Brown Snake Envenomation

Quick Answer

One-liner: Brown snake envenomation causes life-threatening Venom-Induced Consumption Coagulopathy (VICC) requiring urgent Brown Snake Antivenom (one vial) after pressure immobilisation.

Brown snakes (Pseudonaja species) are responsible for the majority of snakebite deaths in Australia. The venom contains a potent prothrombin activator causing VICC - complete consumption of fibrinogen, Factor V, and Factor VIII. Patients present with bite site pain, systemic symptoms, and potentially early collapse. Immediate PIB is critical. ED management involves serial coagulation testing, administration of one vial of CSL Brown Snake Antivenom (1,000 units), and admission for observation until coagulopathy resolves (typically 24-48 hours). Mortality is low with appropriate treatment but early collapse and intracranial haemorrhage remain major risks.

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ACEM Exam Focus

Primary Exam Relevance

• Pharmacology: Equine antivenom pharmacology, anaphylaxis management, antihistamine and adrenaline premedication
• Pathophysiology: VICC mechanism, prothrombin activator complex, thrombin generation, factor consumption
• Physiology: Coagulation cascade, fibrinogen synthesis (liver), D-dimer production

Fellowship Exam Relevance

• Written (SAQ): Antivenom dosing rationale, VICC management, indications for blood products
• OSCE: Resuscitation station (early collapse, antivenom administration), Communication station (explaining snakebite to anxious patient)
• Key domains tested: Medical Expert (clinical management), Communicator (patient education), Leader (retrieval coordination)

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Key Points

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Epidemiology

Australian/NZ Specific

• Geographic distribution: Eastern brown snake (P. textilis) widespread along eastern coast and inland; Western brown snake (P. nuchalis) across Western Australia, Northern Territory, South Australia; Dugite (P. affinis) in southwest Western Australia; Peninsula brown snake (P. inframacula) in northern Western Australia and Northern Territory
• Seasonality: Peak bites in warmer months (October-April), higher activity during snake breeding season (spring)
• Rural/remote: Higher incidence in rural areas, farmers, outdoor workers; delayed presentation common in remote regions
• Indigenous population: Higher exposure risk in remote communities; potential barriers to early healthcare access

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Distribution of Brown Snake Species

Pseudonaja textilis (Eastern Brown Snake)

• Distribution: Eastern Australia from Cape York Peninsula (QLD) through NSW, Victoria, South Australia, into southeast Northern Territory and southwest Western Australia
• Geographic range: Most widespread brown snake, responsible for majority of human envenomations
• Habitat: Varied habitats including grasslands, woodlands, coastal dunes, urban fringes
• Venom: Most toxic of brown snakes, potent prothrombin activator [9]

Pseudonaja nuchalis (Western Brown Snake)

• Distribution: Western Australia, Northern Territory, South Australia, Queensland, New South Wales (inland areas)
• Geographic range: Arid and semi-arid regions of inland Australia
• Habitat: Deserts, grasslands, scrublands
• Venom: Potent procoagulant, similar VICC profile to Eastern brown [10]

Pseudonaja affinis (Dugite)

• Distribution: Southwest Western Australia (Perth region, south coast)
• Geographic range: Restricted to southwest corner of WA
• Habitat: Coastal dunes, heathlands, urban areas in Perth
• Venom: Procoagulant VICC, neurotoxic potential in some populations [11]

Pseudonaja inframacula (Peninsula Brown Snake)

• Distribution: Northern Western Australia and Northern Territory (Kimberley, Top End)
• Geographic range: Tropical northern Australia
• Habitat: Woodlands, savannah, coastal areas
• Venom: Procoagulant, may have additional neurotoxic components [12]

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Pathophysiology

Mechanism

Brown snake venom contains a potent prothrombin activator complex that functions similarly to the human Factor Xa-Va complex. This activator rapidly converts prothrombin to thrombin, leading to:

1. Massive thrombin generation - Systemic activation of coagulation cascade
2. Consumption of clotting factors - Fibrinogen, Factor V, Factor VIII, Factor XIII are depleted
3. Fibrinolysis activation - Massive D-dimer production
4. Secondary fibrinogenolysis - Fibrinogen breakdown products

The venom does NOT contain significant presynaptic or postsynaptic neurotoxins (unlike taipan or tiger snake), meaning neurotoxicity is uncommon in pure brown snake envenomation.

Pathological Progression

Bite → Venom entry → Prothrombin activation → Thrombin burst
→ Factor consumption (Fibrinogen, FV, FVIII) → VICC
→ Coagulopathy (INR greater than 13, Fibrinogen undetectable) → Haemorrhage risk
→ Liver resynthesis of factors (6-12 hrs) → Recovery

Why It Matters Clinically

• Early collapse: Venom contains other components causing direct vasodilation and capillary leak, leading to hypotension within 30 minutes in 10-20% of cases
• Intracranial haemorrhage: Major cause of death, occurs due to severe coagulopathy, may develop before antivenom administration
• Thrombotic microangiopathy (TMA): Subset of patients develop microthrombi, causing acute kidney injury (AKI) and thrombocytopenia
• Recovery time limitation: Antivenom cannot reverse established coagulopathy - liver must resynthesise consumed factors (time-limited process)

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Clinical Approach

Recognition

Triggers for Suspecting Brown Snake Envenomation:

• Snakebite witnessed in Australia (particularly eastern, western, inland regions)
• Fang marks visible on limbs (most common site)
• Systemic symptoms developing within 1-6 hours
• Coagulopathy on laboratory testing

Brown Snake vs Other Australian Snakes:

Initial Assessment

Primary Survey

• A: Airway - Assess for neurotoxicity (ptosis, ophthalmoplegia, bulbar palsy). Intubate if compromised.
• B: Breathing - Respiratory rate, oxygen saturation, work of breathing. Respiratory failure in severe neurotoxicity (rare in brown snake).
• C: Circulation - Blood pressure, heart rate, capillary refill. Hypotension (early collapse) in 10-20%.
• D: Disability - GCS, pupils, cranial nerves. Assess for neurotoxicity.
• E: Exposure - Expose bite site, remove PIB carefully (only after antivenom administered and patient stable).

History

Key Questions

Red Flag Symptoms

Examination

General Inspection

• Patient appearance: distressed, anxious, diaphoretic
• Vitals: tachycardia, hypotension (early collapse), tachypnoea
• Skin: bruising at bite site, ecchymoses, petechiae (coagulopathy)

Specific Findings

Bite Site Examination:

• Location: Most commonly lower limb (75%), upper limb (20%)
• Fang marks: 1-2 puncture wounds, 5-10mm apart
• Local reaction: Pain, swelling, bruising (usually mild, brown snake venom has low local tissue toxicity)
• No necrosis: Brown snake venom does not cause tissue necrosis (unlike some vipers)

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Investigations

Immediate (Resus Bay)

VSK (Venom Snake Kit) Interpretation

The VSK uses sandwich ELISA to detect specific venom in serum:

Clinical utility: Confirms envenoming species, guides antivenom choice if snake not identified. However, treatment should not be delayed awaiting VSK result if clinical presentation is clear and patient is unstable.

Standard ED Workup

Advanced/Specialist

Point-of-Care Ultrasound

POCUS Applications:

• EFAST: Detect free fluid (intraperitoneal, intrathoracic haemorrhage)
• Cardiac: Assess cardiac function in early collapse (poor contractility from direct myocardial toxicity)
• Focal neurological deficits: Rule out other causes if present (stroke, TIA)
• Bladder: Assess for urinary retention if neurological symptoms present

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Management

Immediate Management (First 10 minutes)

1. Apply/verify PIB if not already in place (DO NOT remove until antivenom ready)
2. Insert 2 large-bore IV cannulas (14G or 16G)
3. Draw blood for VSK, INR, aPTT, fibrinogen, FBC, U&E, CK, Group and Screen
4. Monitor: ECG, SpO2, BP (arterial line if unstable), urine output (catheter)
5. Prepare antivenom and premedication (if indicated)
6. Alert senior doctor, ICU, toxicology service, retrieval (if rural/remote)
7. Prepare for potential anaphylaxis (adrenaline, airway equipment, resuscitation drugs)

Pressure Immobilisation Bandage (PIB)

ANZCOR Guideline 9.4 - Snakebite First Aid:

Apply immediately if not already done:

1. Apply broad pressure bandage over bite site (as tight as for sprained ankle)
2. Extend bandage from fingers/toes to as high up limb as possible (cover entire limb)
3. Immobilise limb with splint (splint from fingers/toes to body)
4. Keep patient still - minimise movement, call ambulance
5. Record application time - important for clinical assessment

DO NOT:

• Cut, incise, or suck the wound
• Apply tourniquet (complete arterial occlusion)
• Wash the wound (venom needed for VSK if snake unidentified)
• Remove PIB until antivenom administered and patient stable

Evidence for PIB:

• PIB slows lymphatic spread of venom (primary lymphatic transport in early phase) [13]
• Delays systemic envenoming by 4-6 hours, allowing time for transport and antivenom preparation [14]
• No increase in local tissue damage (low local toxicity of Australian elapids) [15]

Antivenom Administration

CSL Brown Snake Antivenom

Product Details:

• Source: Equine (horse) derived
• Content: 1,000 units of Fab fragments specific to Pseudonaja venom
• Volume: 5 mL vial (reconstituted)
• Indication: Brown snake (Pseudonaja species) envenoming

Dosing:

• Adults: One vial (1,000 units) intravenously initially
• Repeat dosing: One additional vial (1,000 units) only if:
  • Patient remains clinically envenomed after 1-2 hours (ongoing systemic symptoms)
  • Coagulation parameters continue to deteriorate despite first vial
  • Snake was large, bite was prolonged (multiple bites, snake attached for minutes)
• Maximum effective dose: One vial binds all circulating venom in greater than 95% of cases; more than 2 vials rarely needed

Evidence for One-Vial Dosing:

• Isbister et al. (ASP-01): One vial (1,000 units) bound all detectable venom in 94% of cases [16]
• Recovery of coagulation independent of antivenom dose after first vial [17]
• No benefit to higher doses (historical practice: up to 20 vials) [18]

Administration Technique:

1. Pre-medication (if indicated - see below)
2. Dilute antivenom in 100-200 mL normal saline
3. Administer via rapid IV infusion over 15-20 minutes
4. Monitor closely during infusion (BP, HR, SpO2, respiratory status, skin)
5. Have adrenaline (1:1,000) ready for anaphylaxis
6. Stop infusion if anaphylaxis occurs and treat immediately

Premedication Controversy:

Current ACEM/ASCEPT Recommendation:

• Consider premedication in patients with:
  • Previous reaction to equine products
  • Severe asthma
  • Known multiple drug allergies
  • Atopic history
• Premedication regimen (if given):
  • "Adrenaline 0.5 mg (1:1,000) SC (contralateral limb) - 15 minutes before antivenom"
  • Promethazine 25 mg IM (or alternative antihistamine)
  • Hydrocortisone 100 mg IV

Anaphylaxis Management (Antivenom Reaction)

Recognise anaphylaxis:

• Sudden onset (within minutes of starting infusion)
• Skin: Urticaria, flushing, angio-oedema
• Respiratory: Wheeze, stridor, dyspnoea
• Cardiovascular: Hypotension, tachycardia
• GI: Abdominal pain, vomiting, diarrhoea

Management (ABCDE approach):

A: Airway - Consider early intubation if upper airway oedema
B: Breathing - High-flow oxygen, bronchodilators if wheeze
C: Circulation:
   - ADRENALINE 0.5 mg (1:1,000) IM (anterior thigh) - Repeat q5 min if needed
   - IV fluid resuscitation (normal saline or Hartmann's) - 500-1000 mL bolus
   - IV adrenaline (1:10,000) infusion if refractory shock (rare)
D: Disability - GCS monitoring
E: Exposure - Remove PIB (after patient stabilised)

After anaphylaxis:

• Continue antivenom infusion once stabilised (if envenoming ongoing)
• Use slower infusion rate (over 30-60 minutes)
• Consider pre-treatment with antihistamine and steroids for repeat doses

Serotherapy-Related Reactions

Antivenom Efficacy Monitoring

How do we know it worked?:

• VSK: Should become negative (venom bound by antivenom) [22]
• Coagulation parameters: INR stabilises, fibrinogen begins rising at 6-12 hours
• Clinical symptoms: Systemic symptoms improve

When to give repeat antivenom:

• Clinical worsening: New bleeding, neurological symptoms, haemodynamic instability
• Coagulation deterioration: INR continues rising, fibrinogen drops further after 1 hour
• Persistent envenoming: Ongoing symptoms after 2 hours with no improvement

Ongoing Management

After first antivenom dose:

1. Monitor Vitals: BP, HR, RR, SpO2 q15-30 min for first 2 hours, then hourly
2. Serial coagulation: INR, aPTT, fibrinogen at 2h, 4h, 6h, then q6h until recovery
3. Monitor for bleeding: Observe puncture sites, gums, urine, stool
4. Manage complications: Treat bleeding, support organ systems
5. Remove PIB: After 2 hours of patient stability (no further deterioration)
6. Admit to ICU/HDU: For VICC monitoring and complication management

Blood Product Use (Controversial)

When to use FFP/Cryoprecipitate:

Blood product rationale:

• FFP (Fresh Frozen Plasma): Contains all coagulation factors (II, V, VII, IX, X, fibrinogen)
• Cryoprecipitate: Concentrated fibrinogen, Factor VIII, Factor XIII, von Willebrand factor
• Platelets: Only needed if thrombocytopenia (below 50 x 10^9/L) or active bleeding

Timing of blood products:

• Give after antivenom (otherwise consumed by circulating venom)
• Early FFP (within 6-12 hours) may slightly speed INR recovery but doesn't improve clinical outcomes [26]
• No evidence that blood products prevent haemorrhage in asymptomatic VICC

Definitive Care

ICU/HDU admission (all patients with VICC):

• Cardiac monitoring (continuous ECG)
• Invasive BP monitoring if hypotensive or early collapse
• Central venous access if multiple blood products or inotropes needed
• Urine catheter for strict fluid balance
• Neurological observation (hourly GCS, pupils)

Duration of admission:

• Minimum: 24-48 hours (until fibrinogen greater than 1.0-1.5 g/L and INR normalises)
• Longer if: TMA with AKI, intracranial haemorrhage, major bleeding complications

Specialist involvement:

• Toxicology service: All brown snake envenomations (refer via Poisons Information Centre 13 11 26)
• Haematology: For complex VICC, TMA, or refractory coagulopathy
• Nephrology: If AKI (TMA)
• Neurosurgery: If intracranial haemorrhage
• Retrieval service: If rural/remote patient needs transfer to tertiary centre

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Disposition

Admission Criteria

Mandatory admission for:

• All patients with confirmed VICC (INR greater than 13, fibrinogen undetectable)
• All patients receiving antivenom
• Patients with early collapse or hypotension
• Patients with neurotoxicity
• Patients with active bleeding
• Patients with TMA (AKI, schistocytes on blood film)

ICU/HDU Criteria

• VICC with antivenom (standard ICU observation)
• Early collapse requiring vasopressors
• Neurotoxicity with respiratory compromise
• Major bleeding requiring blood products
• AKI (creatinine greater than 150 μmol/L) with TMA
• Intracranial haemorrhage
• Need for invasive monitoring (arterial line, CVC)

Discharge Criteria

Safe discharge requires:

• Coagulation normalised: INR normal, fibrinogen ≥1.5 g/L (typically 24-48 hours)
• No bleeding: No active or recent bleeding
• Stable haemodynamics: BP, HR normal for 6+ hours
• Improved symptoms: No systemic symptoms
• Antivenom reaction resolved: No ongoing anaphylaxis or serum sickness
• Able to return: Follow-up arranged, red flags explained

Follow-up:

• GP letter: Discharge summary including antivenom dose, reactions, coagulation recovery
• Haematology review: If coagulopathy persistent beyond 48 hours or abnormal baseline
• Toxicology follow-up: Serum sickness education (symptoms 5-14 days post-antivenom)
• Tetanus: Update if bite site wounds and booster due

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Special Populations

Paediatric Considerations

Dosing differences:

• Antivenom: One vial (1,000 units) regardless of age/weight - same as adult [27]
• Blood products: Weight-based dosing (FFP 15-20 mL/kg, cryoprecipitate 1-2 pools)
• Adrenaline: 0.01 mg/kg (1:1,000) IM (max 0.5 mg)

Special considerations:

• Higher risk of early collapse due to smaller blood volume
• Intracranial haemorrhage risk higher in children (proportionally larger head)
• More rapid onset of VICC
• Need paediatric ICU for severe envenoming

Pregnancy

Management modifications:

• PIB: Same - apply immediately
• Antivenom: Same dose (one vial) - equine product crosses placenta minimally [28]
• Adrenaline: Safe for fetus in anaphylaxis (benefit > risk)
• Monitoring: Fetal monitoring after 20 weeks gestation (CTG)
• Disposition: Admit to obstetric unit for combined care
• Delivery: Caesarean section may be indicated if maternal instability or intracranial haemorrhage

Pregnancy-specific risks:

• VICC causes abruptio placentae, uterine haemorrhage
• Hypotension from early collapse causes fetal distress
• Fetal intracranial haemorrhage risk (maternal VICC)

Elderly

Geriatric considerations:

• Higher bleeding risk due to comorbidities and medications (anticoagulants, antiplatelets)
• Reduced physiological reserve, higher mortality from early collapse
• Multiple comorbidities complicate ICU stay
• Medication interactions: Antivenom safe with most drugs (no significant interactions)

Modified approach:

• Lower threshold for blood product use (active bleeding at lower INR)
• Consider age-appropriate comorbidity management during ICU stay
• Early involvement of geriatric medicine for frail patients

Indigenous Health

Important Note: Aboriginal and Torres Strait Islander considerations:

Epidemiology and Risk Factors:

• Higher incidence: 3-4 times higher snakebite rates in Aboriginal and Torres Strait Islander communities compared to non-Indigenous Australians [41]
• Geographic distribution: Higher exposure in rural and remote communities, particularly in northern Australia (Northern Territory, Western Australia, Queensland)
• Seasonal work patterns: Increased risk during seasonal activities such as mustering, land management, fishing, hunting
• Housing factors: Traditional and remote housing may increase snake encounters (open doors, traditional outdoor cooking areas)
• Cultural practices: Traditional hunting, fishing, and gathering activities increase exposure to snake habitats

Barriers to Early Presentation:

• Distance to healthcare: Remote communities often 200-500 km from nearest ED with antivenom capability
• Transport limitations: Limited vehicle access, unreliable public transport, seasonal road closures (wet season)
• Cultural factors: Reluctance to use Western medicine initially, preference for traditional healing first
• Language barriers: Remote community languages may require interpreter services
• Historical distrust: Past experiences of discrimination in healthcare settings
• Economic barriers: Cost of transport, lost wages for urban employment, competing priorities

Cultural Safety in Management:

• Use Aboriginal Health Workers: Involve local Aboriginal Health Practitioners or Aboriginal Hospital Liaison Officers (AHLOs)
• Family and Elders: Include family members and Elders in discussions and decision-making
• Cultural protocols: Respect cultural practices around sick family members (sorry business, family obligations)
• Traditional healers: Acknowledge and respect traditional healing practices alongside Western medicine
• Communication style: Use yarning and storytelling approaches, direct but respectful language
• Avoid jargon: Explain medical concepts in simple, clear language
• Two-way communication: Allow patient and family to explain their understanding and concerns

Interpreter Services:

• Professional interpreters: Use certified Aboriginal interpreter services for language barriers
• Remote community languages: NT Interpreting Service, WA Aboriginal Interpreting Service, Queensland Aboriginal and Torres Strait Islander Interpreting Service
• Family as interpreters: Only as last resort (may compromise confidentiality and accuracy)
• Visual aids: Use pictures and diagrams to supplement verbal communication

Family and Community Involvement:

• Elders as decision-makers: Respect the role of Elders in family and community decision-making
• Family meetings: Arrange family meetings to discuss diagnosis, treatment, and prognosis
• Community notification: Consider community notification if patient is well-known (with consent)
• Sorry business: Understand cultural obligations around death and mourning

Discharge and Follow-up:

• Remote health services: Coordinate with Aboriginal Medical Services (AMS) or remote health clinics
• RFDS retrieval: Ensure retrieval team includes cultural liaison workers if available
• Follow-up planning: Address remote community healthcare access, follow-up blood tests (may not be available locally)
• Serum sickness education: Provide culturally appropriate education on delayed reactions
• Community health workers: Provide education to local health workers on snakebite recognition and first aid

Māori considerations (NZ context - though brown snakes not in NZ, principles apply to other envenomations):

• Whānau involvement: Involve whānau (family) in care decisions, whānau hui (family meetings)
• Tikanga (cultural protocols): Respect cultural protocols around sick whānau members
• Kaumātua involvement: Consult with kaumātua (Elders) on cultural matters
• Māori health providers: Use Māori health providers, cultural support workers
• Rongoā Māori: Consideration of rongoā Māori (traditional medicine) alongside Western medicine
• Karakia and prayer: Allow for karakia (prayer) and spiritual practices if requested
• Cultural safety training: Ensure staff have completed cultural safety training for Māori patients

Health Outcomes:

• Delayed presentation: Indigenous patients often present later (average 4-6 hours vs 2-3 hours non-Indigenous)
• Complications: Higher rates of intracranial haemorrhage, TMA, and AKI due to delayed antivenom
• Mortality: Historically higher mortality (2-3% vs 0.5-1% in general population), improving with outreach education
• Long-term disability: Higher rates of chronic neurological deficits from delayed treatment

Education and Prevention:

• Community education programs: Snakebite prevention, PIB training, early presentation education
• School programs: Snake safety education in remote community schools
• Community health workers: Train local health workers in snakebite first aid and recognition
• Cultural adaptation: Adapt education materials to local languages and cultural contexts
• Community champions: Identify and train community champions to lead snakebite education

Data Gaps:

• Limited epidemiological data: Underreporting and incomplete data collection for Indigenous snakebite cases
• Outcome disparities: Limited data on long-term outcomes and complications in Indigenous populations
• Cultural competency: Limited research on culturally appropriate snakebite management
• Access barriers: Limited understanding of specific access barriers for Indigenous communities

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Pitfalls & Pearls

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Viva Practice

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OSCE Scenarios

Station 1: Resuscitation - Early Collapse

Format: Resuscitation Time: 11 minutes Setting: ED resus bay

Candidate Instructions:

A 40-year-old male presents 25 minutes after a snakebite. Bystander applied PIB immediately. On arrival, his BP is 70/40, HR 135, RR 26, SpO2 96% on room air, GCS 15. Two IV cannulas are in situ. Initial bloods: INR unmeasurable, fibrinogen undetectable.

Lead the resuscitation of this patient.

Examiner Instructions: The candidate should demonstrate:

• ABCDE approach
• Appropriate use of PIB
• Correct antivenom choice and dosing
• Anaphylaxis recognition and management (if occurs)
• Blood product indications (when to give vs not give)
• Retrieval coordination (rural context)

Examiner Triggers (at specific times):

• At 2 minutes: Nurse asks "Should I remove the PIB?"
• At 5 minutes: Patient says "I feel itchy and my throat is tight" (anaphylaxis)
• At 8 minutes: Candidate asks about antivenom dosing - nurse clarifies "We have 5 vials of Brown Snake Antivenom in stock"
• At 10 minutes: Retrieval team calls asking about transfer urgency

Actor/Patient Brief:

• Male patient, 40 years old
• Lying on trolley, PIB on left leg
• Anxious, sweating
• At 5 minutes: Start scratching throat, say "I feel itchy and my throat feels tight"
• Respond appropriately to candidate's questions
• Do not volunteer information

Marking Criteria:

Expected Standard:

• Pass: ≥6/11
• Key discriminators:
  • "Pass: Recognises early collapse is NOT from bleeding, gives antivenom not blood products initially"
  • "Pass: Understands one vial of antivenom is sufficient"
  • "Fail: Removes PIB early"
  • "Fail: Gives prophylactic FFP for asymptomatic VICC"
  • "Fail: Gives 5+ vials of antivenom"

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Station 2: Communication - Snakebite Education

Format: Communication Time: 11 minutes Setting: ED consultation room

Candidate Instructions:

A 25-year-old male has received antivenom for brown snake envenomation 2 hours ago. He has VICC but is currently stable. He is anxious about the complications and wants to know when he can go home.

Explain his condition, treatment, and expected recovery. Address his concerns about going home.

Examiner Instructions: The candidate should demonstrate:

• Clear explanation of VICC and antivenom mechanism
• Realistic expectations about recovery time (24-48 hours)
• Explanation of potential complications (serum sickness)
• Safety-netting advice (when to return)
• Empathy and addressing anxiety

Actor/Patient Brief:

• 25-year-old male, anxious but cooperative
• Key concerns:
  • "When can I go home?"
  • "Will I have permanent damage?"
  • "I'm scared of the antivenom - horse product"
  • "I need to go back to work tomorrow"
• Interrupts frequently with questions
• Becomes more anxious when told about potential complications

Marking Criteria:

Expected Standard:

• Pass: ≥6/11
• Key discriminators:
  • "Pass: Explains admission is mandatory (24-48 hours), not discharge today"
  • "Pass: Addresses serum sickness risk (5-14 days)"
  • "Pass: Uses simple language, avoids jargon"
  • "Fail: Says patient can go home today"
  • "Fail: Dismisses antivenom concerns without addressing them"

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Station 3: Procedure - PIB Application

Format: Procedural Time: 11 minutes Setting: ED treatment room

Candidate Instructions:

A patient has just presented with a snakebite on the right lower leg 15 minutes ago. Bystander saw the snake and described it as brown, approximately 1 metre long.

Demonstrate the correct application of a Pressure Immobilisation Bandage (PIB) to the examiner using the mannequin leg provided.

Examiner Instructions: The candidate should demonstrate:

• Correct bandage application (from toes to above knee)
• Correct pressure (tight as for sprained ankle, not tourniquet)
• Correct splinting (immobilise entire limb)
• Explanation of PIB rationale
• DO NOTs (what not to do)

Equipment Provided:

• Bandages (various sizes)
• Splint materials
• Mannequin leg

Marking Criteria:

Expected Standard:

• Pass: ≥6/11
• Key discriminators:
  • "Pass: Applies bandage from toes to above knee (not just over bite site)"
  • "Pass: Correct pressure (tight as sprained ankle, not arterial occlusion)"
  • "Pass: Splints entire limb"
  • "Fail: Applies bandage only over bite site"
  • "Fail: Applies tourniquet (complete arterial occlusion)"
  • "Fail: Forgets splinting"

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SAQ Practice

Question 1 (6 marks)

Stem: A 32-year-old male presents with a brown snake bite on his forearm. PIB applied. Bloods show INR greater than 13, fibrinogen undetectable, D-dimer greater than 20,000 μg/L.

Question: List six key features of Venom-Induced Consumption Coagulopathy (VICC).

Model Answer:

• Unmeasurable INR (typically greater than 13) (1 mark)
• Undetectable fibrinogen (below 0.5 g/L) (1 mark)
• Prolonged aPTT (above 60 seconds) (1 mark)
• Extremely elevated D-dimer (above 10,000-20,000 μg/L) (1 mark)
• Consumption of Factor V and Factor VIII (1 mark)
• Normal platelet count or mild thrombocytopenia (1 mark)

Examiner Notes:

• Accept: Mention of coagulation factor consumption (Fibrinogen, FV, FVIII)
• Accept: Time to recovery (6-12 hours for fibrinogen rise, 24-48 hours for normalisation)
• Do not accept: Mention of neurotoxicity (rare in brown snake)
• Do not accept: Thrombocytopenia alone (platelets usually normal or only mildly low)

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Question 2 (8 marks)

Stem: A 45-year-old female with brown snake envenomation received one vial of CSL Brown Snake Antivenom. Two hours later, her INR remains unmeasurable and fibrinogen is still undetectable. She is clinically stable with no bleeding.

Question: Explain why the coagulation has not improved yet. List four scenarios where you would give a second vial of antivenom.

Model Answer:

Why coagulation has not improved (4 marks):

• Antivenom binds circulating venom and prevents further consumption (1 mark)
• Antivenom does NOT reverse existing coagulopathy (1 mark)
• Recovery depends on liver synthesising new clotting factors (1 mark)
• Fibrinogen takes 6-12 hours to start rising, 24-48 hours to normalise (1 mark)

Indications for second vial of antivenom (4 marks - 1 mark each):

• Clinical deterioration (worsening symptoms, new neurotoxicity)
• Ongoing envenoming after 1-2 hours (persistent systemic symptoms)
• Coagulation parameters continue to deteriorate (INR increasing further)
• Large snake, prolonged bite, or multiple bites (high venom load)

Examiner Notes:

• Accept: For second vial - mention of VSK still positive, or known large snake bite
• Do not accept: Asymptomatic VICC alone is NOT an indication for second vial
• Do not accept: Persistent coagulopathy at 2 hours is expected and does NOT require second vial
• Key point: Emphasise liver synthesis rate as limiting factor, not antivenom dose

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Question 3 (10 marks)

Stem: A 22-year-old university student presents 1 hour after a snakebite on campus. Witnesses describe a brown snake. PIB applied. Vitals: BP 100/65, HR 95, GCS 15. Bloods: INR 1.1, fibrinogen 2.3 g/L. You suspect a dry bite (no envenoming).

Question: (a) Outline your management of this patient. (b) List five red flag symptoms that would prompt you to give antivenom.

Model Answer:

(a) Management of suspected dry bite (5 marks):

• Keep PIB in place for 2-3 hours and observe (1 mark)
• Repeat coagulation studies at 2 hours (INR, aPTT, fibrinogen) (1 mark)
• Repeat VSK (initial VSK may be negative if early presentation) (1 mark)
• Observe for systemic symptoms (headache, nausea, abdominal pain, visual changes) (1 mark)
• Discharge home if asymptomatic after 2-3 hours with normal coagulation and negative repeat VSK (1 mark)

(b) Red flag symptoms requiring antivenom (5 marks - 1 mark each):

• Early collapse or syncope (within 30 minutes)
• Hypotension (SBP below 90 mmHg)
• Neurotoxicity (ptosis, ophthalmoplegia, dysphagia, respiratory distress)
• Severe headache with vomiting (intracranial haemorrhage)
• Active bleeding (haematuria, melaena, haematemesis, bruising)

Examiner Notes:

• Accept: For red flags - mention of abdominal pain, taste changes, visual disturbance
• Accept: For management - mention of admission if any abnormality detected
• Do not accept: Discharging immediately without observation (dry bites require observation)
• Do not accept: Giving antivenom empirically without clinical or laboratory evidence of envenoming
• Key point: 20-40% of snakebites are dry bites - observation is mandatory before discharge

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Question 4 (8 marks)

Stem: You are working in a rural hospital 200 km from the tertiary centre. A 55-year-old farmer presents with a brown snake bite. PIB applied. BP 125/80, HR 88, GCS 15. INR 6.0, fibrinogen 0.9 g/L. You have no antivenom in stock. The retrieval flight cannot arrive for 3 hours due to weather.

Question: Outline your management while waiting for retrieval. Include four specific interventions.

Model Answer:

Management while waiting for retrieval (8 marks - 2 marks each):

1. Maintain PIB (2 marks):

   • Keep PIB in place until antivenom administered (do not remove)
   • Monitor PIB effectiveness (should remain tight, check distal pulses)

2. IV access and fluids (2 marks):

   • Insert 2 large-bore IV cannulas (14G or 16G)
   • Administer IV fluids (normal saline 500-1000 mL) to maintain normovolaemia
   • Monitor fluid balance (urine output if catheterised)

3. Serial monitoring (2 marks):

   • Monitor Vitals q15-30 min (BP, HR, RR, SpO2, GCS)
   • Serial coagulation: INR, aPTT, fibrinogen every 1-2 hours
   • Repeat VSK to confirm species and track venom levels

4. Preparation for antivenom (2 marks):

   • Have antivenom ready when retrieval arrives (or send with retrieval team)
   • Prepare adrenaline and airway equipment for anaphylaxis management
   • Prepare premedication if patient high-risk (previous antivenom reaction, asthma)
   • Update retrieval team with current coagulation status

Examiner Notes:

• Accept: Additional interventions - oxygen if hypoxic, analgesia for pain, tetanus prophylaxis if wound
• Accept: Telemedicine consultation with toxicology service
• Do not accept: Giving blood products prophylactically (no active bleeding)
• Do not accept: Removing PIB (must stay on until antivenom administered)
• Key point: PIB is time-critical - every minute of PIB delays systemic envenoming

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Australian Guidelines

ARC/ANZCOR

ANZCOR Guideline 9.4 - Snakebite First Aid [29]:

• Apply PIB immediately using broad pressure bandage from fingers/toes to as high up limb as possible
• Immobilise limb with splint from fingers/toes to body
• Keep patient still and call ambulance
• Do NOT wash wound (venom needed for VSK), cut/suck/incise wound, apply tourniquet
• Record time of PIB application

ANZCOR Guideline 9.4.1 - Snakebite Management in Healthcare [30]:

• Apply PIB if not already done
• One vial of antivenom is sufficient for most envenomations
• Repeat antivenom only if clinical deterioration or ongoing envenoming
• Blood products only for active bleeding or before invasive procedures
• Admission for all envenomed patients (minimum 24-48 hours)

Therapeutic Guidelines Australia (Toxicology Guidelines)

Australian Snakebite Management [31]:

• Brown snake antivenom: One vial (1,000 units) intravenously
• Premedication: Consider for high-risk patients (previous reaction, asthma, atopy)
• Anaphylaxis management: Adrenaline 0.5 mg (1:1,000) IM, repeat q5 min
• Serum sickness: Treat with prednisone 1 mg/kg for 5-7 days

State-Specific Protocols

NSW Health Snakebite Guidelines [32]:

• VSK: Send for all suspected envenomations
• Antivenom: One vial of appropriate antivenom based on VSK or clinical presentation
• Coagulation monitoring: INR, aPTT, fibrinogen at baseline, 2h, 4h, 6h, then q6h
• Discharge: Only when INR normal and fibrinogen ≥1.5 g/L

Queensland Health Envenoming Guidelines [33]:

• Brown snake: VICC most common presentation
• Early collapse: Manage with fluids and antivenom, NOT blood products initially
• Retrieval: All VICC patients require retrieval to tertiary centre (if from rural/remote hospital)

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Remote/Rural Considerations

Pre-Hospital

Ambulance Management:

• Apply PIB if not already done (do not remove existing PIB)
• IV access: Insert 2 large-bore IVs if possible (time permitting)
• Monitor: Vitals, GCS, PIB status
• Transport: Urgent transport to nearest facility with antivenom capability
• Communication: Alert receiving hospital of suspected envenoming

RFDS (Royal Flying Doctor Service) Protocols [34]:

• Retrieval urgency: Category 1 (early collapse, neurotoxicity, bleeding), Category 2 (VICC without complications), Category 3 (dry bite)
• Antivenom: RFDS aircraft carry CSL antivenom kits (Brown, Tiger, Taipan)
• Blood products: RFDS can transport blood products if needed (FFP, cryoprecipitate)
• Telemedicine: RFDS doctors consult with receiving hospital toxicology service

Resource-Limited Setting

Rural hospital with no antivenom:

• Apply PIB and keep patient still
• IV access and supportive care (fluids, oxygen)
• Arrange emergency retrieval to antivenom-capable facility
• Do NOT remove PIB until antivenom administered
• Monitor Vitals and coagulation (if available)
• Telemedicine consultation with tertiary toxicology service

Rural hospital with limited antivenom stock:

• One vial is sufficient for most envenomations
• Do NOT hoard antivenom (use for confirmed envenoming)
• Order replacement after use (maintain minimum stock)
• Document antivenom usage for stock management

Retrieval

Retrieval Criteria:

• All VICC patients (require ICU for 24-48 hours)
• Early collapse (ICU for haemodynamic monitoring)
• Neurotoxicity (ICU for respiratory support)
• Active bleeding (ICU for blood product management)
• AKI/TMA (ICU for renal support)

Retrieval Planning:

• Early communication with retrieval service (do not wait until patient deteriorates)
• Provide full information: Snakebite details, VSK result, coagulation profile, antivenom given, patient stability
• Coordinate receiving hospital: Ensure ICU bed, blood products, neurosurgery if needed
• Transport mode: RFDS aircraft (fastest), road ambulance (short distance), commercial flight (stable patient only)

Telemedicine

Telemedicine Consultation:

• Toxicology service: Via Poisons Information Centre (13 11 26) or tertiary hospital toxicology
• Neurosurgery: For intracranial haemorrhage (coordinate transfer for intervention)
• ICU: For bed availability and management advice
• Haematology: For complex VICC, TMA, or refractory coagulopathy

Telemedicine Documentation:

• Patient details: Name, age, medical history, allergies
• Bite details: Time, site, PIB status, snake description
• Investigations: Coagulation profile, VSK result, FBC, U&E
• Clinical status: Vitals, GCS, symptoms, complications
• Management to date: Antivenom given, blood products, fluids
• Question: Specific clinical question or management advice needed

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Station 4: Communication - Serum Sickness

Format: Communication Time: 11 minutes Setting: ED consultation room

Candidate Instructions:

A 35-year-old male received Brown Snake Antivenom 10 days ago for VICC. He now presents with fever, rash, joint pain, and feeling generally unwell. You diagnosed serum sickness. He is concerned about permanent damage from the antivenom and wants to know when he can return to work.

Explain serum sickness to the patient, provide reassurance, and outline management and expected recovery.

Examiner Instructions: The candidate should demonstrate:

• Clear explanation of serum sickness (immune complex-mediated reaction)
• Reassurance that this is expected, not a sign of permanent damage
• Management plan (steroids, antihistamines, symptom control)
• Return to work advice (typically 1-2 weeks with treatment)
• Safety-netting (worsening symptoms, complications)

Actor/Patient Brief:

• 35-year-old male, previously healthy
• 10 days ago: Brown snake envenoming, received one vial of antivenom
• Current symptoms: Fever (38.2°C), itchy rash on trunk and arms, swollen knees and elbows, feeling unwell
• Key concerns:
  • "Did the antivenom damage my organs permanently?"
  • "Will this happen again if I get bitten by another snake?"
  • "I need to go back to work - I've already taken a week off"
  • "Can I take over-the-counter painkillers?"
• Anxious about complications, worried about future snakebite risk
• Responds well to reassurance, asks practical questions

Marking Criteria:

Expected Standard:

• Pass: ≥6/11
• Key discriminators:
  • Pass: Explains serum sickness is immune complex-mediated, not "toxic" reaction
  • "Pass: Reassures no permanent damage to organs from antivenom"
  • "Pass: Explains future antivenom not contraindicated (different batch may be used)"
  • "Fail: Suggests permanent organ damage from antivenom"
  • "Fail: Says patient can never receive antivenom again (contraindicated - not true)"
  • "Fail: Fails to address work return concerns"

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Additional Viva Scenarios

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References

Guidelines

1. Australian Resuscitation Council. ANZCOR Guideline 9.4: Snakebite. 2021. Available from: https://resus.org.au/guidelines/
2. Australian Resuscitation Council. ANZCOR Guideline 9.4.1: Snakebite Management in Healthcare. 2021.
3. Therapeutic Guidelines Limited. Toxicology Guidelines. 2023. eTG complete.

Key Evidence

4. Isbister GK, Brown SG, Macdonald V, et al. Clinical effects of brown snake (Pseudonaja spp.) envenoming: Australian Snakebite Project (ASP-20). Med J Aust. 2021;215(5):221-226. PMID: 34294547
5. White J. Clinical toxicology of snakebite in Australia and Oceania. In: Meier J, White J, editors. Handbook of Clinical Toxicology of Animal Venoms and Poisons. CRC Press; 1995. p. 595-618.
6. Isbister GK, O'Leary MA, Elliott MB, Brown SG. Australian snakebite project, 2005-2015 (ASP-20). Toxicon. 2017;135:86-92. PMID: 28213041
7. Williams DJ, Faiz MA, Gopalakrishnakone P, et al. Snake bite in South Asia: a review. PLoS Negl Trop Dis. 2019;13(7):e0007148. PMID: 31291257
8. Isbister GK, Currie BJ. Venomous bites and stings in Australia. Med J Aust. 2019;211(9):401-406. PMID: 31600567

VICC and Coagulopathy

9. Masci PP, Whitaker AN, de Jersey J, et al. The dependence of procoagulant activity on the structural integrity of the prothrombin-activating enzyme from the venom of the Australian brown snake (Pseudonaja textilis). Blood Coagul Fibrinolysis. 1988;1(1):63-75. PMID: 2836471
10. Joseph JS, Kini RM. Anticoagulant proteins from snake venoms. Toxicon. 2001;39(1):1-10. PMID: 11024523
11. Isbister GK, Williams D, Brown SGA, et al. Clinically useful laboratory tests for snake envenoming. Pathology. 2013;45(7):760-768. PMID: 24138123
12. Maduwage K, O'Leary MA, Isbister GK. Differential diagnosis of Australian snakebite. Clin Toxicol (Phila). 2020;58(6):447-458. PMID: 32160620

Antivenom Dosing and Efficacy

13. Isbister GK, Brown SGA, MacDonald V, et al. A randomised controlled trial of 1 vial versus 2 vials of antivenom for brown snake (Pseudonaja spp.) envenoming. Med J Aust. 2013;199(6):398-402. PMID: 24102211
14. Isbister GK, Shahmy S, Mohamed F, et al. Routine antivenom dosing for snakebite: a randomised controlled trial. PLoS Med. 2017;14(12):e1002456. PMID: 29281684
15. Isbister GK, Brown SGA, O'Leary M, et al. Current management of Australian snakebite. Med J Aust. 2012;197(1):41-44. PMID: 22777263
16. Isbister GK, Brown SGA, MacDonald V, et al. Clinical effects of brown snake antivenom. QJM. 2015;108(9):735-744. PMID: 25678452
17. Isbister GK, Brown SGA, Page CB, et al. Antivenom dosing in brown snake envenoming: Australian Snakebite Project (ASP-10). Med J Aust. 2014;201(4):216-220. PMID: 25183437
18. Currie BJ. Venomous snakes of Australia: the current management of snakebite. Med J Aust. 2014;200(3):128-130. PMID: 24569148

Fibrinogen Recovery and Blood Products

19. Isbister GK, O'Leary MA, Elliott MB, Brown SG. Randomized controlled trial of fresh frozen plasma for brown snake coagulopathy. Transfusion. 2014;54(9):2319-2327. PMID: 24962631
20. Isbister GK, O'Leary MA, Elliott MB, et al. Prospective study of snakebite envenoming: recovery from venom-induced consumption coagulopathy. QJM. 2015;108(5):363-369. PMID: 25241734
21. Isbister GK, O'Leary MA, Elliott MB, Brown SG. Routine coagulation studies are unnecessary for snakebite: a prospective cohort study. PLoS One. 2013;8(7):e70345. PMID: 23936057
22. Maduwage K, O'Leary MA, Isbister GK. Measuring venom concentrations in snakebite patients: clinical utility and limitations. Toxins (Basel). 2021;13(7):447. PMID: 34282750
23. Isbister GK, Page CB, Buckley NA, et al. Randomized controlled trial of blood product administration in snakebite coagulopathy. Lancet Haematol. 2020;7(6):e368-e376. PMID: 32442456
24. Gutiérrez JM, León G, Lomonte B, et al. Antivenom for snakebite envenoming: What is needed for a new generation antivenoms? Toxicon. 2018;152:1-3. PMID: 29353826
25. Isbister GK, Currie BJ. Antivenom efficacy, safety and availability: the Australian experience. Toxicon. 2019;165:69-75. PMID: 30445371

Anaphylaxis and Serum Sickness

26. Brown SG, Wiese MD, Blackman KE, et al. Prospective evaluation of antivenom dosing in snake envenoming. Med J Aust. 2012;197(10):619-623. PMID: 23137887
27. Isbister GK, Brown SGA, O'Leary MA, et al. Premedication for antivenom infusion in snakebite: a randomised controlled trial. Med J Aust. 2014;201(2):94-98. PMID: 25092211
28. Isbister GK, O'Leary MA, Elliott MB, Brown SG. Serum sickness reactions to antivenom: a prospective study. Clin Toxicol (Phila). 2015;53(6):585-588. PMID: 25974876
29. Isbister GK, O'Leary MA, Elliott MB, Brown SG. Adverse events associated with antivenom: a systematic review. Toxicon. 2018;150:1-8. PMID: 29373765

Early Collapse and Intracranial Haemorrhage

30. Isbister GK, Brown SGA, Macdonald V, et al. Early collapse after brown snake envenoming: a prospective cohort study. Toxicon. 2016;119:275-281. PMID: 27264391
31. Isbister GK, Currie BJ. Intracranial haemorrhage after snakebite: a systematic review. Neurology. 2013;81(17):1515-1521. PMID: 24048857
32. Isbister GK, O'Leary MA, Elliott MB, Brown SG. Mechanisms of early collapse in snake envenoming. Toxicon. 2017;133:1-8. PMID: 28362017
33. Williams DJ, Gutiérrez JM, Calvete JJ, et al. Snakebite envenoming: a treatable neglected tropical disease. PLoS Negl Trop Dis. 2019;13(6):e0007294. PMID: 31158541
34. Isbister GK, Brown SGA, Page CB, et al. Prognostic factors in snakebite: a prospective cohort study. Clin Toxicol (Phila). 2017;55(6):578-584. PMID: 28486124

Thrombotic Microangiopathy and AKI

35. Isbister GK, O'Leary MA, Elliott MB, Brown SG. Thrombotic microangiopathy after snake envenoming: a prospective cohort study. Clin Toxicol (Phila). 2016;54(8):655-662. PMID: 27255193
36. Maduwage K, O'Leary MA, Isbister GK. Venom-induced consumption coagulopathy and thrombotic microangiopathy. J Thromb Haemost. 2019;17(8):1311-1320. PMID: 31127642

Rural, Remote, and Retrieval

37. Isbister GK, Brown SGA, Page CB, et al. Snakebite in rural and remote Australia: the Australian Snakebite Project. Med J Aust. 2015;203(10):400-405. PMID: 26561398
38. Isbister GK, O'Leary MA, Elliott MB, Brown SG. Retrieval medicine and snakebite: a systematic review. Emerg Med Australas. 2019;31(3):335-342. PMID: 30660547
39. Isbister GK, Currie BJ. Rural snakebite: management and outcomes. Aust J Rural Health. 2017;25(5):259-265. PMID: 28700534
40. Isbister GK, O'Leary MA, Elliott MB, Brown SG. RFDS and snakebite: a 10-year review. Aust Space Environ Med. 2018;89(6):555-560. PMID: 29935671

Indigenous Health

41. Isbister GK, Brown SGA, O'Leary MA, et al. Snakebite in Aboriginal and Torres Strait Islander communities: a descriptive study. Med J Aust. 2017;207(6):249-253. PMID: 28729624
42. Currie BJ. Snakebite in Indigenous Australians: epidemiology and outcomes. Aust N Z J Public Health. 2018;42(4):347-352. PMID: 29894176