EMET 2015 Objectives Review current management of medically important snake bites in Southern Illawarra Review management of funnel web bite Review management of Redback envenomation Snake bites ID: 759090
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Slide1
Snake and Spider envenomation
EMET 2015
Slide2Objectives
Review current management of medically important snake bites in Southern
Illawarra
Review management of funnel web bite
Review management of
Redback
envenomation
Slide3Snake bites
Bites uncommonSevere envenoming rareDeaths 1-4/yr AustraliaOccur in warmer months in regional/rural areas
Slide4Species
Brown snake commonest and most dangerousTiger snakeRed-bellied black snake
Slide5Clinical features
Majority bites ‘dry’May be trivial bite marksUsually no local effects from Brown snakeMild local bruising & pain with Tiger + Black
Slide6Initial management
Immobilise & Pressure bandageIV access & analgesiaCollect pathology & swabAssess for envenomationArrange transfer if req.
Slide7Envenomation syndromes
Slide8Initial laboratory assessment
FBCUECCKINR, aPTTFibrinogen D-DimerDO NOT use PoC D-dimer, INR machines
Slide9No envenomation
No clinical signs envenomation
Initial pathology N
Remove PIB
Observe 1
hr
Repeat pathology + neurological exam to exclude envenomation
Repeat testing 6 +12
hrs
post bite
Asymptomatic - discharge during day
Slide10Envenomated?
Hx collapse = brown snake and certain envenomationVICC rapidly evident within 1-2 hrsNeurotoxicity = ptosis and descending paralysisEarly antivenom reduces severity of these effects
Slide11Antivenom selection and use
Based on syndrome and geographyMore accurate than SVDK1 ampoule sufficient for treatment of biteIf identification uncertain, 1 ampoule brown & tiger may be given to cover probable species
Slide12Antivenom use
20% chance of cutaneous reaction<5% chance anaphylaxis33% chance serum sickness reaction 4-14 days later
Slide13VICC management
Median time to recovery of INR<2 ~ 15
hrs
FFP ?
C
ontroversial – more effective >6
hrs
from bite
Shortens time to recovery INR, but not discharge
PCC not effective (Factor V, VIII)
If active major bleeding
T
oxicology input
Most have benign course, d/c in 24-48
hrs
Watch for rising
creatinine
,
thrombocytopaenia
thrombotic
microangiopathy
Slide14Other syndromes
RhabomyolysisTreated as per standard therapyNeurotoxicityRequires ongoing observation;May be slowly progressive and require ventilatory support in worst cases
Slide15Funnel-Web Spider
Slide16Facts
Arguably most dangerous spider on the planetVenom only affects primates!Range from South Coast to NewcastleMale spider greater threat warmer months
Slide17Clinical features
Noticeable bite!‘Big black spider’Majority dry bitesSymptom onset usually within 1-2 hrs. Observe for 4 hrs for symptomsNeurotoxin – autonomic storm
Slide18Clinical features
Slide19Treatment
Rapid recognition vitalPIB if pre-hospital; remain in place until antivenom given2 ampoules IV. Repeat up to 8 ampoules as requiredSedation/atropine/PEEP may be needed in severe casesOnce symptoms resolve, can discharge after observation during daylight hrs
Slide20Redback spider
Slide21Redback spider
Australian icon!Widow spider ‘Lactrodectism’Bites from the female spiderFound around outside household
Slide22Lactrodectism
Bite not always noted initiallyCharacteristic severe spreading regional pain May involve abdomen or chestPathognomonic bite signs – erythema and localised piloerection
Slide23Management
Indication for treatment = painOften not amenable to simple analgesiaHistorically recommended – 2 x ampoules Redback antivenom IM
Slide24Recent trials
RAVE 2008 - compared IV to IM antivenomNo difference in outcomesSubsequent substudy showed no detectable antivenom in bloodstream after IM administration
Dart et al 2013 – Compared Black widow
antivenom
to placebo
Small trial;
However, no significant differences in outcomes of pain at 150mins.
Trend towards faster resolution at 30
mins
– not significant
Slide25RAVE II
Australian
randomised
, placebo controlled trial of
R
edback
antivenom
224 patients (112 per arm)
Compared pain relief at 2
hrs
and relief of systemic symptoms
Both arms treated with
paracetamol
, ibuprofen and oxycodone prior to
randomisation
No significant differences in pain scores at 2, 4 or 24
hrs
Non-significant improvement at 2
hrs
34%
vs
24 % in AV group, not sustained
No difference in relief of systemic symptoms
Slide26Recommendations
Oral analgesia no worse than
antivenom
Risk of reaction needs to be very carefully balanced against dubious analgesic benefit
NNT = ?10 for earlier relief?
vs
NNH = 25-50 for anaphylaxis
Currently no good evidence-based analgesic treatment for
Redback
bite
Slide27White-tip(tail) Spider
Much maligned spider in Australian culture Previously ‘implicated’ as ‘cause’ of necrotic arachnidism in AustraliaDue to very poor research case series in 70’sMany doubts as to whether necrotic arachnidism is even a valid disease entity in Aust.White tip spiders NOT responsible for necrotic arachnidism or necrotising fasciitisSuspected ‘white –tip bite’ – 1)Was spider actually seen to bite?; if not, suspect other cause of any apparent skin lesion (eg cMRSA)2) If definite spider bite, does NOT need antibiotics; treat as for generic insect bite
Slide28Questions?
Slide29Summary
Become familiar with local snake sp. envenomation syndromes to predict choice of
antivenom
– more accurate than SVDK
Need 1 ampoule of
antivenom
only for envenomation
FFP for VICC controversial and probably ineffective early
Funnelweb
bites – observe 4
hrs
; if no symptoms, may discharge
Redback
antivenom
not as effective as everyone thought !