consists of insects and small vertebrates

  6. Scope of problem • 77 severe envenomations between 1999 and 2003 • Deaths only recorded from Atrax robustus • No deaths since introduction of antivenom

  7. Toxicity • 77 severe cases 1999 - 2003 • Male spiders cause most bites • 10-25% bites produce toxicity • Spiders measure 5 cm, fangs can penetrate fingernails • Delta-Atracotoxins • Presynaptic neurotoxins - open sodium channels - inducing action potentials • Autonomic storm - endogenous Ach norepinephrine & epinephrine.

  8. Envenomation • Painful Bite - acidic pH, large size of fangs • Onset rapid - median 28 min, 2 cases after 2 hours (pressure dressing) • Early symptoms: periorbital paresthesias, facial muscle twitching, vomiting, diaphoresis, salivation, dyspnea • Agitation, confusion, coma, hypertension, metabolic acidosis, mydriasis, fasciculations • Increased ICP - death

  9. Funnel Web Treatment • Pressure immobilization bandage • Antivenom purified rabbit IgG • Developed in 1981 in Melbourne • Fast acting and effective • Hospitalization rates have changed from 14 days to 3 days on average with no deaths since its availability.

  10. First Aid • Keep victim calm and still if possible • Immobilize the bitten area and keep it lower than the heart. Remove rings. • Pressure dressing - NOT tourniquet • Get patient to definitive care - antivenin - Sooner the better!

  11. Other Australian Mygalomorph spiders • Mouse Spider - local pain, local paresthesias • Trap door spider - minor effects only

  12. 60 yo m collecting yard waste next to house • Feels a sharp bite on forearm • Noticed a medium sized spider with prominent abdomen • Red spot on underside of abdomen • Hourglass shaped • Should he worry?

  13. Latrodectus

  14. History • Slight initial pain: pinch or pinprick • In 1 hour, systemic symptoms begin and may last for a few days. • Muscle cramping - local and large muscle groups - abdomen, back, thighs. • Nausea and vomiting • Headache • Anxiety

  15. Physical • Abnormal vital signs, Hypertension, Tachycardia • Diaphoresis: local or remote from site of envenomation • Tiny fang marks may be visible • Bite appearance: small circle of redness, swelling around immediate bite site. May have blanching with red border

  16. Bite after 1 hour

  17. Physical Exam - continued • Abdominal rigidity - acute abdomen. • Neurotoxic effects, weakness, fasciculations, and ptosis • Latrodectus facies, with facial muscle spasm of, edematous eyelids, & lacrimation. Mimics an allergic reaction.

  18. Grading Bites • Grade 1 - Mild envenomation, Localized pain at bitesite, Normal vitals • Grade 2 - Moderate envenomation: Muscle pain in the bitten arm or leg Muscle pain may extend to abdomen if bitten on leg, or to the chest with bite on arm. Local diaphoresis of envenomation site or involved extremity Normal vital signs

  19. Grade 3 Latrodectism • Severe envenomation Generalized muscular pain in the back, abdomen, and chest Diaphoresis remote from envenomation site Abnormal vital signs (blood pressure >140/90 mm Hg, pulse >100)Nausea and vomiting Headache

  20. Antivenin • Antivenin Latrodectus mactans - horse serum (Merck product) • Consider for patients with grade 2 or grade 3 envenomations in whom narcotics do not control pain and are low risk for allergic reactions • Rec for certain patient groups, such as children and elderly persons • skin testing for possible allergic reaction to the antivenom.

  21. Antivenin Precautions • Mortality from widow spider envenomation is extremely rare, and some argue against administration of antivenom when treatment may be more dangerous than the injury • some recommend routine premedication with antihistamines (H1 and H2 blockers) • black widow spider envenomation is associated with abruptio placentae and fetal demise; benefits of antivenom administration in pregnancy must be weighed against risks

  22. The dreaded brown recluse • Necrotic skin ulceration • Spiders get a bad rap - blamed for every little skin infection, folliculitis

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