Australian Spider Bites. Dr Sanj Fernando

Transcription

1 Australian Spider Bites Dr Sanj Fernando

2

3 Funnel Web Spider Atrax robustus

4 Funnel-Web Spider details Large spider - usually seen fangs (4mm long) can penetrate a nail aggressive - bites repeatedly venom from smaller male spider is five times as toxic than the female (all deaths from male spider bites)

5 Funnel-Web Habitat Distribution: around Sydney Newcastle to Nowra (Brisbane,Lithgow) ground dwellers

6 Funnel-Web venom Most bites (9/10) do not result in envenomation Single bite potentially fatal Atratoxin release Ach, adrenaline, noradrenaline Ca2+, 5HT receptor antagonist produces autonomic storm 2-4hrs later - neurotransmitter depletion = weakness

7 Hadronyche species (Tree funnel web) Widely distributed as toxic as Sydney Funnel-web similar symptoms responds to Funnel-Web antivenin

8 Funnel-Web spider bite Immediate pain local erythema

9 Funnel-Web spider envenomation 10min to systemic envenomation BP - hypo initially -> severe hypertension APO (occurs in 30% - a/w mortality) hyperthermia piloerection, sweating vomiting muscle spasms and fasiculations (facial and intercostal initially) confusion, coma (increased ICP) death can occur in the first hour

10 Funnel-Web Spider bite Management First aid pressure immobilisation should remain until in hospital IV access antivenin available

11 Funnel-Web Spider bite Management - Pressure immobilisation

12 Funnel-Web Spider bite Management - Pressure immobilisation Developed 1978 aim is to retard venom distribution via lymphatics broad bandage to entire limb can bandage over clothes include toes/ fingers to stop movement not so tight to occlude circulation (sprained ankle) splint limb

13 Funnel-Web Spider bite Management - Pressure immobilisation Pressure-immobilisation is recommended for: All Australian venomous snake bites, including sea snake bites Funnel web spider bites Box jellyfish stings (if possible) Bee, wasp and ant stings in allergic individuals Blue ringed octopus bites Cone snail (cone shell) stings Australian paralysis tick envenomation

14 Funnel-Web Spider bite Management - Pressure immobilisation Do not use pressure-immobilisation first aid for: Redback Spider bites Other spider bites, including mouse spiders, white tailed spiders Bluebottle jellyfish stings Other jellyfish stings Stonefish and other fish stings Bee and wasp stings in non-allergic individuals Bites or stings by scorpions, centipedes, beetles

15 Funnel-Web Spider bite Management - Antivenin Purified rabbit IgG ($490) low incidence of allergy indications muscle fasiculations (tongue, lips may be earliest) salivation, lacrimation piloerection tachycardia, hypertension dyspnoea (APO) altered mental state (increased ICP)

16 Funnel-Web Spider bite Management - Antivenin Pressure immobilisation must not be removed before IV access appropriate monitoring BP ECG SpO2 pre med - steroids - not mandatory as allergy rare

17 Funnel-Web Spider bite Management - Antivenin 5mls/amp - standard dose = 2amp (10mls) slow IV rpt 15min if no improvement (20 amps have been necessary) most will remain asymptomatic

18 Funnel-Web Spider bite Management - Supportive Mx Airway control atropine alpha/beta blockers antiemetics fluid resuscitation (careful balance) ADT may need mechanical ventilation

19 Funnel-Web Spider bite Management - Disposition May be discharged after 4/24 if spider identified and no symptoms without treatment admit if antivenin used +/- ICU

20 Red Back Spider

21 Red Back Spider Latrodectus mactans hasselti

22 Red Back Spider - details Female has red stripe and is dangerous Fangs of male are smaller and not harmful non aggressive nature prolific breeders 20% of bites result in systemic envenomation most bites in summer Extremities (genitalia) mostly bitten

23 Red Back Spider - habitat distributed throughout Australia prefers dry sheltered areas - sheds, outdoor areas daddy long legs, and white tailed spiders kill red back spiders

24 Red Back Spider - venom Release of Ach and catecholamines at autonomic synapses and neuromuscular junctions deaths prior to introduction of antivenin in 1956 Commonest bite requiring antivenin in Australia

25 Red Back Spider Local sympt. Initial bite may go undetected Bite site may be unremarkable Pain within minutes increasing intensity Erythema Lymph nodes painful within 30 min Piloerection around bite site Sweating may be profuse Often localised May involve whole limb or distant site

26 Red Back Spider Local sympt.

27 Red Back Spider Local sympt. Geoffrey K Isbister and Michael R Gray Diagnostic utility of circumstances and early clinical effects of spider bites in differentiating bites by redback spiders, L. hasselti (68 cases), from all other types of biting spiders in Australia* MJA 2003; 179 (2): Most specific features of presentation: Mechanism putting on shoes 95%spec,28%sens Local features Increasing pain over the first hour- 98% spec, 54% sens Diaphoresis (local and regional)-94%spec, 34%sens Radiating pain -96%spec, 38%sens Severe pain 75%spec, 62%sens

28 Red Back Spider Systemic sympt. Envenomation = latrodectism N,V,D,abdo pain Headache Migratory arthralgia Fever Restlessness, tremor H/T Muscle cramps, spasms Patchy paralysis Severe envenomation usually > 3hrs to develop and debilitating sympt. May last months

29 Red Back Spider Differential Commonly mistaken for other disease as bite often not noticed Has been mistaken for Sepsis Acute hepatitis Testicular torsion Acute abdo No Investigation helpful

30 Red Back Spider Management No pressure immobilisation Slow symptom progression Worsens pain ICE (unproven) Pain Mx if does not respond to paracetamol/narcotics needs antivenom Sedatives muscle spasms ADT

31 Red Back Spider Antivenin Indications: Pain Latrodectism Atypical clinical findings but Hx suggestive Allergy rate =0.5% -premedication usually not required (Hx horse allergy or prior exposure to equine immunoglobulin at risk of allergy/anaphy) Serum sickness = 1.4% - steroids post treatment not usually required No change in dose for children or pregnant women May be effective weeks after bite

32

33 Red Back Spider Antivenin Controversies IV vs IM administration Biers block

34 Red Back Spider Disposition If asymptomatic after 1 hr with or without antivenom : Discharge home Period of surveillance 24 hrs (delayed sympt) Advise to return if symptoms return If ongoing symptoms or Dx unclear : Admit and observe 24 hrs

35 Brown House spider (cupboard spider)

36 Brown House spider Distributed throughout Australia Appear similar to Red Back but may have yellow, red or whit spots (never a stripe) Local reaction & Envenomation is similar to Red Back but less severe Red Back antivenin has been used to treat envenomation

37 Huntsman spider

38 Huntsman spider Habitat houses, cars (enter houses at night searching for insects) Non aggressive Large Bite: local erythema and mild pain Rarely sweating, nausea and vomiting

39 Mouse spider

40 Mouse spider East costal and highland Burrows in the ground with trapdoors Not aggressive Highly venomous Similar presentation to funnel-web Funnel-web antivenin used successfully in one case

41 Wolf spider

42 Wolf spider Common, ground dwelling spider Local pain and swelling? Cause of necrotising arachnodism

43 White tailed spider

44 White tailed spider Habitat: inside homes Shelters in bedding, shoes, clothing Bite: Usually painful erythema?cause of necrotising arachnidism

45 Recluse spider

46 Recluse spider Habitat: Urban Shelters in clothing, bedding etc. Non aggressive unless cornered Bite: Pain in 2-3 hrs Erythema and blistering Dry ulcer 7 days Most likely cause of necrotising arachnidism Methaemaglobineamia (rare)

47 Quiz spider identification

48 Female funnel-web

49 ?

50 Huntsman

51 ?

52 Red Back spider

53 ?

54 Male Mouse spider

55 ?

56 Wolf spider

57 ?

58 Female mouse spider

59 ?

60 White tailed spider