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Tox study > Envenomation > Flashcards

Envenomation Flashcards

1
Q

Where do Australian snakes rank in venomousness

A

The most venomous in the world

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2
Q

What features would warrant immediate antivenom before any labs etc post a snake bite?

A
  • Collapse/haemodynamic instability
  • Evidence of VICC/uncontrollable bleeding
  • Neurologically compromised
  • Significant GI upset (suggesting envenomation)
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3
Q

What is DIC called when caused by a snake bite?

A

Venom-induced consumptive coagulopathy

Prothrombin activators in venom cause consumption of factors V and VIII

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4
Q

Which snakes cause VICC?

A

Taipan
Brown
Tiger

+ rough scaled snakes

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5
Q

How is pressure bandage immobilisation performed?

A
  • Start distal to proximal
  • Dont cut off blood supply, should be able to just slip a finger under the bandage
  • Immobilise limb afterwards, if in the bush use a stick etc, in hospital use POP
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6
Q

How does VICC appear on coags?

A
  • undetectable fibrinogen
  • INR >3, usually above max range
  • D-Dimer massively elevated
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7
Q

What should be taken into consideration when choosing antivenom mono vs poly?

A
  • Geography (if in region with different snakes use polyvalent)
  • Clinical syndrome (including blood tests and examination
  • +/- results of VDK test
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8
Q

What are the side effects of antivenom?

A

Acute anaphylaxis
Serum sickness
Very very low risk of blood borne infection transmission

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9
Q

What are the 4 main clinical manifestations of snake venom?

A

Coagulopathy
- Mostly VICC
- black snake does anticoagulant effect which is mild

Neurotoxicity
- Irreversible pre-synaptic vs reversible post synaptic
- Death adder, sea snake, taipan
- rarer and slower in tiger/brown

Rhabdomyolysis
- Tiger, taipan, sea snake

Microangiopathic haemolytic anaemia (MAHA)
- Brown, tiger, taipan

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10
Q

What are the 6 main classes of snake in Australia?

A

Brown
Tiger
Taipan
Sea snake
Death adder
Black snake

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11
Q

What is the purpose of the SVDK snake venom testing kit?

A

Does NOT determine if someone needs antivenom (clinic + labs)

Helps determine which type of monovalent venom to give, instead of just giving everyone polyvalent

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12
Q

Which Australian state doesn’t stock polyvalent antivenom?

A

Tasmania
Only venomous snake is the tiger snake so only has tiger snake antivenom

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13
Q

What are the typical issues and treatment for blue ringed octopus envenomation?

A
  • Hapalochlaena lunulata and maculosa
  • Produces a life threatening descending flaccid paralysis
  • Respiratory failure and also hypotension can occur

No specific antivenom, treatment is supportive

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14
Q

What is Irukandji Syndrome and what causes it?

A
  • Causes by Carukia barnesi
  • Acts by producing a massive catecholamine surge
  • Usually not painful and no to minimal outward signs when stung
  • When symptoms begin can develop extreme pain needing +++ opioids
  • Symptoms start 30-120mins post sting and resolve within 12hrs
  • Severe symptoms usually present within 12 hrs

Issues all related to catecholamine release including APO, hypertensive crisis, AMI, cardiogenic shock and intracranial bleeds (also get impending sense of doom)

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15
Q

What is the treatment for Irukandji syndrome?

A
  • Poor vinegar on sting sites to inactivate all undischarged nematocysts
  • Do NOT place a PIB
  • IV high dose opioids for pain and hypertension
  • IV Magnesium 10mmol for refractory pain
  • IV GTN infusion for hypertension
  • May require intubation
  • There is no antivenom
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16
Q

How does the redback spider envenomation usually present?

A
  • Latrodectus hasselti
  • Causes Latrodectosus (as do all black widow spiders)
  • usually found in temperate regions is SA, Vic, NSW
  • Unlikely Northern Aus or tasmania
  • Significant pain at the bite site that radiates proximally
  • Sometimes causes erection in paediatrics

Redback spider does have an antivenom but only used for significant refractory symptoms

17
Q

How does Box Jellyfish envenomation usually present?

A

Basics
- Chironex Fleckieri and Carukia barnesi
- Extremely painful stings with noticeable linear welts in a crosshatched pattern
- Pain usually last up to 8hrs
- Toxin disrupts Na+/Ca+ channels, can cause direct cardiac toxicity
- Cardiac compromise and arrhythmias are the main issues beyond pain
- Northern Aus Nov-April

Treatment
- Box jellyfish antidote is available
- cardiac arrest (6 ampules), severe envenoming (3 ampules), refractory pain (1 ampule)
- PBI is contraindicated
- Vinegar topically is indicated to inactivate undischarged nematodes
- IV magnesium can be considered for refractory cases
- Topical ice can help

18
Q

How does tick envenomation present?

A

Tick paralysis
- a symmetric ascending paralysis similar to Guillane-Barre syndrome
- Can occur up to 3days post tick removal
- Can last for weeks
- No specific antidote/venom, supportive treatment until paralysis resolves

19
Q

What needs to be satisfied to take down a PBI post snake bite?

A
  • Patient stable/asymptomatic
  • No clinical/biochemical evidence of envenomation
20
Q

What is the difference between the paralysis caused by tick bites and snake bites?

A
21
Q

What are the basic features of tick bites in Australia?

A

Basics
- Most important is paralysis tick Ixodes holocyclus
- Usually found east coast from winter to the start of summer
- The likelihood of complications increases with length of tick attachment (particularly >7days)
- Children more susceptible to complications

Complications
- Ascending paralysis
- Tick typhus (Rickettsiae, fevers, rash, malaise, muscle aches, lymph nodes)
- Allergy ie anaphylaxis
- Meat allergy syndrome

22
Q

How should ticks be treated?

A

Tick-Off freezing spray
- Freezes tick rapidly, then falls off within 20mins or so
- Contraindicated in sensitive areas (ie face), diabetes/PVD, haemophilia and sensitivity to cold

If contraindicated then may need surgical excision in hospital

Using other methods may cause the tick to rapidly inject large amounts of venom that can increase risk of complications, particulalry anaphylaxis

23
Q

Which of the most venomous animals in the world does australia have?

A

Western Taipan
- Oxyuranus microlepidotus

Box Jellyfish
- chironex fleckieri

Stone fish
- Synanceia verrucosa

Funnel Web Spider
- Atrax robustus

Blue ringed octopus
- Hapalochlaena lunulata

24
Q

What are the specific examination findings that should be looked for with snake bite?

A

Neuro
- Diplopia, ptosis
- weakness, AMS

Haem
- Bleeding from bite site or cannulas

CVS
- initial collapse, shock, arrest

Other
- Muscle tenderness, sweating, nausea, vomiting

25
Q

What are the specific blood tests for snake bites and their derangments?

A

INR >1.2 (usually massive)
Prolonged APTT
Low/undetectable Fibrinogen
D-Dimer at least 10x normal
CK >1000
AKI with raised creatinine
MAHA
- anaemia, thrombocytopaenia, spherocytes, raised LDH

26
Q

How does Funnel web spider envenomation present?

A

Basics
- Any big black spider QLD/NSW
- Atrax robustus
- Severely painful bite with obvious fang marks
- Systemic envenomation within 30mins

Toxin effects
- Potent neurotoxin that block Na+ channels and produces cholinergic + adrenergic stimulation
- Increase autonomic activity and neuromuscular excitation

MX
- PIB indicated
- 4 ampules antivenom in cardiac arrest
- 2 ampules for symptoms
- If no evidence

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