Clinical Practice Guidelines

Snakebite

  • This guideline has been adapted for statewide use with the support of the Victorian Paediatric Clinical Network
    It should not be used outside Victoria due to regional differences in Snake species 

    See also

    This guideline is based on the Emergency Care Improvement & Innovation Clinical Network snakebite guideline
    www.health.vic.gov.au/

    Specific advice about children with potential snakebite should be sought from a clinical toxicologist (Poisons Information Centre 131126, 24 hrs/day)

    Background

    Snake bite is uncommon in Victoria and envenomation (systemic poisoning from the bite) is rare. The bite site may be evidenced by fang marks, one or multiple scratches. The bite site may be painful but usually is not.

    Major venomous snakes in Victoria and effects of envenomation:

    Snake

    Coagulopathy

    Neurotoxicity

    Myotoxicity

    Systemic symptoms

    Cardiovascular effects

    TMA

    Brown

    VICC

    Rare and mild

    -

    <50%

    Collapse (33%)
    Cardiac arrest (5%)

    10%

    Tiger

    VICC

    Uncommon

    Uncommon

    Common

    Rare

    5%

    Red-bellied black

    Anticoagulant

    -

    Uncommon

    Common

    -

    -

    VICC = Venom-induced consumptive coagulopathy (abnormal INR, fibrinogen very low, d-dimer high)
    Anticoagulant = APTT 1.5–2.5 x normal ± minor elevation INR. D-dimer and fibrinogen usually normal
    TMA = thrombotic microangiography. Fragmented red blood cells on blood film, thrombocytopenia and a rising creatinine.
    Systemic Symptoms = see below

    Tiger snake bites may develop local swelling. Brown snake bites may result in sudden collapse and death, the mechanism of which is unclear.
    Snake collectors (or their children) may be bitten by exotic or non-Victorian snakes. There are no sea snakes in Victoria, however land-based snakes can swim. 

    Assessment

    Focused on evidence of envenomation 

    Once the possibility of snakebite has been raised, it is important to determine whether a child has been envenomed to establish the need for anitvenom. This is usually done taking into consideration the combination of circumstances, symptoms, examination and laboratory test results. Most people bitten by snakes in Australia do not become significantly envenomed.

    History and Examination:

    Circumstances

    Symptoms

    Examination

    • Confirmed or witnessed bite versus suspicion that bite might have occurred
    • Were there multiple bites?
    • When?
    • Where?
    • First aid?
    • Past history?
    • Medications?
    • Allergies?
    • Headache
    • Nausea or vomiting
    • Abdominal pain
    • Blurred or double vision
    • Slurring of speech
    • Muscle weakness
    • Respiratory distress
    • Bleeding from the bite site or elsewhere
    • Passing dark or red urine
    • Local pain or swelling at bite
    • Pain in lymph nodes draining the bite area
    • Loss of consciousness and/or convulsions
    • Evidence of a bite / multiple bites.  Swab for venom but do not test.
    • Evidence of venom movement (e.g. swollen or tender draining lymph nodes)
    • Neurotoxic paralysis (ptosis, ophthalmoplegia, diplopia, dysarthria, limb weakness, respiratory distress)
    • Coagulopathy (bleeding gums, prolonged bleeding from venepuncture sites or other wounds, including the bite site)
    • Muscle damage (muscle tenderness, pain on movement, weakness, dark or red urine indicating myoglobinuria)

    Investigations:

    For timing and interpretation of blood tests see management flow chart below.

    • Initial blood tests: coagulation screen (INR, APTT, fibrinogen), FBE and film, CK, EUC, LDH, LFT.
    • Serial blood tests: INR, APTT, fibrinogen, CK, FBE, EUC. 

    Role of snake venom detection kit (VDK) 

    • The choice of antivenom is based on the clinical syndrome and local geographical patterns of snake distribution. 
    • Attempted identification of snakes by witnesses should never be relied upon as snakes of different species may have the same colouring or banding.
    • Snake venom detection kits can be useful but in inexperienced hands they can have significant rates of snake misidentification, false positives and false negatives. The results should not over-ride clinical and geographical data. Discuss use and results with a clinical toxicologist (e.g. Poisons Centre 13 11 26).
    • If used, a VDK should be used on a bite site swab, and a single operator should be dedicated to perform the VDK interpretation and should do so free from other clinical responsibility and interruption. This takes 20-30 minutes, and as such should be omitted in the unwell or arrested patient. A brief lapse in concentration when watching for colour change in the VDK can result in a false reading.
    • If there is no apparent bite, a VDK may be done on urine, but never blood.
    • Most venomous snakebites in Victoria are from brown or tiger snakes, and both may present with an initial coagulopathy on blood testing. As a result, it may be appropriate to administer one vial each of brown and tiger snake antivenom where envenomation is evident and a person experienced in the use and interpretation of a venom detection kit is not immediately available. 

    It is recommended that all cases of envenoming are discussed with a clinical toxicologist to guide treatment (including choice of antivenom) and follow-up healthcare after discharge (e.g. Poisons Centre 13 11 26). 

    Assessment of Severity (Indications for Administration of Antivenom):

    The presence of any of the following indicates that envenomation has occurred and treatment with antivenom is indicated:

    • Any evidence of neurotoxic paralysis (e.g. ptosis, ophthalmoplegia, limb weakness, respiratory effects)
    • Significant coagulopathy (e.g. unclottable blood, INR>1.3 or prolonged bleeding from wounds and venepunctures)
    • History of unconsciousness, collapse, convulsions or cardiac arrest

    There are a number of relative indications for antivenom that require expert interpretation. 

    • Significant systemic symptoms (eg – headache, abdominal pain, vomiting)
    • Any abnormality of INR, APTT, fibrinogen, d-dimer, full blood count (leucocytosis, evidence of TMA) or CK >1000

    These should be discussed with a clinical toxicologist (Poisons Information Centre 131126) to determine if antivenom is required. 

    Management

    First Aid

    • Apply a pressure immobilisation bandage - immobilise joints either side of bite (use a splint), lay the patient down. The aim is to prevent lymphatic spread of venom, not to stop blood supply – make the bandage about as firm as you would use on a sprained ankle. See www.avru.org

    DO NOT remove bandage until in a centre with full treatment facilities, including available anti-venom and access to laboratory testing. Do not wash or clean the bite site in any way.

    snakebite

    Giving Antivenom

    • Giving antivenom should occur in consultation with a clinical toxicologist. In unwell patients in whom a consultation will be delayed give one vial of tiger and one vial of brown.
    • Dilute one vial in 100mls 0.9% saline and give IV over 15-30 min.
    • There is no weight based calculation for antivenom (the snake delivers the same amount of venom regardless of the size of the patient.) One vial of antivenom is enough to neutralize the venom that can be delivered by one snake. Clinical recovery takes time after antivenom administration, multiple vials do not speed recovery.
    • There is a risk of anaphylaxis with antivenom administration – be prepared to treat (with fluids, adrenaline etc. see Anaphylaxis guideline). If anaphylaxis occurs consult with a clinical toxicologist. 

    Venom induced coagulopathy takes time to reverse. More antivenom than recommended will not aid recovery of clotting factors. The role of FFP is limited. Coagulopathy correction may be indicated if the patient is bleeding and should always be discussed with a clinical toxicologist.

    Discharge Criteria & Follow up

    Children with suspected snakebite should only be discharged in daylight hours (neurological signs can be subtle and only evident when children are awake) 

    When to admit/consult local paediatric team 

    Serial blood tests and clinical examinations take a minimum of 12 hours after the time of the bite; these can occur in Emergency Departments or with inpatient units depending on local experience and level of comfort 

    When to consider transfer to tertiary centre

    Envenomed children should be discussed with a clinical toxicologist and considered for transfer to a tertiary centre depending on clinical signs 

    For advice and inter-hospital (including ICU level) transfers ring the PIPER 1300 137 650

    Parent information sheet:

    www.health.vic.gov.au 

    Information Specific to RCH

    Children undergoing serial testing are suitable for both the ED Observation ward and the Short Stay Unit.
    Envenomed children should be considered for PICU admission but may be suitable for a ward General Medical admission depending on clinical signs and degree of coagulopathy.
     

    Information Specific to Monash Health

    The Monash Health clinical toxicologist on-call should be consulted in all cases of suspected snakebite.
    Patients undergoing serial bloods tests are suitable for either ED Short Stay or ward admission, depending on site.
    Patients who have received anti-venom may be suitable for a toxicology, inpatient or PICU (Clayton) admission depending on age and clinical features.