Snake bite

Disclaimer These guidelines have been produced to guide clinical decision making for the medical, nursing and allied health staff of Perth Children’s Hospital. They are not strict protocols, and they do not replace the judgement of a senior clinician. Clinical common-sense should be applied at all times. These clinical guidelines should never be relied on as a substitute for proper assessment with respect to the particular circumstances of each case and the needs of each patient. Clinicians should also consider the local skill level available and their local area policies before following any guideline.  Read the full CAHS clinical disclaimer

Aim

To guide staff with the assessment and management of snake bite.

This is a general approach to snake bite – for specific management details, please contact Poisons Information on 13 11 26 or refer to the Toxicology and Toxinology – Therapeutic Guidelines.

Background¹

• Envenomation is rare but can be lethal
• Treat all suspected snake bites as envenomed until proven otherwise
• Apply pressure immobilisation bandage for suspected snake bites that present to Emergency if one is not already insitu.

Snake bite quick reference guide
All patients are treated as if they are potentially envenomated until proven otherwise. This takes over 12 hours to evaluate. Determination of snake type is dependent upon the geographical location, physical signs and laboratory findings.
First aid Ensure pressure bandage with immobilisation (PBI) is applied.	Transport to a hospital with: Doctor who can manage the snake bite Laboratory who can operate within 24 hours Antivenom available
Resuscitation - if collapse, seizure, major haemorrhage or cardiac arrest Manage as per the ED Guideline: Serious illness Call WA Poisons Information Centre on 13 11 26, and prepare for antivenom administration
Assessment	Signs and symptoms of envenomation
Time of bite Geographical location – near fresh water? Location of bite on the person/ number of bites Time PBI applied Signs and symptoms of envenomation	Systemic – nausea, vomiting, diarrhoea, abdominal pain, headache Hypotension Bleeding – IV site, mucosal Descending flaccid paralysis – early signs are ptosis, diplopia, blurred vision, difficulty swallowing and altered voice. Then respiratory muscle (assess Peak Expiratory Flow Rate (PEFR) in older child) and limb weakness. Muscle tenderness and pain Bite site pain
Laboratory investigations (don't use point of care testing)
Full blood picture Coagulation profile including: Activated Partial Prothrombin Time (APTT) International Normalised Ratio (INR) D-Dimer Creatine Kinase (CK) Urea, electrolytes and creatinine Lactate Dehydrogenase (LDH)	Urinalysis Snake Venom Detection kit (SVDK) – only at the request of the Toxicologist where evidence of envenomation exists. Bite site swab preferred over urine sample.
If asymptomatic and normal initial investigations, remove PBI Repeat examination and bloods 1 hour post removal of PBI and then 6 and 12 hours post bite.
If at any stage INR > 1.3, or the patient has paralysis	If at any stage Symptoms other than paralysis OR Raised white cell count OR Raised APTT or CK > 1000U/L	If all laboratory results and examinations are normal at 12 hours
Call WA Poisons Information Centre: 13 11 26 and prepare for antivenom administration Move patient to resuscitation area to manage potential anaphylaxis Give monovalent antivenom (as guided by Poisons Information Centre) Dilute 1 ampoule in 10mL/kg of sodium chloride 0.9% and administer via IV infusion over 30 minutes Remove PBI halfway through the antivenom administration Discuss with WA Poisons Information Centre: 13 11 26 regarding post antivenom care and repeat bloods	Discuss with WA Poisons Information Centre: 13 11 26 Consider antivenom	Discharge during daylight hours

General¹

• Snakes that can be found in Western Australia include black snakes (Mulga or King Brown), brown snakes (Dugite, Western Brown), Death Adders, Tiger Snakes, Taipans and sea snakes
• Around Perth, brown snakes are found everywhere, Death Adders in the hills, brown snakes in sand and Tiger Snakes in waterways.

Assessment

• Snake bites are a time critical presentation
• Rapidly complete initial physical examination and laboratory tests.

History

• Geographical area where the patient was bitten may aid in determining the type of snake
• Appearance of snake (note: this is often unreliable)
• Time of snake bite, site of bite, number of bites
• Use of pressure immobilisation bandage and other first aid treatment prior to hospital arrival.

Examination

General

• Observations (vital signs, neurological observations and neurovascular observations of the bandaged limb)
• Mental status
• Bite site – anatomical location, appearance
• Lymphadenopathy
• Evidence of bleeding
• Cardiovascular, respiratory and neurological examinations.

Signs of envenomation

Systemic signs¹

• Neurological: headache, photophobia, irritability, confusion, seizures
• Cardiovascular: hypotension, collapse
• Respiratory: respiratory failure (due to muscle paralysis)
• Gastrointestinal tract: nausea, vomiting, abdominal pain
• Other: mild fever.

Tissue specific signs¹

Toxin type	Toxin effects	Clinical Signs	Laboratory Tests
Neurotoxins	Act on the neuromuscular junction of the skeletal muscle, causing progressive paralysis Can be pre-synaptic or post-synaptic Order of progression tends to be cranial nerve palsies → skeletal muscles → respiratory muscles	Ptosis, partial ophthalmoplegia with diplopia Dysarthria, difficulty swallowing, drooling Loss of facial expression Limb weakness
Myotoxins	Bind to muscle fibres causing destruction of muscle cells with release of myoglobin Causes muscle weakness, pain on movement Leads to secondary acute tubular necrosis and renal failure	Pain on contracting muscles against resistance Muscle weakness	CK U&E Urine positive for blood (myoglobin)
Haemotoxins	Procoagulants – cause a consumptive coagulopathy (consumption of fibrinogen, and increased fibrin degradation products (FDP), disseminated intravascular coagulation, bleeding tendency Anticoagulants – cause an anticoagulative coagulopathy without generation of FDP	Persistent ooze from the bite site or venepuncture sites Signs of cerebral irritation (intracranial haemorrhage)	Coagulation profile Fibrinogen Fibrin degredation products FBP

 

Clinical and laboratory features of snake bites¹

	Coagulopathy	Neurological – Paralysis	Rhabdomyolysis	Other
Brown Snakes: Western Brown Snake (Gwarder) Dugite	Always present	Rare	No	Renal failure uncommon Microangiopathic haemolytic anaemia Thrombocytopaenia
Black Snakes: King Brown (Mulga)	Mild (raised APTT but normal  fibrinogen)	No	Develops over hours to days	Renal failure can occur Significant local bite site pain
Tiger Snake	Always present	Slow onset over hours (pre-synaptic)	Slow onset over hours	Renal failure can occur Microangiopathic haemolytic anaemia Thrombocytopaenia
Death Adder	No	Slow onset over hours (post-synaptic)	No	Local bite site pain is common
Sea Snakes	No	Rapid onset (pre-synaptic)	Develops over minutes to hours	Renal failure can occur

Investigations

Blood tests

• Coagulation profile – INR, APTT, Fibrinogen
• Fibrinogen
• D-dimer, fibrin degredation products
• FBC
• Creatinine kinase (CK)
• Urea, electrolytes, creatinine (UEC)
• Urine microscopy – red blood cells, myoglobin.

Management²

First Aid

Do Reassure the patient Keep the patient still (bring transport to them) Immediately apply a pressure immobilisation (compression) bandage, then splint the limb Seek medical attention urgently.

Don't Wash the wound Incise the wound Suck the wound Use the tourniquet

Pressure Immobilisation Bandage To delay the lymphatic spread of toxin from the bite site by compressing the lymphatic vessels at, and proximal to the bite site Immobilise the limb to prevent “muscle pump” effect Animal studies show little movement of venom centrally if the limb is still Avoid further activity – keep the patient still Technique Apply a broad elasticated compression bandage (or crepe if unavailable) over the bite and extend it (or a 2nd bandage) as proximal as possible. Apply the same amount of pressure as one would for a sprained ankle Do not occlude the circulation Splint the limb once pressure bandage applied The pressure immobilisation bandage should not be removed until: the patient has been fully assessed in hospital and there is no evidence (clinical or initial laboratory tests) of envenomation or if envenomed – antivenom has been administered.

Initial management

• The patient must be transferred to a hospital that has a doctor able to manage snake bite, a 24 hour laboratory and adequate antivenom stocks for further management.
• Pressure immobilisation bandage removed if all tests are normal and patient remains asymptomatic. If there is clinical or biochemical evidence of envenomation, give antivenom as below.

Medications

Administration of Antivenom¹

• Refer to Toxicology and Toxinology – Therapeutic Guidelines or consult WA Poisons Information on 13 11 26.
• Type of antivenom used depends on the geographical site, clinical features and laboratory tests.
• Monovalent is always preferred to polyvalent as it is safer (fewer side effects), cheaper and specific.
• Consult the WA Poisons Information on 13 11 26 for guidance on the choice of anti-venom and need for repeat doses.
• Dilute the contents of 1 antivenom ampoule in sodium chloride 0.9% 10mL/kg to a maximum of 500mL.¹
• Administer via intravenous infusion over 30 minutes.
• Repeat bloods 6 and 12 hours after antivenom, then every 12 hours until normalised.
• Note: Dose is NOT calculated by patient weight, it is the same for all children.

Further management

Side effects of antivenom

• Usually mild reactions – erythema or urticaria
• Anaphylaxis (incidence: 1% for monovalent, 5% for polyvalent).

Management of antivenom reactions

• Stop the antivenom infusion temporarily
• High flow oxygen
• If true anaphylaxis has occurred: refer to ED guideline: Anaphylaxis
• Recommence antivenom infusion as soon as clinically possible at a slower rate.

Adjuvant therapy

Blood products

• Use of blood products is controversial – they should be reserved for life threatening haemorrhage and only given after consultation with WA Poisons Information on 13 11 26.

Tetanus prophylaxis

• Refer to Tetanus prone wounds - ED Guidelines.

Complications

Serum sickness³

• Warn all patients who have received antivenom about the possibility of delayed serum sickness and the need to seek urgent medical attention should this occur.
• May occur up to 21 days after antivenom administration, and is characterised by fever, rash, generalised lymphadenopathy, aching joints and sometimes renal impairment
• Prevention: oral steroids (Prednisolone) 1mg/kg/day for 5 days is recommended for patients who received high doses of antivenom, either as a single dose of polyvalent antivenom or multiple doses of monovalent antivenom
• Treatment: For moderate to severe cases of serum sickness, use: prednisolone 1 mg/kg (up to 50 mg) orally, daily for up to 5 days.¹

Admission criteria

• Patients are monitored in hospital with serial clinical examination and laboratory tests at at 1 hour post pressure immobilisation bandage removal, and at 6 hours and 12 hours post bite.
• If evidence of envenomation occurs at any time, administer the appropriate antivenom.

Discharge criteria

• Patients can be discharged at 12 hours post bite if there is no clinical or biochemical evidence of envenomation.
• Do not discharge at night.

Nursing

• If any systemic and/or tissue specific signs of envenomation become evident, document and report immediately to the medical team.

Observations

• Baseline observations include heart rate, respiratory rate, oxygen saturation, temperature, blood pressure, pain score, neurological observations and neurovascular observations (of the bandaged limb). Record on the Observation and Response Tool, Clinical Comments Chart and the Neurovascular Observations Chart.
• Minimum of hourly observations should be recorded whilst in the emergency department.
• Any significant changes should be reported immediately to the medical team.
• A baseline electrocardiogram (ECG) should be performed on arrival.

References

1. Murray L, Little M, Pascu O and Hoggett K. Toxicology Handbook. 3rd Edition. Chatswood, NSW: Elsevier Australia; 2015. Available from: Toxicology Handbook - ClinicalKey (health.wa.gov.au)
2. First-aid management of bites and stings. Western Australian Poisons Information Centre. October 2021. Cited 22 December 2021. Available from: 6674063A8BF94460A7EE9B5B417338EC.ashx (health.wa.gov.au)
3. Snake bite. Therapeutic Guidelines Published March 2021. Cited: 12 January 2022. Available from: Topic | Therapeutic Guidelines (health.wa.gov.au)
4. Fleisher, Gary R. Ludwig, Stephen. Textbook of Pediatric Emergency Medicine, 7th Edition. 2015

Endorsed by:	CAHS DTC	Date:	Mar 2022
		Review date:	Feb 2025

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