snake spider guidelines gl2007 006 3

Key principles

■ Snakebite is a potential medical emergency and

should always receive high priority assessment and

treatment, even if the patient appears initially well.

■ The majority of snakebites will not result in significant

envenomation and will not require antivenom.

■ Particular attention should be given to the patient

with a history of multiple bites. In most of these

cases major envenomation will occur, requiring

increased amounts of antivenom.

■ Admit all cases of probable snakebite for at least 12

hours after the bite or after removal of effective first

aid to a suitable clinical unit such as emergency, high

dependency or intensive care.

■ No patient with suspected snakebite should be

discharged in the evening or during the night or to a

situation where no other adult is able to observe the

individual over the following 24 hours.

■ Manage cases only in hospitals appropriately

equipped with laboratory facilities on-site and

adequate stocks of appropriate antivenom.

■ If the patient requires transfer to a higher level of

care then ensure this is organised early in the patients

presentation.

3.1 Snakebite envenomation

Major problems may include one or more of the

following effects of the venom (note these are principally

systemic rather than local effects):

Paralysis: blocked transmission at the neuromuscular

junction causing skeletal and respiratory muscle flaccid

paralysis, either presynaptic and/or postsynaptic. Signs

include: ptosis (drooping of upper eyelids), diplopia

(double vision), ophthalmoplegia (partial or complete

paralysis of eye movements), fixed dilated pupils,

weakness and respiratory problems.

Figure (1) Ptosis following Tiger Snake bite

Figure (2) Ptosis and partial gaze paralysis followingDeath Adder bite

Coagulopathy: cause includes defibrination with low

fibrinogen, unclottable blood but usually normal platelet

count, or direct anticoagulation, with normal fibrinogen

and platelet count. Both types cause elevated prothrombin

ratio (INR). Signs include: bleeding from bite wound,

venepunctures, rarely haematemesis and haematuria.

Figure (3) Oozing Venepuncture Site

PAGE 8 NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines

Snakebite

SECTION 3

Myolysis: caused by generalised destruction of skeletal

muscle with high serum CK (creatine kinase) and

myoglobinuria (red to brown urine testing positive for

blood; can be confused with true haematuria),

occasionally severe hyperkalaemia. Signs include: muscle

movement pain or weakness, and red or brown urine.

Figure (4) Myoglobinuria

Renal damage: primary or secondary (myolysis,

coagulopathy) acute renal failure. Signs include: oliguria

(decreased urine output) or anuria (no urine output).

General symptoms: include anxiety, headache, nausea,

vomiting, abdominal pain, collapse and convulsions.

Local symptoms: vary from minimal to obvious bite

marks, local pain, swelling, or bruising. A trivial-looking

bite site does not mean a trivial bite.

NB: Punctures or scratches may occur on the skin.

3.2 First aid

Pressure Immobilisation Bandage (PIB) and Splint:

■ Maintain airway/breathing if impaired

■ Immediately apply a broad compressive bandage to

the bite site at same pressure as for a sprain

■ Extend the bandage to cover the whole of the bitten

limb including fingers/toes

■ Splint limb and immobilise

■ Keep the patient still and bring transport to the

patient

■ Do not give alcohol, food, stimulants, or cut the

wound, or use a tourniquet.

■ DO NOT WASH OR CLEAN THE WOUND

■ Leave PIB in place until patient arrives at a place of

definitive care (hospital with appropriate antivenom etc).

■ As soon as possible after applying first aid as above,

notify the relevant doctor or hospital, to organise

medical evacuation.

■ If the snake was brought with the patient, place it in

alcohol (if practical), and ensure it goes with the

patient when evacuation occurs.

Figure (5a) Pressure immobilisation bandaging

Figure (5b) Pressure Immobilisation Bandaging

Figure (5c) Pressure immobilisation bandaging

NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines PAGE 9

3.3 Hospital cllinical assessment

3.3.1 History

1. Establish whether the patient has a

confirmed/witnessed snake bite (single or multiple)

OR were the circumstances such that a bite mighthave occurred:

2. When the patient was bitten (elapsed time)

3. Description of snake if possible (colour, length)

4. Geographic location that the incident occurred

(snakes in area)

5. Timing and type of first aid, and activity, following

the bite

6. Type and timing of symptoms, in particular:

a headache

b nausea

c vomiting

d abdominal pain

e blurred or double vision

f slurring of speech

g muscle weakness

h respiratory distress

i bleeding from the bite site or elsewhere

j passing dark or red urine

k local pain or swelling at the bite site

l pain in lymph nodes draining the bite area (axilla,

or groin),

m loss of consciousness and/or convulsions.

7. Relevant past history – specifically ask about allergy

or past exposure to antivenom, atopic (allergy)

history, renal, cardiac, or respiratory disease and

medications (eg. anticoagulants etc).

3.3.2 Presentation scenarios

■ Possible or definite snakebite.

■ The patient presents unwell, diagnosis uncertain.

There is a history of possible exposure to snakes (i.e.

walking in long grass etc), and the patient has any of

the following: loss of consciousness, convulsions,

headache, vomiting, weakness or paralysis (initially

ptosis, diplopia, slurred speech), dark or red urine,

bleeding, renal failure then consider snakebite.

■ The patient is unwell and may be envenomated.

■ The patient is well with no apparent envenomation.

3.3.2 Clinical assessment

Assess the patient for the following:

■ Evidence of a bite (if an adequate first aid bandage is

in place cut the first aid bandage away from over bite

site and the area immediately surrounding the bite)

■ DO NOT WASH THE WOUND – SWAB FOR VENOMDETECTION using the Snake Venom DetectionKit (SVDK) (refer to the SVDK section at page 11 in

these guidelines for technique of venom detection).

Examine for evidence of multiple bites, or venom

movement (eg. 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)

■ Oliguria, anuria, or myoglobinuria

■ Period of unconsciousness or fitting

■ General symptoms such as headache, vomiting,

abdominal pain, but beware of these in isolation (i.e.

anxiety reaction only). If all other clinical and

laboratory indicators are normal, such general

symptoms alone are not usually sufficient reason to

commence antivenom therapy

3.3.3 Systemic envenomation

If it is evident that Antivenom Therapy will be required

then refer to the Antivenom Administration section at

page 22 in these guidelines).

Systemic envenomation is present if there is one or more

of the following:

■ Neurotoxic Paralysis (e.g. ptosis, ophthalmoplegia,

limb weakness, respiratory effects)

■ Significant Coagulopathy (e.g. unclottable blood,

INR>2, prolonged bleeding from wounds and

venepunctures)

■ Significant Myolysis (myoglobinuria)

■ Unconsciousness or convulsions

Early non-specific symptoms such as headache, vomiting,

abdominal pain may indicate developing envenomation.

Beware of these as purely manifestations of anxiety

rather than envenomation. If these are the only evidence

of envenomation then be cautious in deciding if

antivenom is required.


3.4 Snake Venom Detection Kit (SVDK)

The SVDK is designed to detect very small amounts of

snake venom, and indicate which type of venom is present,

corresponding to one of the 5 monovalent antivenoms. It

does not necessarily indicate if envenomation has occurred.

Specifically:

■ Only use the SVDK to choose which antivenom is

appropriate

■ Do not use it to determine if there is envenoming, or

exclude snakebite

■ The best sample is a bite site swab (pre-moistened in

supplied SVDK fluid):

– Cut away bandage over bite site and swab for

venom detection

– Collect at earliest opportunity after presentation

to hospital

– Where systemic envenoming is evident then urine

may be used

– NB: Blood testing is unreliable

■ The test may take up to 25 minutes and is best

performed in a laboratory

■ A positive result in an envenomed patient indicates a

definite snakebite and the type of antivenom to use

(if required)

■ A positive SVDK is not the sole indication to give

antivenom

■ Administer antivenom if there is clinical and/or

laboratory evidence of significant systemic

envenoming indicated by the clinical signs and

symptoms listed

■ NB: Positive venom detection from the bite site does

not imply systemic envenoming and is not in itself an

indication for antivenom

■ A negative result does not exclude either a snakebite

or systemic envenoming

■ Always confirm the SVDK result by comparing with

result from diagnostic algorithms as outlined in Figure

(12) combined with knowledge of snakes in region

3.4.1 Snake venom detection kit testing

The SVDK comes in a kit including three separate test

well strips, each in protective foil, but only one set of

instructions, reagents and accessories. It must be kept

refrigerated, though if in a lab at 22ºC, it can be left out

of the fridge for the 20–25 minutes required to perform

the test.

Figure (6) Snake Venom Detection Kits

1. The best sample is a swab from the bite site. Take an

unused sample diluent bottle (currently yellow top)

and use fingernail to lever off the dropper cap.

2. Moisten the swab stick provided, in the solution in

the bottle. Rub the swab firmly over the bite site and

adjacent skin.

Figure (7) Swab bite site and adjacent skin

3. Place the end of the swab back in the bottle

containing solution and twirl around for a few

moments to transfer venom into solution. Then

proceed to use the kit as indicated in the instructions.

4. A positive result is indicated by a colour change (to

blue) in one of the first five wells, plus the positive

control well (well 7), within 10 minutes in the last

stage of the test. Observe all tubes carefully

throughout this last 10 minute period to identify the

first well to change colour. If one tube changes

colour, all will do so eventually, but only the first tube

to change is relevant.

Figure (8) Positive venom detection


5. A positive result usually indicates that:

■ venom was present on the skin

■ the type of snake involved

■ the appropriate monovalent antivenom to use should

this be needed

6. A positive SVDK result does not indicate systemic

envenomation and is not an indicator for antivenom

therapy.

7. A negative SVDK result does not exclude snakebite

(see these Guidelines on each type of snake for

further guidance on interpretation).

8. Be aware that false positives from bite site swabs,

though rare, are possible.

9. If the patient has evidence of systemic envenoming

and the bite site is not available for testing (i.e. been

washed, or not apparent), then URINE is worth

testing for venom. See kit instructions for dilutions, if

necessary. Do not test urine unless the patient has

evidence of systemic envenoming. Do not try and use

the SVDK to test on urine as a method of proving or

excluding snakebite. Urine can give false positives for

venom, especially brown snake venom. A positive SVDK

result for brown snake venom, in the absence of

clinical or laboratory evidence of envenoming, such

as coagulopathy, in nearly all cases should be

considered a false positive and therefore of no

diagnostic value.

10.Blood has proved an unreliable sample for venom

testing with the SVDK, giving both false positives and

false negatives. It is not recommended for use with

the SVDK.

11.The SVDK should not be used to determine if a

snakebite is a likely diagnosis. The only purpose ofthe SVDK is to determine best choice ofantivenom, should antivenom be indicated onclinical or laboratory grounds.

Figure (9) Snake/well correlation

Well 1 Tiger Snake Venom

Well 2 Brown Snake Venom

Well 3 Mulga Snake Venom

Well 4 Death Adder Venom

Well 5 Taipan Venom

Well 6 Negative Control

Well 7 Positive Control

Well 8 Blank Well


Weak positive well 1 (cross-linkage effect, not relevant)

Strong positive well 3 = mulga snake

Weak positive well 5 (cross-linkage effect, not relevant)

Negative control well (6)

Positive control well (7)

Figure (10) Actual SVDK result in a case of Mulga Snake bite — CSL Snake venom detection kit

Figure (11) Common patterns of SVDK venom detection results


Well number:

1 2 3 4 5 6 7 8

Diagnostic pattern:

Only well 7 positive: No snake venom detected.This result does not include snakebite.

Wells 7 and 1 positive: If systemic effects includedefibrination, paralysis ± myolysis, suggests Tiger Snake orRough-scaled Snake bite. If systemic effects defibrination only, consider bite by Broad-headed, Pale-headed or Stephen’s Banded Snake. If systemic effects are confined to paralysis, without defibrination, consider possibility of Copperhead Snake.

Wells 7 and 2 positive: Most likely a Brown Snake bite. If systemic envenoming develops, expect defibrinationcoagulopathy, ± renal damage. Paralysis is unlikely andmyolysis should not occur.

Wells 7 and 4 positive: Death Adder bite. If systemic envenoming develops, expect post-synaptic paralysis, no coagulopathy, significant myolysis or renal damage.

Wells 7 and 5 positive: Taipan or Inland Taipan bite; systemic envenoming very likely. Expect defibrination, coagulopathy, paralysis, ± myolysis, ± renal damage.

Wells 7, 1 and 3 positive: This pattern is sometimes seenwith bites by several species. With a Copperhead bite, if there is systemic envenoming, expect paralysis withoutcoagulopathy. If a Red-bellied or Blue-bellied (Spotted) Black Snake bite, if there is systemic envenoming, expect only mild myolysis, no coagulopathy, paralysis or renal damage. If a Collett’s Snake bite, if there is systemic envenoming, expect myolysis, possibly anticoagulant coagulopathy, ± renal damage.

Wells 7 and 3 positive: Most likely a bite by a Mulga Snake (King Brown) or Collett’s Snake. If systemic envenoming, expect myolysis, extensive swelling of bitten limb, ± anticoagulant coagulopathy, ± renal damage, OR possibly a bite by a Red-bellied or Blue-bellied (Spotted) Black Snake. If systemic envenoming, expect only mild myolysis, no coagulopathy, paralysis or renal damage.

Figure (12) Methods for determining type of snake if venom detection is not available or has failed


Determining the most likely snake based on clinical findings

Start here Local effects of bite

Examine the bite site

Minimal local effects, no significantredness, swelling, bruising

Obvious redness, swelling, ± bruising

Moderate to severelocal pain

Minimal or no local pain

Marked swelling after3+ hours

Only mild swellingafter 3+ hours

• ? Death Adder• Brown Snake• ? Taipan

• Mulga Snake• Red-bellied Black Snake• Yellow-faced Whip Snake

• Tiger Snake• Rough-scaled Snake• ? Taipan

Please note: This chart cannot cover all possible situations and assumes an understanding of the symptoms and signs of local, general and specific envenoming by Australian snakes. If in doubt, seek advice from the Poisons Information Centre (131 126) and from your local Critical Care Referral Network. © 1998 Dr Julian White

Combine this information with the result of the systemic effects key (below) to give a best guided estimate for the type of snake most likely to have caused the bite. Accuracy can be improved by matching this with known snake fauna for the region where the bite occurred.

Yes

Yes

Yes

Yes

Yes

No

No

NoNo

NoNo

Is there a coagulopathy?

Is there paralysis?

Defibrinationcoagulopathylow fibrinogenraised FDP/XDP

Anti-coagulationnormal

fibrinogenand FDP/XDP

Is there paralysis± myolisis?

Is thereparalysis?

• Brown Snake• Broad-headed Snake or Stephen’s Banded Snake

• Tiger snake• Rough-scaled snake• ? Taipan

• Mulga Snake• Spotted Black Snake• Collett’s Snake

• ? Death Adder• ? Copper- head

• Mulga Snake• Spotted Black Snake• Collett’s Snake• Small-eyed Snake

• Red-bellied Black Snake• Yellow-Faced Whip Snake

Is there majormyolysis?

Is there majormyolysis?

Systemic effects of bite

3.5 Laboratory evidence of envenomation

Laboratory testing in cases of possible snakebite is crucial

in diagnosis and is urgent. Any delay in delivering results

may delay definitive and life saving treatment. Frequent

repeat testing is almost always required. This is to ensure

that delayed envenoming or failure to respond to initial

treatment is not missed.

3.5.1 Laboratory testing

■ Laboratory tests to monitor for envenoming should

include coagulation studies (INR, aPTT, fibrinogen,

d-dimer), FBC/CBP (including blood film examination

for schistocytes), EUC and CK. (Where direct

fibrinogen testing is possible, down to very low levels

of fibrinogen, this is also a useful test).

■ If initial tests are normal, repeat testing at least twice,

at approximately 2–3 hour intervals, or more urgently

if the patient develops clinical evidence suggestive of

envenoming.

■ Where laboratory testing is not rapidly accessible a

whole blood clotting time (WBCT) may be performed

but should not delay arrangements for transfer of the

patient. (WBCT – put 10 ml venous blood into a glass

test tube and measure time taken to clot – normal

less than 10 mins).

■ An INR>2 indicates a coagulopathy (unless the

patient is on Warfarin).

■ Myoglobinuria or a significantly raised CK indicates

myolysis.

■ Abnormally raised creatinine or urea indicates renal

damage.

■ Cut away the bandage over bite site and swab for

venom detection (CSL Snake Venom Detection Kit).

■ The best sample for venom detection is a bite site swab.

3.5.2 Clinical and laboratory profiles following Australian snakebite

1. Defibrination coagulopathy

No paralysis or myolysis. The bite site usually has minimal

or no pain, no significant swelling, bruising or redness,

but there may be ooze of blood. Likely snakes include:

■ Brown Snakes (all species except Ringed Brown

Snake) (Genus Pseudonaja)

■ Broad-headed Snakes, including Stephen’s Banded

Snake and Pale-headed Snake (Genus Hoplocephalus)

2. Defibrination coagulopathy + paralysis ± mildmyolysis

Bite site is variable and there may be an ooze of blood.

Likely snakes include:

■ Taipan and Inland Taipan (Genus Oxyuranus).

3. Defibrination coagulopathy + paralysis +moderate to severe myolysis

Bite site is usually painful with mild swelling, bruising,

redness, and there may also be an ooze of blood. Likely

snakes include:

■ Tiger Snakes (Genus Notechis)

■ Rough-Scaled Snake (Genus Tropidechis)

4. Moderate to marked myolysis + anticoagulantcoagulopathy (fibrinogen normal, no raisedFDP/XDP)

No paralysis (beware major myolysis mimicking paralysis).

Bite site is usually painful, often with marked swelling

and sometimes bruising. Persistent blood ooze is not

common. Likely snakes include:

■ Mulga snake, Collett’s snake, Spotted black snake

(Genus Pseudechis).

5. Moderate to marked myolysis

No paralysis (beware major myolysis mimicking paralysis)

or coagulopathy. Bite site is usually painful, has marked

swelling and sometimes bruising. Persistent blood ooze

not common. Likely snakes include:

■ Mulga snake, Collett’s Snake, Spotted Black Snake

(Genus Pseudechis).

■ Eastern Small-Eyed Snake (Rhinoplocephalus

nigrescens).

6. Paralysis (postsynaptic: reverses with antivenomtherapy) ± mild anticoagulant coagulopathy

No myolysis and renal damage unlikely. Bite site is often

painful, but with little swelling, redness or bruising.

Persistent blood ooze unlikely. Likely snakes include:

■ Death Adders (Genus Acanthophis).

7. General symptoms of envenomation (some or allof: headache, nausea, vomiting, diarrhoea,abdominal pain, dizziness, collapse).

No paralysis or coagulopathy with no, or generally mild,

myolysis. Bite site is usually painful with marked swelling

and sometimes bruising. Persistent blood ooze not

common.


Likely snakes include:

■ Red-bellied Black Snake (Pseudechis porphyriacus)

and mild bites by Spotted Black snake and Collett’s

Snake (Genus Pseudechis).

■ Yellow-faced Whip Snake and other large Whip

Snakes (Genus Demansia).

3.6 Essential information for hospitallaboratory staff

Details of venom actions and venom profiles for each

major snake species are contained in these guidelines and

should be referred to when interpreting laboratory results.

3.6.1 Required laboratory testing

1. Coagulation Studies: PT/INR, aPTT, fibrinogen level,

d-dimer/FDP, platelet count (Where direct fibrinogen

testing is possible, down to very low levels of

fibrinogen, this is also a useful test).

a. Defibrination-type coagulopathy (BrownSnakes,

Tiger Snakes, Rough-scaled Snake, Taipans, Broad-

headed Snake group).

■ Characterised by grossly prolonged PT & aPTT,

undetectable fibrinogen, grossly elevated d-dimer/

FDP, platelets normal (sometimes slightly low).

■ Some coagulation machines will have trouble

giving results in this situation. If the machine

indicates gross prolongation of PT/aPTT, but

fibrinogen “very high”, this usually indicates

undetectable fibrinogen.

■ If d-dimer/FDP is elevated, you can be sure

fibrinogen will be very low, not very high. As soon

as such a picture is evident, immediately report

this to the treating doctor.

■ Do not delay while trying to get final results from

the machine. Similarly, if d-dimer/FDP is elevated,

report this first, then go back and determine the

actual level, which may take time.

■ Do not waste valuable time retesting and calling

for new specimens because the machine cannot

cope with the grossly abnormal results. Snakebite

coagulopathy is common and time is of the

essence. So, look for the typical defibrination

picture and report this as soon as it is clear that it

is present. Be aware that in mild cases, in the

early stages, PT/INR and aPTT may be normal,

fibrinogen level normal or only slightly decreased,

but d-dimer/FDP will be elevated.

■ This is an important indication of possible

developing coagulopathy. However, a similar

picture is present in a patient with venous

thrombosis problems, so careful clinical judgement

will be required by the treating doctor, to decide

which is the more likely diagnostic explanation.

b. Anticoagulation-type coagulopathy (Mulga

Snakes, Collett’s Snake).

■ Characterised by mild to grossly prolonged PT and

aPTT, but normal fibrinogen levels and no significant

elevation of d-dimer/FDP.

c. Patients on Warfarin and similar anticoagulants

■ These patients may present a problem in interpreting

results, if bitten by a snake. Warfarin should cause

prolongation of PT in particular, sometimes with

elevated d-dimer/FDP, but normal fibrinogen. If

snakebite defibrination coagulopathy is overlaid

on this background, in most cases, fibrinogen will

be depleted and d-dimer/FDP grossly elevated, with

an INR of >4, usually >10 (actually infinity). This

should not cause confusion in interpretation, as

such a pattern is clearly not due to Warfarin, but a

result of envenoming.

■ This pattern may be complicated by the fact that

warfarin causes low levels of factors, which the

toxins need to act on, leading to different

pharmacodynamics.

■ In cases with early or mild snakebite defibrination

coagulopathy, changes may be subtle. In this

setting, significant elevation of d-dimer/FDP may be

the most important diagnostic clue that envenoming

is occurring. In cases of snakebite anticoagulation-

type coagulopathy, interpretation may be more

difficult, as elevation of d-dimer/FDP is not a feature.

In this setting coagulation tests may not give clear

cut evidence of envenoming. Fortunately, in these

cases, clinical features and rising CK are likely to

assist in diagnosis of envenoming.

2. Complete blood picture (Platelets, Hb, WCC,

absolute lymphocyte count, including blood film

examination for schistocytes).

a. Acute systemic envenoming usually causes an

elevated WCC

b. There may be an associated absolute lymphopenia,

which can be quite marked

c. Lymphopenia is always present in tiger snake bites

with systemic envenoming, but is less consistent for

other snake species


d. Thrombocytopenia is not a common acute feature of

envenoming and when present, is often associated

with renal damage

e. In rare cases, especially with Brown Snake bite, a

thrombocytopenia like picture may develop, often

after the initial defibrination coagulopathy is

responding to antivenom. In such cases there will be

a falling Hb, falling platelet counts, rising creatinine

and urea, and usually schistocytes on the blood film.

3. Muscle Function (CK)

a. A number of snakes can cause moderate to severe

systemic muscle destruction (myolysis) including

Mulga Snakes, Collett’s Snake, Tiger Snakes, Rough-

scaled Snake, Taipans and Black Snakes).

b. This may take several hours to become evident,

occasionally days.

c. Clinically the patient develops muscle pain, weakness

and myoglobinuria. At a lab level, CK can become

grossly elevated.

d. Significant myolysis is associated with CK levels

>1,000 IU/L and can exceed 100,000 IU/L (sometimes

far higher than this). In such cases beware associated

hyperkalaemia that can cause lethal cardiac toxicity.

e. Measurement of serum or urine myoglobin levels does

not add to the diagnosis, is expensive, and treating

doctors should be encouraged to use CK levels as the

indicator of myolysis rather than myoglobin levels.

4. Renal function (creatinine and urea)

Snakebite can cause renal damage and occasionally renal

failure, often secondary to coagulopathy, myolysis, or

hypotension. In mild cases, especially with brown

snakebite, there may be a slow rise in creatinine and

urea over the first few days, without polyuric or anuric

renal failure, which will reverse and gradually improve

over a week or so. However, rising creatinine and urea

should always be flagged, as it may indicate progression

to major renal failure.

5. Electrolytes

Hyperkalaemia is the major risk, most often in

association with myolysis and secondary renal failure.

However, hyponatraemia can also develop, most likely in

response to over vigorous IV fluid replacement.

6. Liver function tests

a. LFTs are not routine tests in snakebite cases.

Temporary elevation of LFTs sometimes occurs but is

rarely of clinical significance

b. There is no defined picture of envenoming-induced

liver damage in humans. However, LDH is a useful

test in patients with haemolysis, either in Brown

Snake bites that develop microangiopathic haemolytic

anaemia or in Black Snake where direct toxin

mediated haemolysis may occur.

3.2.1 Derived fibrinogen (important considerations)

Derived fibrinogen is merely a reflection of the PT and as

such adds nothing more than a pseudo PT and is not as

sensitive as a direct Fibrinogen (Clauss). This is poorly

recognised with many laboratories not clearly

distinguishing derived vs direct (Clauss), while others

report both derived and Clauss.

Furthermore, there is a limit of quantification/reporting

for Clauss fibrinogen, because this differs on machines

and most importantly in the way they are reported or

understood by the laboratory staff.

Some analysers will only allow results such as <0.65, and

it is impossible to get anything lower. This is not very

sensitive because by the time the Fibrinogen is above

0.65 the PT/aPPT have usually started to recover.

In some laboratories the limit of quantification is <0.5,

however they will often report 0.2 or 0.3 but say it is

below the limit of quantification (not detection) so they

can’t guarantee the difference.

This is an important difference in those reports below

the LOQ and the LOD, which may not be clear to some

laboratories.

The issues around low levels of Fibrinogen are complex,not necessarily well understood and are often limited bythe analyser only reporting <LOQ. This is primarily due tothe broad acceptance that a Fibrinogen <1.5 is low andoften associated with significant haematologicalabnormality. However, treated snake bite patients havevery low Fibrinogens which are actually recovering, buttake time to get >1.5. For these patients it is importantto know that the Fibrinogen is just detectable.

It is also common to find a “near normal” PT/aPTT whenthere is still a low Fibrinogen around 0.5 – 0.9. This is aproblem for the analyser and may not be understoodwell by Haematologists who are not familiar with resultsdemonstrating a slightly raised INR and a low Fibrinogen.

It is suspected, but not yet proven, that in snake bite thePT is driven by factor V deficiency (and also factor VIII),and not so much by fibrinogen – the former recoversmore rapidly, which is manifested by a normalisation of


the PT and a gradual recovery of fibrinogen. This is likelyto be the main driver for the use of Fresh Frozen Plasma(FFP) in these situations.

Given the complexity of interpreting derived Fibrinogen

and very low Fibrinogen levels in these patients, it is

strongly recommended that early expert advice be

obtained in the first instance through the PoisonsInformation Centre on phone 131126.

3.7 Hospital clinical management

Venomous snakebite is a medical emergency, potentially

life threatening, and is not a simple matter of just giving

antivenom. Expert advice is available from the PoisonsInformation Centre on phone 131126 and through

the local Critical Care Referral Network.

A considerable number of snakebites do not result in

significant illness, and do not require antivenom, but all

probable snakebites should be admitted for observation

for at least 12+ hrs or overnight, as some serious effects

may be delayed.

Following the immediate clinical management, the

definitive clinical management will be dependant upon

whether or not the health facility has antivenom stocks

immediately available.

3.7.1 Immediate clinical management

■ Assess and maintain airway

■ 100% Oxygen

■ Respiratory support as indicated

■ Establish intravenous access and administer

intravenous fluids (fluid load)

■ Commence serial clinical observations and serial

laboratory testing. If clinical (including antivenom

stocks) or laboratory facilities are inadequate,

maintain pressure immobilisation bandage and

arrange retrieval to an appropriate hospital

■ Antivenom therapy is indicated in most cases if there

is any evidence of systemic envenoming detected by

clinical observation or on laboratory testing

■ Consult early with the local Critical Care Referral Network,

Clinical Toxicologist and the Poisons Information

Centre preferably before commencing antivenom

■ Removal of pressure immobilisation bandage:

– The bandage should not be removed until the

patient is fully assessed (clinical history,

examination, laboratory tests performed and

results assessed, venom detection performed and

result obtained), stabilised (ABC, IV line in situ, IV

fluid load) and if envenomed, treatment commenced

(appropriate type and dose of IV antivenom given).

– In a significant number of patients, initial clinical

and laboratory examination will be normal, with

no indication of systemic envenoming. Such

patients do not require antivenom at this time

and the pressure immobilisation bandage first aid

should be removed.

– The patient should then be fully re-evaluated

within 2 hours (including repeat laboratory

testing) or earlier if symptoms develop.

– Do not leave pressure immobilisation bandage in

place for long periods of time, especially in an

asymptomatic patient.

3.8 Clinical management of definiteor probable snakebite in a hospitalwithout antivenom available

Where the patient presents with a definite or possible

snakebite.

1. If not already applied, immediately apply correct first

aid, namely a broad compressive bandage bound first

over the bite site, at the same pressure as for a sprain

(i.e. not so tight that it occludes the blood supply),

then bind the bandage over as much of the bitten

limb as possible, going over the top of clothing, and

keeping the limb as still as possible.

2. Once the limb is bandaged then immobilise it using a

splint and keep it in a neutral position (not elevated

or below the patient).

3. Do not wash the wound, but if a venom detection kit

is available then swab the wound prior to applying

first aid, but do not delay first aid significantly just to

swab for venom, unless the patient appears well and

greater than 20 minutes has elapsed since the bite.

4. Keep the patient as still and quiet as possible.

5. Fast the patient, and be prepared for vomiting.

6. Carefully watch for evidence of envenoming, and if

there is respiratory distress then provide respiratory

support.

7. Monitor urine output and colour.

8. If the snake was brought with the patient, place it in

alcohol (if practical) and ensure it goes with the

patient when evacuation occurs.


9. As soon as possible after applying first aid as above

and notify the relevant doctor or hospital to organise

medical evacuation. It will assist the retrieval team if

you can give the following patient status report:

■ Name, sex, age of patient

■ Brief history of the suspected bite

■ Was a snake seen?

■ What type of snake?

■ Was it a multiple bite?

■ Are there any symptoms or signs of envenomation?

(Namely: headache, nausea, vomiting, abdominal

pain, collapse, convulsions, early paralysis such as

drooping upper eyelids, double vision, slurred

speech, limb weakness, evidence of bleeding

problem such as persistent ooze from the bite

site, evidence of muscle damage such as dark or

red urine, muscle pain).

■ Patient’s past history, particularly past snakebites

with antivenom therapy, allergic disease, renal or

heart disease, or use of anticoagulant drugs

(e.g. warfarin) or anti-platelet drugs (e.g. aspirin

or NSAIDS).

3.9 Clinical management of definiteor probable snakebite in ahospital with antivenom available

3.9.1 Respiratory failure

Artificial ventilation – mouth to mask; bag/mask,

bag/endotracheal tube as indicated.

3.9.2 Circulatory failure

1. If cardiac arrest – commence cardiopulmonary

resuscitation.

2. Insert an IV line (normal saline, give initial IV fluid load,

500 – 1000ml over 2hrs in adults, 20ml/kg for children,

then run at maintenance, keep the patient fasted).

3. If possible insert long line in cubital fossa or similar,

to allow frequent blood sampling and avoid the need

for further venepunctures.

4. Avoid subclavian, femoral and jugular vessels, as

uncontrollable haemorrhage may occur if there is a

coagulopathy.

5. If profound hypotension – fluid and electrolyte

resuscitation.

6. A degree of hypertension may be encountered which

usually resolves.

If patient already has severe envenomation then apply

pressure bandage/ immobilisation first aid if not in situ

(remove only when initial antivenom therapy is completed).

3.9.3 Blood samples

1. Whole blood clotting time (in glass test tube)

2. Coagulation studies (PT/INR, aPTT, Fibrinogen, XDP/d-

dimerFDP) full blood profile (CBP/FBE including blood

film examination for schistocytes) (Where direct

fibrinogen testing is possible, down to very low levels

of fibrinogen, this is also a useful test)

3. Electrolytes, renal function, CK

4. Avoid venepuncture in sites where bleeding may be

difficult to control (i.e. femoral, neck, subclavian)

3.9.4 Anaphylaxis

Anaphylaxis due to allergy to venom is occasionally seen:

(i.e. in reptile keepers). Treat with IV Adrenaline infusion or

IM Adrenaline (initial dose 0.25–0.5 mg.). For suggested

paediatric dosages and further information, refer to the

relevant section in these guidelines.)

3.9.5 Ongoing care

1. Observe closely for evidence of developing paralysis

(ptosis and diplopia).

2. Monitor urine output – indwelling catheter as

necessary.

3. Serial respiratory function (FVC, O2 saturation and/or

expired CO2).

4. Check and update Tetanus immunisation status (once

coagulopathy has resolved).

5. Avoid unnecessary venepunctures.

6. Once the patient is stabilised the pressure.

immobilisation bandage may be removed however, if

the patient has a severe envenomation and requires

transfer to another hospital and/or if there will be a

delay in obtaining further supplies of antivenom,

consider leaving the pressure immobilisation bandage

in situ.

7. If left in situ, then regular limb circulation

observations should be performed.


Figure (13) Snakebite management chart


Patient presents with possible snakebite

Patient is severely envenomed, i.e. hasone or more of: collapse/unconscious,paralytic signs, coagulopathy, myolosis

Please note: This chart cannot cover all possible situations and assumes an understanding of the symptoms and signs of local, general and specific envenoming by Australian snakes (see Section 4: Snakebite, and preceding pages). If in doubt, seek advice from the Poisons Information Centre (131126) and from your local Critical Care Referral Network. © 1998 Dr Julian White

Patient is symptom-free, or has only mildor general symptoms, i.e. has one or more of:headache, nausea/vomiting, abdominal pain

FIRST AIDPatient has had correct

first aid appliedi.e. PIB

FIRST AIDNo effective first aid

has been appliedAPPLY PIB first aid

FIRST AIDPatient has had correct

first aid appliedi.e. PIB

FIRST AIDNo effective first aid has been

applied DO NOT APPLYnow if >1hr post-bite

Leave PIB in place until patient is stabilised,fully assessed, and antivenom given (if required)

Repeat blood tests at 3 hrs and 6 hrs post AV

Coagulopathy is resolving (rise in fibrinogen/reduction

in whole bloodclotting time)

Coagulopathy not resolving(no rise in fibrinogen/

grossly prolonged wholeblood clotting time

Develops or has significantsymptoms or signs or

abnormal blood tests, i.e. paralytic signs, coagulopathy,

myolysis, renal impairment

Remains symptom-free orminor general symptoms only(i.e. headache, nausea etc)and blood tests are normal;

do not give antivenom

Remove first aid once IV lineinserted, venom detection*and blood tests performed

and reported as normal

TREATMENT: Continue tomonitor closely; repeatblood tests to ensure

continuing improvement

TREATMENT: Once recovered, send home but follow up for serum sick-

ness. Consider prophylacticoral steroids for 1 week.

TREATMENT: Give moreantivenom IV, diluted,

adrenaline ready (in case ofanaphylacticoid reaction

TREATMENT: Give appropriateAntivenom IV, diluted,

adrenaline ready (in case ofanaphylactoid reaction

TREATMENT:Admit overnight. If remains

well, repeat blood tests next morning and ifnormal, send home.

TREATMENT:Check patient for signs of

envenoming frequently andrepeat blood tests after

about 2 hrs, then 2–3 hrs later

TREATMENT• Attend to ‘ABC’ but be careful of causing bleeding.• Insert IV line, given IV fluid load.• Take blood for lab tests* and swab bite site for venom detection** collect urine and check for haemoglobin/myoglobin (dip stick) and keep bite site swab for venom detection• Commence IV antivenom (use Polyvalent or mixture of monovalent AVs if snake identity is uncertain; do not delay giving AV by waiting for venom detection results)• Consider giving increassed starting doses of antivenom• Monitor fluid balance, catheterise if in doubt about urine output.

Patient discharged home

FIRST AID FOR SNAKE BITEPIB = Broad bandage over

bite site, then rest of bitten limb,including toes/fingers, at same

pressure as for ankle sprain,then splint limb, keep immobile.

Leave PIB first aid in placeuntil patient is stabilised

and antivenom given

Remains symptom-free or minor general symptoms only (i.e. headache, nausea etc) and blood tests are normal; do not give antivenom

*Laboratory testsCoagulationIf no lab quickly available:• Whole blood clotting time (QBCT) (5–10 ml venous

blood in glass test tube. Measure time to clot; >10 mins suggests coagulopathy but test staff member’s blood as normal control.

If lab available, request:• Prothrombin time/ INR • aPTT • FDP/XDP (d-dimer) • CBP/FBE (platelet count and blood film for schistocytes)Other• Creatinine and urea • Electrolytes (especially K+)• CK for myolysis • CBP/FBE (WCC for leukocytosis ± lymphopenia

• Insert IV line, given IV fluid load. • Take blood for lab tests. * • Cut away first aid bandage (if present) over bite site and swab bite site for venom detection. ** • Collect urine and check for haemoglobin/myoglobin (dip stick) and keep for for venom detection. • Secure supply of antivenom (use Polyvalent AV or a mixture of monovalent AVs if snake identity uncertain• Monitor fluid balance, consider catheterising if in doubt about urine output.

TREATMENT

SVDK SNAKE VENOM DETECTION KIT**Cut away first aid bandage over bite site only, to allow visual access and swab for venom detection. NOTE: bite site swab is best sample. Only test urine if no bite site

available AND patient has systemic envenoming. DO NOT use SVDK to determine if patient has snakebite.

3.11 Antivenom therapy

Antivenom is the definitive treatment of envenomation,

potentially life saving and is produced using refined

horse serum therefore it is potentially allergenic and as

such its use is not without risk. Therefore, antivenom

should only be used if there is systemic envenoming.

Overall, less than 1 in 4 patients require antivenom therapy.

3.11.1 Key antivenom therapy principles

■ The treatment of choice for systemic envenoming is

to use a monovalent (specific) antivenom in

preference to polyvalent antivenom if the identity of

snake is known.

■ Use the SVDK in conjunction with the diagnostic

algorithms along with consideration of the type of

snakes found in region to determine the most

appropriate antivenom therapy.

■ Consult with the NSW Poisons Information CentrePh: 131126 if unsure or if there is a conflict between

the SVDK and diagnostic algorithm results.

■ Do not overlook polyvalent antivenom as backup if

insufficient monovalent antivenom available.

■ 1 vial of CSL Polyvalent Snake antivenom isequivalent to 1 vial of relevant monovalentantivenom.

■ Dosage varies with the type of antivenom, type of

snake and number of bites however, childrenrequire the same dose as adults.

■ Further doses of antivenom may be required in major

cases.

3.11.2 Snake identified

Monovalent Antivenom is preferred to Polyvalent as it is

less hazardous and has fewer side effects, and is less

expensive. Refer to the relevant section on specific snake

management, in these guidelines, for the appropriate, safe

and effective administration of antivenom therapy. It must

be noted that bites by some snakes may not need anti-

venom even if there is mild to moderate envenoming.

3.11.3 Snake not identified

Where an SVDK is not available, or failed, or the patient

requires antivenom before a SVDK result is possible, then

either Polyvalent Antivenom or an appropriate mixture of

Monovalent Antivenoms should be used. Diagnostic

algorithms (Figure 12, page 14) may assist in choice of

antivenom. Refer to Appendix (1) to determine if there is

an appropriate mix of two monovalent antivenoms for

your area. In general terms, in eastern NSW, a mixture of

CSL Tiger Snake Antivenom and CSL Brown Snake Anti-

venom will often be appropriate, providing a bite from a

Death Adder can be excluded on grounds of description

of the snake. However, there are areas where such a mix

will not be sufficient, such as far North-Eastern NSW

where there is a chance of Taipans being present.

3.12 Antivenom therapy dose

The minimum dose is one vial of the appropriate

antivenom however for some antivenoms the initial dose

is higher.

Multiple bites or severe envenoming mandate higher

doses; increase the dose by 1 to 3 vials, depending on the

type of antivenom, and be prepared to give more. Four

to 6 or more vials is not unusual in a severe snakebite.

If there is a coagulopathy then the dose can be titrated

against serial coagulation results (see relevant section in

these or guidelines for managing coagulopathy).

3.12.1 Brown Snake

The starting dose for severe Brown Snake envenomation

is currently being investigated by a national multi-centre

prospective trial. The initial dose may range from 2 to 5

vials.

In small remote centres, the current recommended initial

dose in a life-threatening situation is 2 vials. Organise

medical retrieval as early as possible for the patient to be

immediately transferred to the closest Rural Referral

Hospital for ongoing management and additional doses

as required.

In Rural Referral and Tertiary Referral Hospitals sufficient

antivenom stocks will be available to give additional doses

as required and replenish stocks at the small remote centres.

As dosing recommendation may evolve with time,

consultation with a clinical toxicologist via the New

South Wales Poisons Information Centre Phone131126 is recommended in all cases.

3.12.2 Tiger Snake

Starting dose for a major bite is 4 vials of CSL Tiger

Snake Antivenom.

For some smaller rural hospitals, the recommended stock

level is only 2 vials, to be given in life-threatening

situations, whilst supplementation of stocks from another

hospital, plus medical retrieval, are being arranged.


3.12.3 Taipan Snake

Starting dose for a major bite is 3 vials of CSL Polyvalent

or 3 vials of Taipan Antivenom.

3.12.4 Mulga Snake

Starting dose for a major bite is 1 vial of CSL Black Snake

Antivenom or 1 vial Polyvalent Antivenom.

3.12.5 Red-bellied Black Snake

Starting dose for a major bite is 1 vial of CSL Tiger Snake

Antivenom (not Black Snake Antivenom).

3.12.6 Death Adder

Starting dose for a major bite is 1 vial of CSL Polyvalent

or 1 vial Death Adder Antivenom.

As dosing recommendation may evolve with time,

consultation with a clinical toxicologist via the NewSouth Wales Poisons Information Centre, phone131126 is recommended in all cases.

3.13 Antivenom administration

Prepare the patient and clinical environment for potential

anaphylaxis or anaphylactoid reaction to antivenom.

3.13.1 Preparation prior to commencing antivenom

1. High flow oxygen.

2. Dedicate one small bore (18–20g in adults) IV line to

antivenom administration, and one large bore IV line

(16–14g in adults) for emergency resuscitation

(equivalent size suitable for children).

3. Prepare 1L Normal Saline (20 mL/kg in children) ready

to give under pressure.

4. Prepare adrenaline 1:1000 (1 mg in 1mL) drawn up to

a dose of 0.01 mg/kg (max. 0.3 mg, i.e. max 0.3 mL)

and label “Adrenaline for IM injection only (dose in mg)”.

5. Prepare an IV infusion of adrenaline 1 mg in 100mL

or as per local protocol (controlled by infusion pump

or syringe driver) ready to attach by a side arm to the

resuscitation line. Anti-reflux valves must be attached

above the side arm on any other infusions using this

IV, to prevent adrenaline going back up into the other

fluid bags. To prevent erroneous administration, do

not attach the adrenaline infusion unless it is needed.

6. Continuous monitoring of vital signs including ECG,

Pulse, BP and Sa02%.

7. Record blood pressures on the other side to the

fluid/adrenaline infusion, to avoid prolonged cuff

inflations and thus extravasation of infusion fluids.

3.13.2 Administration method

1. Antivenom for snakebite should always be given IV,

with all facilities ready to hand to treatanaphylaxis in the rare event that it should occur.

2. Intravenous fluids running.

3. Dilute the antivenom about 1:10 (1:5 or less may be

needed if volume is a problem, i.e. polyvalent

antivenom, paediatric patient), in IV fluid (e.g. normal

saline, or Hartmans).

4. Start infusion very slowly carefully observing patient

for reaction (look for flushing, rash, tachycardia,

hypotension, bronchospasm; in children warning

signs also include nasal, palatal, or ocular pruritis,

coughing, sneezing, profuse sweating, faecal or

urinary urgency or incontinence, abdominal pain, and

a sense of impending doom) and increase rate aiming

to give whole dose over 15 to 20 minutes.

5. If the patient has had 25 mLs or more Antivenom then

consider a 7-day course of prophylactic oral steroids.

6. Ensure snakebite patients are followed up adequately,

particularly if given Antivenom, watching specifically

for serum sickness.

3.13.3 Management of an anaphylactic reaction

1. Most reactions are related to the rate of antivenom

infusion.

2. Some mild reactions resolve with temporary cessation

of the antivenom infusion and recommencing

infusion at a slower rate.

3. Envenomed patients may be severely coagulopathic,

so caution must be observed when giving Adrenaline

to avoid blood pressure surges, which might lead to

intracerebral haemorrhage.

4. Initial management of severe reactions (sudden

hypotension, bronchospasm):

a. Suspend the antivenom infusion

b. Lie the patient flat (if not already), continue high

flow/100% oxygen and support airway/ventilation

as required

c. Rapid infusion of 1L Normal Saline (20 mL/kg in

children) over 2–3 minutes

d. Adrenaline IM into the lateral thigh, 0.01mg/kg to

maximum of 0.3 mg (observe puncture site for


bleeding). Alternatively an IV Adrenaline infusion

may be used as per point 5b below

e. Liaise with toxicology service regarding ongoing

management

5. For reactions that do not respond to initial management:

a. If hypotensive, repeat Normal Saline bolus as

above (up to 50mL/kg may be required)

b. Commence IV infusion of adrenaline

(0.5–1mL/kg/hour, of 1mg in 100mL) and titrate

according to response; monitor BP every 3–5

minutes (using the arm opposite to the infusion);

beware that as the reaction resolves adrenaline

requirements will fall, the blood pressure will rise

and the infusion rate will need to be reduced

6. Consider nebulised salbutamol for bronchospasm,

nebulised adrenaline for upper airway obstruction,

and IV atropine for severe bradycardia.

7. Seek advice urgently from the local/regional ED

Consultant and/or ICU Consultant.

3.14 Snakebite coagulopathy

3.14.1 Defibrination

Some snakes may cause a significant coagulopathy as part

of envenoming (e.g. Brown Snakes, Tiger Snakes,

Rough-scaled Snakes, Broad-headed Snakes, Stephen’s

Banded Snakes, Taipans). This is due to potent

procoagulants in the venom, which in vivo cause

consumption of fibrinogen and fibrinolysis i.e.

Defibrination Syndrome.

This may occur rapidly following envenoming, within 30

to 60 minutes, with the blood being unable to clot.

Platelets are usually unaffected.

Snakebite coagulopathy can prove complex to manage,

and it is preferable to treat the patient in a major

hospital, with full coagulation laboratory facilities on site.

Tests for coagulopathy:

1. If there is no laboratory in your hospital, perform a

whole blood clotting time (5 to 10 mL venous blood in

a glass tube, e.g. test tube, and observe time to clot;

normal is less than 10 mins, if there is a coagulopathy

there will be no clotting at 15 minutes or only a very

weak clot). However, performing a WBCT is not a

substitute for laboratory coagulation tests and should

only be used as initial assessment while transfer to a

hospital with laboratory facilities is being organised.

2. Simultaneously take blood for later laboratory tests.

3. The most useful tests are: prothrombin ratio (INR),

aPTT, fibrinogen level, and fibrinogen degradation

products (XDP/d-dimer or FDP).

4. In some laboratories a thrombin clotting time (TCT)

may be useful to assess fibrinogen level.

5. A complete blood picture (CBP/FBE) should be

performed for platelet count.

6. In most cases, a single batch of tests will not be

sufficient, and serial studies will be needed.

Expected results in coagulopathy:

1. Whole blood clotting time will be greater than 15

minutes or there may be only a weak clot in less

severe cases (usually will not clot even after 1 hour) /

(normal = less than 10 minutes).

2. INR (prothrombin time) grossly prolonged (>4, usually

infinity) / (normal = 1.0).

3. aPTT grossly prolonged (>150 secs) / (normal = less

than 40 secs).

4. Thrombin clotting time (TCT) grossly prolonged

(>150 secs) (normal 15 secs).

5. NOTE: TCT may be the first parameter to show

improvement as a result of antivenom therapy,

dropping from >150 secs to less than 100 secs. If this

occurs it probably indicates that enough antivenom

has been given, despite the lack of improvement in

other parameters, therefore cease further antivenom

therapy and repeat tests in 1 hour to confirm trend

of improvement.

6. Fibrinogen level very low (<0.1g/L) / (normal = 1.5 to

4.0g/L). This is the key diagnostic finding in

defibrination coagulopathy.

7. Fibrinogen degradation products grossly elevated

(XDP/d-dimer > 16) / (normal = <0.25). This is

another key diagnostic finding.

8. NOTE: Degradation products are in themselves

anticoagulant, and at such high levels may interfere

with some clotting tests, giving falsely high levels of

abnormality, particularly INR and aPTT on some

automated coagulation machines. This may obscure

the first signs of recovery.

Management principles:

1. If initial studies are normal, remove PIB first aid and

repeat studies after 2 hours, or sooner if the patient

appears envenomed.


2. If the second set of tests are also normal, repeat a

third time, a further 3 hours later.

3. If there is a significant coagulopathy (unclottable blood,

or INR>2 + low fibrinogen), then this must be treated.

4. Antivenom is the treatment of choice. Replacement

therapy with clotting factors (e.g. whole blood, FFP,

cryoprecipitate) should be avoided as it is liable to

make the coagulopathy worse if there is still active

venom. Once active venom is all neutralised by

antivenom normal homeostasis rapidly rectifies the

problem (sometimes within 3 hours), placing the

patient out of danger (i.e. INR <4), usually without

need of any other treatment.

5. Antivenom therapy can be titrated against the

resolution of the coagulopathy, in particular, the

fibrinogen level. After the initial dose of antivenom

retest clotting studies at 3 and 6 hours after

completion of antivenom dose. If still showing a non-

resolving coagulopathy at 6 hours (i.e. no significant

rise in fibrinogen level), it is usually necessary to give

more antivenom and repeat tests as above,

continuing this process until there is evidence of

resolution, but if there is no resolution after an

adequate initial dose, then expert advice should be

sought to determine further dosing, rather than

giving ever increasing amounts of antivenom.

6. NOTE: even if enough antivenom has been given,

many coagulation parameters will remain abnormal

for hours or days, especially fibrinogen degradation

products, which may remain elevated for 48 hours,

longer if there is renal failure. A rise in fibrinogen

level from zero to detectable is the key indicator of

resolution of the defibrination coagulopathy, not a

return to normal fibrinogen levels, which may take

many hours. In some laboratories, the first evidence

of such a rise may be a fall in the aPTT or INR, rather

than a change in detectable fibrinogen titres.

3.14.2 Anticoagulation

This occurs after some severe bites by Mulga Snakes,

Collett’s Snakes and possibly Spotted/Blue-bellied Black

Snakes and is due to direct anticoagulants in the venom,

which interfere with the extrinsic and, to a lesser extent,

the intrinsic clotting pathways.

This can result in a prolonged clotting time, elevated INR

and aPTT, but fibrinogen levels and fibrinogen degradation

products are within the normal range. The INR, in

particular, may be grossly elevated, occasionally >12.

However, without a full clotting laboratory, this may be

hard to ascertain, and the whole blood clotting time

might be prolonged in these patients, though a clot

should eventually form, unlike true defibrination

coagulopathy, as discussed earlier.

Experience has shown that persistent ooze from the bite

site or elsewhere is not likely as a result of venom

induced direct anticoagulation, again, different to

defibrination coagulopathy. Brown Snakes, Tiger Snakes,

Taipans and other species causing defibrination do not

cause this direct anticoagulation, as discussed earlier.

Antivenom is very effective at rapidly reversing direct

anticoagulation coagulopathy. Usually one vial of

antivenom will suffice.

3.14.3 Snakebite myolysis

This occurs most commonly after bites by Tiger Snakes,

Rough-scaled Snakes and Mulga Snakes/King Browns,

but may also occur occasionally after Taipan bites, while

bites by Red-bellied Black Snakes and Spotted/Blue-

bellied Black Snakes may result in low level myolysis

(CK 500–3,000IU).

It is the result of widespread direct damage to striated

muscle cells, resulting in complete muscle cell breakdown

within 1–3 days, though damage probably commences

within 1–3 hours of venom reaching the muscle. Full

recovery is possible, but will take 4+ weeks.

The key diagnostic indicators are myoglobinuria (easily

mistaken for haematuria) and a dramatic rise in plasma CK.

The latter may reach figures much greater than

100,000IU. In addition, patients complain of generalised

muscle pain, with tender muscles.

The secondary effects of myolysis are renal failure and

massive hyperkalaemia, which can be very difficult to

control and has proven lethal.

Once myolysis is established it is uncertain if antivenom

will reverse damage, but in severe cases it may be worth

trying further large doses of specific antivenom.

3.14.4 Snakebite neurotoxic paralysis

Presynaptic neurotoxic flaccid paralysis may occur after

bites by Tiger Snakes, Rough-scaled Snakes,

Copperheads, Taipans, rarely Brown Snakes.

It usually first manifests as ptosis, 1–3+ hours after the

bite, with potential progression to partial ophthalmoplegia,

complete ophthalmoplegia, fixed dilated pupils, dysarthria,

dysphagia, peripheral weakness, culminating in


respiratory paralysis, though it may take 24+ hours to

reach this final stage. Once complete paralysis is

established it may take days, weeks or longer to reverse

sufficiently for the patient to survive off a ventilator.

Antivenom will not reverse well established presynaptic

paralysis.

Pure postsynaptic neurotoxic flaccid paralysis may occur

after bites by Death Adders, resulting in similar, but often

more rapid progression of symptoms and signs. This form

of paralysis is usually reversible if sufficient antivenom is

given. Neostigmine may also reduce the degree of paralysis.

3.14.5 Follow-up of snakebite patients

All patients with systemic envenoming should be

followed up over 6 months, with particular concern for

serum sickness over the first 14 days.

Consider giving a 7-day course of oral steroids as prophylaxis

if more than 25 mLs of antivenom has been given.

It is important to follow up all patients with initially trivial

or no apparent envenoming, especially if discharged less

than 24 hours post-bite, to ensure late onset envenoming

is not missed. In particular, look for late onset neurotoxic

envenoming, myolysis (not if proven Brown Snake bite)

and renal damage.

3.15 Management of the severely illpatient where diagnosis ofsnakebite is obscure

If the patient presents with unexplained onset of

collapse, convulsions, bleeding, paralysis, rhabdomyolysis

(e.g. muscle breakdown, myoglobinuria), or renal failure,

in a setting where snakebite might have occurred (e.g. in

rural areas, or gardens, paddocks, long grass in urban

areas), and particularly in children who may give no

history of exposure to snakes, then include snakebite in

the differential diagnosis.

Useful tests to establish if there has been a snakebite

include:

■ Examine patient on exposed areas for bite marks or

scratches.

■ Whole blood clotting time or coagulation studies to

establish if there is a coagulopathy.

■ Check for myolysis manifested by dark or red urine

indicative of myoglobinuria (positive for “blood” and

so may be mistaken for haematuria), elevated CK

(>1000).

■ Test for venom in urine using SVDK.

■ If in doubt discuss with a Clinical Toxicologist or

Toxicologist at the NSW Poisons InformationCentre on 131126 or your local Critical Care Referral

Network.

3.16 Management of the patient withno evidence of envenomation

3.16.1 Relevant history

■ Was a snake seen to bite (?multiple bites) OR were

the circumstances such that a bite might have

occurred?

■ When did the patient get bitten (elapsed time)?

■ Description of snake if possible (colour, length).

■ Geographic location the incident occurred (snakes in

the area).

■ Timing and type of first aid and activity after the bite.

■ Determine if there has been any evidence of

envenoming; specifically ask about headache,

nausea, 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 the bite site, pain in lymph nodes

draining the bite area (axilla or groin), loss of

consciousness, convulsions.

■ Relevant past history; specifically allergy or past

exposure to antivenom, atopic history, renal, cardiac,

or respiratory disease.

3.16.2 Examination

Assess for:

■ Evidence of a bite (if there is an adequate first aid

bandage in place, cut it away from over the bite site,

keeping bandage away from area adjacent to skin

(DO NOT WASH WOUND; SWAB FOR VENOMDETECTION) looking for evidence of multiple bites,

or venom movement (i.e. swollen or tender draining

lymph nodes).

■ Neurotoxic paralysis (ptosis or drooping eyelids,

diplopia or double vision, dysarthria or slurred

speech, limb weakness, respiratory distress).

■ Coagulopathy (bleeding from bite site or elsewhere).

■ Muscle damage (muscle tenderness, pain on

movement, weakness, urine colour).


3.16.3 Investigations

■ Whole blood clotting time in a glass tube OR

■ Complete blood picture (CBP/FBE/FBC)

■ Coagulation studies (PT/INR, aPTT, Fibrinogen, d-

dimer/XDP/FDP)

■ Electrolytes (especially K++), renal function, CK (for

myolysis)

If envenomation is evident then refer to the relevant

section in these guidelines and the Snakebite

Management Chart (Figure 13: page 20).

If envenomation is not evident then the patient will still

need admission to hospital for observation overnight,

preferably to a high intensity nursing area, ensuring that

nursing staff are instructed to regularly check for signs of

emerging envenomation, in particular early signs of

paralysis (e.g. ptosis, diplopia, etc). (See Appendix 3.)

NOTE: There is no point in leaving first aid in place if the

patient is well and in hospital and the hospital is able to

treat snakebite (i.e. has the appropriate antivenom

available). The first aid bandage and splint merely delays

venom absorption, it does not inactivate venom, and

delay in removing first aid will delay onset of definitive

treatment of snakebite.


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