Snake Spider Guidelines Gl2007 006 3

1. SECTION 3
Snakebite
Key principles Figure (1) Ptosis following Tiger Snake bite
■ 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
Figure (2) Ptosis and partial gaze paralysis following
hours after the bite or after removal of effective first
Death Adder bite
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 Coagulopathy: cause includes defibrination with low
presentation. fibrinogen, unclottable blood but usually normal platelet
count, or direct anticoagulation, with normal fibrinogen
3.1 Snakebite envenomation and platelet count. Both types cause elevated prothrombin
ratio (INR). Signs include: bleeding from bite wound,
Major problems may include one or more of the venepunctures, rarely haematemesis and haematuria.
following effects of the venom (note these are principally
systemic rather than local effects): Figure (3) Oozing Venepuncture Site
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.
PAGE 8 NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines

2. Myolysis: caused by generalised destruction of skeletal ■ Leave PIB in place until patient arrives at a place of
muscle with high serum CK (creatine kinase) and definitive care (hospital with appropriate antivenom etc).
myoglobinuria (red to brown urine testing positive for ■ As soon as possible after applying first aid as above,
blood; can be confused with true haematuria), notify the relevant doctor or hospital, to organise
occasionally severe hyperkalaemia. Signs include: muscle medical evacuation.
movement pain or weakness, and red or brown urine.
■ If the snake was brought with the patient, place it in
Figure (4) Myoglobinuria alcohol (if practical), and ensure it goes with the
patient when evacuation occurs.
Figure (5a) Pressure immobilisation bandaging
Renal damage: primary or secondary (myolysis, Figure (5b) Pressure Immobilisation Bandaging
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:
Figure (5c) Pressure immobilisation bandaging
■ 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
NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines PAGE 9

3. 3.3 Hospital cllinical assessment 3.3.2 Clinical assessment
Assess the patient for the following:
3.3.1 History
■ Evidence of a bite (if an adequate first aid bandage is
1. Establish whether the patient has a in place cut the first aid bandage away from over bite
confirmed/witnessed snake bite (single or multiple) site and the area immediately surrounding the bite)
OR were the circumstances such that a bite might
■ DO NOT WASH THE WOUND – SWAB FOR VENOM
have occurred:
DETECTION using the Snake Venom Detection
2. When the patient was bitten (elapsed time) Kit (SVDK) (refer to the SVDK section at page 11 in
3. Description of snake if possible (colour, length) these guidelines for technique of venom detection).
Examine for evidence of multiple bites, or venom
4. Geographic location that the incident occurred
movement (eg. swollen or tender draining lymph nodes)
(snakes in area)
■ Neurotoxic paralysis (ptosis, ophthalmoplegia, diplopia,
5. Timing and type of first aid, and activity, following
dysarthria, limb weakness, respiratory distress)
the bite
■ Coagulopathy (bleeding gums, prolonged bleeding
6. Type and timing of symptoms, in particular:
from venepuncture sites or other wounds, including
a headache the bite site)
b nausea ■ Muscle damage (muscle tenderness, pain on movement,
c vomiting weakness, dark or red urine indicating myoglobinuria)
d abdominal pain ■ Oliguria, anuria, or myoglobinuria
e blurred or double vision ■ Period of unconsciousness or fitting
f slurring of speech ■ General symptoms such as headache, vomiting,
g muscle weakness abdominal pain, but beware of these in isolation (i.e.
anxiety reaction only). If all other clinical and
h respiratory distress
laboratory indicators are normal, such general
i bleeding from the bite site or elsewhere symptoms alone are not usually sufficient reason to
j passing dark or red urine commence antivenom therapy
k local pain or swelling at the bite site 3.3.3 Systemic envenomation
l pain in lymph nodes draining the bite area (axilla,
If it is evident that Antivenom Therapy will be required
or groin),
then refer to the Antivenom Administration section at
m loss of consciousness and/or convulsions. page 22 in these guidelines).
7. Relevant past history – specifically ask about allergy
Systemic envenomation is present if there is one or more
or past exposure to antivenom, atopic (allergy)
of the following:
history, renal, cardiac, or respiratory disease and
medications (eg. anticoagulants etc).
■ Neurotoxic Paralysis (e.g. ptosis, ophthalmoplegia,
limb weakness, respiratory effects)
3.3.2 Presentation scenarios ■ Significant Coagulopathy (e.g. unclottable blood,
INR>2, prolonged bleeding from wounds and
■ Possible or definite snakebite.
venepunctures)
■ The patient presents unwell, diagnosis uncertain.
■ Significant Myolysis (myoglobinuria)
There is a history of possible exposure to snakes (i.e.
walking in long grass etc), and the patient has any of ■ Unconsciousness or convulsions
the following: loss of consciousness, convulsions, Early non-specific symptoms such as headache, vomiting,
headache, vomiting, weakness or paralysis (initially abdominal pain may indicate developing envenomation.
ptosis, diplopia, slurred speech), dark or red urine, Beware of these as purely manifestations of anxiety
bleeding, renal failure then consider snakebite. rather than envenomation. If these are the only evidence
■ The patient is unwell and may be envenomated. of envenomation then be cautious in deciding if
antivenom is required.
■ The patient is well with no apparent envenomation.
PAGE 10 NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines

4. 3.4 Snake Venom Detection Kit (SVDK) Figure (6) Snake Venom Detection Kits
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 1. The best sample is a swab from the bite site. Take an
supplied SVDK fluid): unused sample diluent bottle (currently yellow top)
and use fingernail to lever off the dropper cap.
– Cut away bandage over bite site and swab for
venom detection 2. Moisten the swab stick provided, in the solution in
the bottle. Rub the swab firmly over the bite site and
– Collect at earliest opportunity after presentation
adjacent skin.
to hospital
Figure (7) Swab bite site and adjacent skin
– 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 3. Place the end of the swab back in the bottle
■ Administer antivenom if there is clinical and/or containing solution and twirl around for a few
laboratory evidence of significant systemic moments to transfer venom into solution. Then
envenoming indicated by the clinical signs and proceed to use the kit as indicated in the instructions.
symptoms listed 4. A positive result is indicated by a colour change (to
■ NB: Positive venom detection from the bite site does blue) in one of the first five wells, plus the positive
not imply systemic envenoming and is not in itself an control well (well 7), within 10 minutes in the last
indication for antivenom stage of the test. Observe all tubes carefully
throughout this last 10 minute period to identify the
■ A negative result does not exclude either a snakebite
first well to change colour. If one tube changes
or systemic envenoming
colour, all will do so eventually, but only the first tube
■ Always confirm the SVDK result by comparing with to change is relevant.
result from diagnostic algorithms as outlined in Figure
(12) combined with knowledge of snakes in region Figure (8) Positive venom detection
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.
NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines PAGE 11

5. 5. A positive result usually indicates that: 11. The SVDK should not be used to determine if a
■ venom was present on the skin snakebite is a likely diagnosis. The only purpose of
the SVDK is to determine best choice of
■ the type of snake involved
antivenom, should antivenom be indicated on
■ the appropriate monovalent antivenom to use should clinical or laboratory grounds.
this be needed
Figure (9) Snake/well correlation
6. A positive SVDK result does not indicate systemic
envenomation and is not an indicator for antivenom
therapy. Well 1 Tiger Snake Venom
7. A negative SVDK result does not exclude snakebite
(see these Guidelines on each type of snake for
Well 2 Brown Snake Venom
further guidance on interpretation).
8. Be aware that false positives from bite site swabs,
though rare, are possible. Well 3 Mulga Snake Venom
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 Well 4 Death Adder Venom
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 Well 5 Taipan Venom
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 Well 6 Negative Control
result for brown snake venom, in the absence of
clinical or laboratory evidence of envenoming, such
as coagulopathy, in nearly all cases should be Well 7 Positive Control
considered a false positive and therefore of no
diagnostic value.
Well 8 Blank Well
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.
Figure (10) Actual SVDK result in a case of Mulga Snake bite — CSL Snake venom detection kit
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)
PAGE 12 NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines

6. Figure (11) Common patterns of SVDK venom detection results
Well number: Diagnostic pattern:
1 2 3 4 5 6 7 8
Only well 7 positive: No snake venom detected.
This result does not include snakebite.
Wells 7 and 1 positive: If systemic effects include
defibrination, paralysis ± myolysis, suggests Tiger Snake or
Rough-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 defibrination
coagulopathy, ± renal damage. Paralysis is unlikely and
myolysis should not occur.
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.
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 seen
with bites by several species. With a Copperhead bite, if
there is systemic envenoming, expect paralysis without
coagulopathy. 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.
NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines PAGE 13

7. 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 significant Obvious redness, swelling,
redness, swelling, bruising ± bruising
Moderate to severe Minimal or no Marked swelling after Only mild swelling
local pain local pain 3+ hours after 3+ hours
• Brown Snake • Mulga Snake • Tiger Snake
• ? Death Adder • Red-bellied Black Snake • Rough-scaled Snake
• ? Taipan
• Yellow-faced Whip Snake • ? Taipan
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.
Systemic effects of bite
Is there a coagulopathy?
Yes No Is there paralysis?
Defibrination Anti-coagulation Yes No
coagulopathy normal
low fibrinogen fibrinogen Is there major Is there major
raised FDP/XDP and FDP/XDP myolysis? myolysis?
Is there paralysis Is there
± myolisis? paralysis? No Yes No
Yes No No Yes
• Brown Snake • Mulga Snake • Mulga Snake • Red-bellied
• Tiger snake • ? Death
• Broad-headed • Spotted • Spotted Black Black Snake
• Rough-scaled Adder
Snake or Black Snake Snake • Yellow-Faced
snake • ? Copper-
Stephen’s • Collett’s • Collett’s Snake Whip Snake
• ? Taipan head
Banded Snake Snake • Small-eyed Snake
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
PAGE 14 NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines

8. 3.5 Laboratory evidence of 2. Defibrination coagulopathy + paralysis ± mild
envenomation myolysis
Bite site is variable and there may be an ooze of blood.
Laboratory testing in cases of possible snakebite is crucial
Likely snakes include:
in diagnosis and is urgent. Any delay in delivering results
may delay definitive and life saving treatment. Frequent ■ Taipan and Inland Taipan (Genus Oxyuranus).
repeat testing is almost always required. This is to ensure
3. Defibrination coagulopathy + paralysis +
that delayed envenoming or failure to respond to initial
moderate to severe myolysis
treatment is not missed.
Bite site is usually painful with mild swelling, bruising,
3.5.1 Laboratory testing redness, and there may also be an ooze of blood. Likely
snakes include:
■ Laboratory tests to monitor for envenoming should
include coagulation studies (INR, aPTT, fibrinogen, ■ Tiger Snakes (Genus Notechis)
d-dimer), FBC/CBP (including blood film examination ■ Rough-Scaled Snake (Genus Tropidechis)
for schistocytes), EUC and CK. (Where direct
fibrinogen testing is possible, down to very low levels 4. Moderate to marked myolysis + anticoagulant
of fibrinogen, this is also a useful test). coagulopathy (fibrinogen normal, no raised
FDP/XDP)
■ If initial tests are normal, repeat testing at least twice,
at approximately 2–3 hour intervals, or more urgently No paralysis (beware major myolysis mimicking paralysis).
if the patient develops clinical evidence suggestive of Bite site is usually painful, often with marked swelling
envenoming. and sometimes bruising. Persistent blood ooze is not
common. Likely snakes include:
■ Where laboratory testing is not rapidly accessible a
whole blood clotting time (WBCT) may be performed ■ Mulga snake, Collett’s snake, Spotted black snake
but should not delay arrangements for transfer of the (Genus Pseudechis).
patient. (WBCT – put 10 ml venous blood into a glass
5. Moderate to marked myolysis
test tube and measure time taken to clot – normal
less than 10 mins). No paralysis (beware major myolysis mimicking paralysis)
or coagulopathy. Bite site is usually painful, has marked
■ An INR>2 indicates a coagulopathy (unless the
swelling and sometimes bruising. Persistent blood ooze
patient is on Warfarin).
not common. Likely snakes include:
■ Myoglobinuria or a significantly raised CK indicates
■ Mulga snake, Collett’s Snake, Spotted Black Snake
myolysis.
(Genus Pseudechis).
■ Abnormally raised creatinine or urea indicates renal
■ Eastern Small-Eyed Snake (Rhinoplocephalus
damage.
nigrescens).
■ Cut away the bandage over bite site and swab for
venom detection (CSL Snake Venom Detection Kit). 6. Paralysis (postsynaptic: reverses with antivenom
therapy) ± mild anticoagulant coagulopathy
■ The best sample for venom detection is a bite site swab.
No myolysis and renal damage unlikely. Bite site is often
3.5.2 Clinical and laboratory profiles painful, but with little swelling, redness or bruising.
following Australian snakebite Persistent blood ooze unlikely. Likely snakes include:
1. Defibrination coagulopathy ■ Death Adders (Genus Acanthophis).
No paralysis or myolysis. The bite site usually has minimal 7. General symptoms of envenomation (some or all
or no pain, no significant swelling, bruising or redness, of: headache, nausea, vomiting, diarrhoea,
but there may be ooze of blood. Likely snakes include: abdominal pain, dizziness, collapse).
■ Brown Snakes (all species except Ringed Brown No paralysis or coagulopathy with no, or generally mild,
Snake) (Genus Pseudonaja) myolysis. Bite site is usually painful with marked swelling
■ Broad-headed Snakes, including Stephen’s Banded and sometimes bruising. Persistent blood ooze not
Snake and Pale-headed Snake (Genus Hoplocephalus) common.
NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines PAGE 15

9. Likely snakes include: ■ This is an important indication of possible
developing coagulopathy. However, a similar
■ Red-bellied Black Snake (Pseudechis porphyriacus)
picture is present in a patient with venous
and mild bites by Spotted Black snake and Collett’s
thrombosis problems, so careful clinical judgement
Snake (Genus Pseudechis).
will be required by the treating doctor, to decide
■ Yellow-faced Whip Snake and other large Whip which is the more likely diagnostic explanation.
Snakes (Genus Demansia).
b. Anticoagulation-type coagulopathy (Mulga
Snakes, Collett’s Snake).
3.6 Essential information for hospital ■ Characterised by mild to grossly prolonged PT and
laboratory staff aPTT, but normal fibrinogen levels and no significant
Details of venom actions and venom profiles for each elevation of d-dimer/FDP.
major snake species are contained in these guidelines and c. Patients on Warfarin and similar anticoagulants
should be referred to when interpreting laboratory results.
■ These patients may present a problem in interpreting
results, if bitten by a snake. Warfarin should cause
3.6.1 Required laboratory testing
prolongation of PT in particular, sometimes with
1. Coagulation Studies: PT/INR, aPTT, fibrinogen level, elevated d-dimer/FDP, but normal fibrinogen. If
d-dimer/FDP, platelet count (Where direct fibrinogen snakebite defibrination coagulopathy is overlaid
testing is possible, down to very low levels of on this background, in most cases, fibrinogen will
fibrinogen, this is also a useful test). be depleted and d-dimer/FDP grossly elevated, with
a. Defibrination-type coagulopathy (BrownSnakes, an INR of >4, usually >10 (actually infinity). This
Tiger Snakes, Rough-scaled Snake, Taipans, Broad- should not cause confusion in interpretation, as
headed Snake group). such a pattern is clearly not due to Warfarin, but a
result of envenoming.
■ Characterised by grossly prolonged PT & aPTT,
undetectable fibrinogen, grossly elevated d-dimer/ ■ This pattern may be complicated by the fact that
FDP, platelets normal (sometimes slightly low). warfarin causes low levels of factors, which the
toxins need to act on, leading to different
■ Some coagulation machines will have trouble
pharmacodynamics.
giving results in this situation. If the machine
indicates gross prolongation of PT/aPTT, but ■ In cases with early or mild snakebite defibrination
fibrinogen “very high”, this usually indicates coagulopathy, changes may be subtle. In this
undetectable fibrinogen. setting, significant elevation of d-dimer/FDP may be
the most important diagnostic clue that envenoming
■ If d-dimer/FDP is elevated, you can be sure
is occurring. In cases of snakebite anticoagulation-
fibrinogen will be very low, not very high. As soon
type coagulopathy, interpretation may be more
as such a picture is evident, immediately report
difficult, as elevation of d-dimer/FDP is not a feature.
this to the treating doctor.
In this setting coagulation tests may not give clear
■ Do not delay while trying to get final results from cut evidence of envenoming. Fortunately, in these
the machine. Similarly, if d-dimer/FDP is elevated, cases, clinical features and rising CK are likely to
report this first, then go back and determine the assist in diagnosis of envenoming.
actual level, which may take time.
2. Complete blood picture (Platelets, Hb, WCC,
■ Do not waste valuable time retesting and calling absolute lymphocyte count, including blood film
for new specimens because the machine cannot examination for schistocytes).
cope with the grossly abnormal results. Snakebite
a. Acute systemic envenoming usually causes an
coagulopathy is common and time is of the
elevated WCC
essence. So, look for the typical defibrination
picture and report this as soon as it is clear that it b. There may be an associated absolute lymphopenia,
is present. Be aware that in mild cases, in the which can be quite marked
early stages, PT/INR and aPTT may be normal, c. Lymphopenia is always present in tiger snake bites
fibrinogen level normal or only slightly decreased, with systemic envenoming, but is less consistent for
but d-dimer/FDP will be elevated. other snake species
PAGE 16 NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines

10. d. Thrombocytopenia is not a common acute feature of b. There is no defined picture of envenoming-induced
envenoming and when present, is often associated liver damage in humans. However, LDH is a useful
with renal damage test in patients with haemolysis, either in Brown
e. In rare cases, especially with Brown Snake bite, a Snake bites that develop microangiopathic haemolytic
thrombocytopenia like picture may develop, often anaemia or in Black Snake where direct toxin
after the initial defibrination coagulopathy is mediated haemolysis may occur.
responding to antivenom. In such cases there will be
3.2.1 Derived fibrinogen (important
a falling Hb, falling platelet counts, rising creatinine
considerations)
and urea, and usually schistocytes on the blood film.
Derived fibrinogen is merely a reflection of the PT and as
3. Muscle Function (CK) such adds nothing more than a pseudo PT and is not as
a. A number of snakes can cause moderate to severe sensitive as a direct Fibrinogen (Clauss). This is poorly
systemic muscle destruction (myolysis) including recognised with many laboratories not clearly
Mulga Snakes, Collett’s Snake, Tiger Snakes, Rough- distinguishing derived vs direct (Clauss), while others
scaled Snake, Taipans and Black Snakes). report both derived and Clauss.
b. This may take several hours to become evident, Furthermore, there is a limit of quantification/reporting
occasionally days. for Clauss fibrinogen, because this differs on machines
c. Clinically the patient develops muscle pain, weakness and most importantly in the way they are reported or
and myoglobinuria. At a lab level, CK can become understood by the laboratory staff.
grossly elevated.
Some analysers will only allow results such as <0.65, and
d. Significant myolysis is associated with CK levels it is impossible to get anything lower. This is not very
>1,000 IU/L and can exceed 100,000 IU/L (sometimes sensitive because by the time the Fibrinogen is above
far higher than this). In such cases beware associated 0.65 the PT/aPPT have usually started to recover.
hyperkalaemia that can cause lethal cardiac toxicity.
In some laboratories the limit of quantification is <0.5,
e. Measurement of serum or urine myoglobin levels does
however they will often report 0.2 or 0.3 but say it is
not add to the diagnosis, is expensive, and treating
below the limit of quantification (not detection) so they
doctors should be encouraged to use CK levels as the
can’t guarantee the difference.
indicator of myolysis rather than myoglobin levels.
This is an important difference in those reports below
4. Renal function (creatinine and urea)
the LOQ and the LOD, which may not be clear to some
Snakebite can cause renal damage and occasionally renal laboratories.
failure, often secondary to coagulopathy, myolysis, or
hypotension. In mild cases, especially with brown The issues around low levels of Fibrinogen are complex,
snakebite, there may be a slow rise in creatinine and not necessarily well understood and are often limited by
urea over the first few days, without polyuric or anuric the analyser only reporting <LOQ. This is primarily due to
renal failure, which will reverse and gradually improve the broad acceptance that a Fibrinogen <1.5 is low and
over a week or so. However, rising creatinine and urea often associated with significant haematological
should always be flagged, as it may indicate progression abnormality. However, treated snake bite patients have
to major renal failure. very low Fibrinogens which are actually recovering, but
take time to get >1.5. For these patients it is important
5. Electrolytes to know that the Fibrinogen is just detectable.
Hyperkalaemia is the major risk, most often in It is also common to find a “near normal” PT/aPTT when
association with myolysis and secondary renal failure. there is still a low Fibrinogen around 0.5 – 0.9. This is a
However, hyponatraemia can also develop, most likely in problem for the analyser and may not be understood
response to over vigorous IV fluid replacement. well by Haematologists who are not familiar with results
demonstrating a slightly raised INR and a low Fibrinogen.
6. Liver function tests
a. LFTs are not routine tests in snakebite cases. It is suspected, but not yet proven, that in snake bite the
Temporary elevation of LFTs sometimes occurs but is PT is driven by factor V deficiency (and also factor VIII),
rarely of clinical significance and not so much by fibrinogen – the former recovers
more rapidly, which is manifested by a normalisation of
NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines PAGE 17

11. the PT and a gradual recovery of fibrinogen. This is likely results assessed, venom detection performed and
to be the main driver for the use of Fresh Frozen Plasma result obtained), stabilised (ABC, IV line in situ, IV
(FFP) in these situations. fluid load) and if envenomed, treatment commenced
(appropriate type and dose of IV antivenom given).
Given the complexity of interpreting derived Fibrinogen
and very low Fibrinogen levels in these patients, it is – In a significant number of patients, initial clinical
strongly recommended that early expert advice be and laboratory examination will be normal, with
obtained in the first instance through the Poisons no indication of systemic envenoming. Such
Information Centre on phone 131126. patients do not require antivenom at this time
and the pressure immobilisation bandage first aid
should be removed.
3.7 Hospital clinical management – The patient should then be fully re-evaluated
Venomous snakebite is a medical emergency, potentially within 2 hours (including repeat laboratory
life threatening, and is not a simple matter of just giving testing) or earlier if symptoms develop.
antivenom. Expert advice is available from the Poisons – Do not leave pressure immobilisation bandage in
Information Centre on phone 131126 and through place for long periods of time, especially in an
the local Critical Care Referral Network. asymptomatic patient.
A considerable number of snakebites do not result in
significant illness, and do not require antivenom, but all 3.8 Clinical management of definite
probable snakebites should be admitted for observation or probable snakebite in a hospital
for at least 12+ hrs or overnight, as some serious effects
without antivenom available
may be delayed.
Where the patient presents with a definite or possible
Following the immediate clinical management, the snakebite.
definitive clinical management will be dependant upon
whether or not the health facility has antivenom stocks 1. If not already applied, immediately apply correct first
immediately available. aid, namely a broad compressive bandage bound first
over the bite site, at the same pressure as for a sprain
3.7.1 Immediate clinical management (i.e. not so tight that it occludes the blood supply),
then bind the bandage over as much of the bitten
■ Assess and maintain airway
limb as possible, going over the top of clothing, and
■ 100% Oxygen keeping the limb as still as possible.
■ Respiratory support as indicated 2. Once the limb is bandaged then immobilise it using a
■ Establish intravenous access and administer splint and keep it in a neutral position (not elevated
intravenous fluids (fluid load) or below the patient).
■ Commence serial clinical observations and serial 3. Do not wash the wound, but if a venom detection kit
laboratory testing. If clinical (including antivenom is available then swab the wound prior to applying
stocks) or laboratory facilities are inadequate, first aid, but do not delay first aid significantly just to
maintain pressure immobilisation bandage and swab for venom, unless the patient appears well and
arrange retrieval to an appropriate hospital greater than 20 minutes has elapsed since the bite.
■ Antivenom therapy is indicated in most cases if there 4. Keep the patient as still and quiet as possible.
is any evidence of systemic envenoming detected by 5. Fast the patient, and be prepared for vomiting.
clinical observation or on laboratory testing
6. Carefully watch for evidence of envenoming, and if
■ Consult early with the local Critical Care Referral Network, there is respiratory distress then provide respiratory
Clinical Toxicologist and the Poisons Information support.
Centre preferably before commencing antivenom
7. Monitor urine output and colour.
■ Removal of pressure immobilisation bandage:
8. If the snake was brought with the patient, place it in
– The bandage should not be removed until the alcohol (if practical) and ensure it goes with the
patient is fully assessed (clinical history, patient when evacuation occurs.
examination, laboratory tests performed and
PAGE 18 NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines

12. 9. As soon as possible after applying first aid as above If patient already has severe envenomation then apply
and notify the relevant doctor or hospital to organise pressure bandage/ immobilisation first aid if not in situ
medical evacuation. It will assist the retrieval team if (remove only when initial antivenom therapy is completed).
you can give the following patient status report:
■ Name, sex, age of patient 3.9.3 Blood samples
■ Brief history of the suspected bite 1. Whole blood clotting time (in glass test tube)
■ Was a snake seen? 2. Coagulation studies (PT/INR, aPTT, Fibrinogen, XDP/d-
dimerFDP) full blood profile (CBP/FBE including blood
■ What type of snake?
film examination for schistocytes) (Where direct
■ Was it a multiple bite? fibrinogen testing is possible, down to very low levels
■ Are there any symptoms or signs of envenomation? of fibrinogen, this is also a useful test)
(Namely: headache, nausea, vomiting, abdominal 3. Electrolytes, renal function, CK
pain, collapse, convulsions, early paralysis such as
4. Avoid venepuncture in sites where bleeding may be
drooping upper eyelids, double vision, slurred
difficult to control (i.e. femoral, neck, subclavian)
speech, limb weakness, evidence of bleeding
problem such as persistent ooze from the bite
3.9.4 Anaphylaxis
site, evidence of muscle damage such as dark or
red urine, muscle pain). Anaphylaxis due to allergy to venom is occasionally seen:
(i.e. in reptile keepers). Treat with IV Adrenaline infusion or
■ Patient’s past history, particularly past snakebites
IM Adrenaline (initial dose 0.25–0.5 mg.). For suggested
with antivenom therapy, allergic disease, renal or
paediatric dosages and further information, refer to the
heart disease, or use of anticoagulant drugs
relevant section in these guidelines.)
(e.g. warfarin) or anti-platelet drugs (e.g. aspirin
or NSAIDS).
3.9.5 Ongoing care
1. Observe closely for evidence of developing paralysis
3.9 Clinical management of definite
(ptosis and diplopia).
or probable snakebite in a
hospital with antivenom available 2. Monitor urine output – indwelling catheter as
necessary.
3.9.1 Respiratory failure 3. Serial respiratory function (FVC, O2 saturation and/or
Artificial ventilation – mouth to mask; bag/mask, expired CO2).
bag/endotracheal tube as indicated. 4. Check and update Tetanus immunisation status (once
coagulopathy has resolved).
3.9.2 Circulatory failure 5. Avoid unnecessary venepunctures.
1. If cardiac arrest – commence cardiopulmonary 6. Once the patient is stabilised the pressure.
resuscitation. immobilisation bandage may be removed however, if
2. Insert an IV line (normal saline, give initial IV fluid load, the patient has a severe envenomation and requires
500 – 1000ml over 2hrs in adults, 20ml/kg for children, transfer to another hospital and/or if there will be a
then run at maintenance, keep the patient fasted). delay in obtaining further supplies of antivenom,
consider leaving the pressure immobilisation bandage
3. If possible insert long line in cubital fossa or similar,
in situ.
to allow frequent blood sampling and avoid the need
for further venepunctures. 7. If left in situ, then regular limb circulation
observations should be performed.
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.
NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines PAGE 19

13. Figure (13) Snakebite management chart
Patient presents with possible snakebite
Patient is severely envenomed, i.e. has Patient is symptom-free, or has only mild
one or more of: collapse/unconscious, or general symptoms, i.e. has one or more of:
paralytic signs, coagulopathy, myolosis headache, nausea/vomiting, abdominal pain
FIRST AID FIRST AID FIRST AID FIRST AID
Patient has had correct No effective first aid Patient has had correct No effective first aid has been
first aid applied has been applied first aid applied applied DO NOT APPLY
i.e. PIB APPLY PIB first aid i.e. PIB now if >1hr post-bite
Leave PIB in place until patient is stabilised, TREATMENT
fully assessed, and antivenom given (if required)
• Insert IV line, given IV fluid load.
• Take blood for lab tests. *
• Cut away first aid bandage (if present) over bite site and
TREATMENT
swab bite site for venom detection. **
• Attend to ‘ABC’ but be careful of causing bleeding. • Collect urine and check for haemoglobin/myoglobin
• Insert IV line, given IV fluid load. (dip stick) and keep for for venom detection.
• Take blood for lab tests* and swab bite site for venom • Secure supply of antivenom (use Polyvalent AV or a
detection** collect urine and check for haemoglobin/myoglobin mixture of monovalent AVs if snake identity uncertain
(dip stick) and keep bite site swab for venom detection • Monitor fluid balance, consider catheterising if in doubt
• Commence IV antivenom (use Polyvalent or mixture of about urine output.
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
Develops or has significant Remains symptom-free or
• Monitor fluid balance, catheterise if in doubt about
symptoms or signs or minor general symptoms only
urine output.
abnormal blood tests, i.e. (i.e. headache, nausea etc)
paralytic signs, coagulopathy, and blood tests are normal;
myolysis, renal impairment do not give antivenom
Repeat blood tests at 3 hrs and 6 hrs post AV
TREATMENT: Give appropriate Remove first aid once IV line
Coagulopathy is resolving Coagulopathy not resolving Antivenom IV, diluted, inserted, venom detection*
(rise in fibrinogen/reduction (no rise in fibrinogen/ adrenaline ready (in case of and blood tests performed
in whole blood grossly prolonged whole anaphylactoid reaction and reported as normal
clotting time) blood clotting time
Leave PIB first aid in place TREATMENT:
TREATMENT: Continue to TREATMENT: Give more until patient is stabilised Check patient for signs of
monitor closely; repeat antivenom IV, diluted, and antivenom given envenoming frequently and
blood tests to ensure adrenaline ready (in case of
repeat blood tests after
continuing improvement anaphylacticoid reaction
about 2 hrs, then 2–3 hrs later
TREATMENT: Once TREATMENT:
recovered, send home but Admit overnight. If remains
Remains symptom-free or minor general
follow up for serum sick- well, repeat blood tests symptoms only (i.e. headache, nausea etc) and
ness. Consider prophylactic next morning and if blood tests are normal; do not give antivenom
oral steroids for 1 week. normal, send home.
Patient discharged home *Laboratory tests
Coagulation
If no lab quickly available:
• Whole blood clotting time (QBCT) (5–10 ml venous
FIRST AID FOR SNAKE BITE SVDK SNAKE VENOM DETECTION KIT
blood in glass test tube. Measure time to clot; >10 mins
PIB = Broad bandage over **Cut away first aid bandage over bite site only, to allow
suggests coagulopathy but test staff member’s blood
bite site, then rest of bitten limb, visual access and swab for venom detection. NOTE: bite
as normal control.
including toes/fingers, at same site swab is best sample. Only test urine if no bite site
If lab available, request:
pressure as for ankle sprain, available AND patient has systemic envenoming. DO NOT
• Prothrombin time/ INR • aPTT
then splint limb, keep immobile. use SVDK to determine if patient has snakebite.
• FDP/XDP (d-dimer)
• CBP/FBE (platelet count and blood film for schistocytes)
Please note: This chart cannot cover all possible situations and assumes an understanding of the Other
symptoms and signs of local, general and specific envenoming by Australian snakes (see Section • Creatinine and urea • Electrolytes (especially K+)
4: Snakebite, and preceding pages). If in doubt, seek advice from the Poisons Information • CK for myolysis
Centre (131126) and from your local Critical Care Referral Network. © 1998 Dr Julian White • CBP/FBE (WCC for leukocytosis ± lymphopenia
PAGE 20 NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines

14. 3.11 Antivenom therapy your area. In general terms, in eastern NSW, a mixture of
CSL Tiger Snake Antivenom and CSL Brown Snake Anti-
Antivenom is the definitive treatment of envenomation,
venom will often be appropriate, providing a bite from a
potentially life saving and is produced using refined
Death Adder can be excluded on grounds of description
horse serum therefore it is potentially allergenic and as
of the snake. However, there are areas where such a mix
such its use is not without risk. Therefore, antivenom
will not be sufficient, such as far North-Eastern NSW
should only be used if there is systemic envenoming.
where there is a chance of Taipans being present.
Overall, less than 1 in 4 patients require antivenom therapy.
3.11.1 Key antivenom therapy principles 3.12 Antivenom therapy dose
■ The treatment of choice for systemic envenoming is The minimum dose is one vial of the appropriate
to use a monovalent (specific) antivenom in antivenom however for some antivenoms the initial dose
preference to polyvalent antivenom if the identity of is higher.
snake is known.
Multiple bites or severe envenoming mandate higher
■ Use the SVDK in conjunction with the diagnostic doses; increase the dose by 1 to 3 vials, depending on the
algorithms along with consideration of the type of type of antivenom, and be prepared to give more. Four
snakes found in region to determine the most to 6 or more vials is not unusual in a severe snakebite.
appropriate antivenom therapy.
If there is a coagulopathy then the dose can be titrated
■ Consult with the NSW Poisons Information Centre
against serial coagulation results (see relevant section in
Ph: 131126 if unsure or if there is a conflict between
these or guidelines for managing coagulopathy).
the SVDK and diagnostic algorithm results.
■ Do not overlook polyvalent antivenom as backup if
3.12.1 Brown Snake
insufficient monovalent antivenom available.
The starting dose for severe Brown Snake envenomation
■ 1 vial of CSL Polyvalent Snake antivenom is
is currently being investigated by a national multi-centre
equivalent to 1 vial of relevant monovalent
prospective trial. The initial dose may range from 2 to 5
antivenom.
vials.
■ Dosage varies with the type of antivenom, type of
snake and number of bites however, children In small remote centres, the current recommended initial
require the same dose as adults. dose in a life-threatening situation is 2 vials. Organise
medical retrieval as early as possible for the patient to be
■ Further doses of antivenom may be required in major
immediately transferred to the closest Rural Referral
cases.
Hospital for ongoing management and additional doses
as required.
3.11.2 Snake identified
In Rural Referral and Tertiary Referral Hospitals sufficient
Monovalent Antivenom is preferred to Polyvalent as it is
antivenom stocks will be available to give additional doses
less hazardous and has fewer side effects, and is less
as required and replenish stocks at the small remote centres.
expensive. Refer to the relevant section on specific snake
management, in these guidelines, for the appropriate, safe As dosing recommendation may evolve with time,
and effective administration of antivenom therapy. It must consultation with a clinical toxicologist via the New
be noted that bites by some snakes may not need anti- South Wales Poisons Information Centre Phone
venom even if there is mild to moderate envenoming. 131126 is recommended in all cases.
3.11.3 Snake not identified 3.12.2 Tiger Snake
Where an SVDK is not available, or failed, or the patient Starting dose for a major bite is 4 vials of CSL Tiger
requires antivenom before a SVDK result is possible, then Snake Antivenom.
either Polyvalent Antivenom or an appropriate mixture of
Monovalent Antivenoms should be used. Diagnostic For some smaller rural hospitals, the recommended stock
algorithms (Figure 12, page 14) may assist in choice of level is only 2 vials, to be given in life-threatening
antivenom. Refer to Appendix (1) to determine if there is situations, whilst supplementation of stocks from another
an appropriate mix of two monovalent antivenoms for hospital, plus medical retrieval, are being arranged.
NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines PAGE 21

15. 3.12.3 Taipan Snake 7. Record blood pressures on the other side to the
fluid/adrenaline infusion, to avoid prolonged cuff
Starting dose for a major bite is 3 vials of CSL Polyvalent
inflations and thus extravasation of infusion fluids.
or 3 vials of Taipan Antivenom.
3.13.2 Administration method
3.12.4 Mulga Snake
1. Antivenom for snakebite should always be given IV,
Starting dose for a major bite is 1 vial of CSL Black Snake
with all facilities ready to hand to treat
Antivenom or 1 vial Polyvalent Antivenom.
anaphylaxis in the rare event that it should occur.
3.12.5 Red-bellied Black Snake 2. Intravenous fluids running.
3. Dilute the antivenom about 1:10 (1:5 or less may be
Starting dose for a major bite is 1 vial of CSL Tiger Snake
needed if volume is a problem, i.e. polyvalent
Antivenom (not Black Snake Antivenom).
antivenom, paediatric patient), in IV fluid (e.g. normal
saline, or Hartmans).
3.12.6 Death Adder
4. Start infusion very slowly carefully observing patient
Starting dose for a major bite is 1 vial of CSL Polyvalent
for reaction (look for flushing, rash, tachycardia,
or 1 vial Death Adder Antivenom.
hypotension, bronchospasm; in children warning
As dosing recommendation may evolve with time, signs also include nasal, palatal, or ocular pruritis,
consultation with a clinical toxicologist via the New coughing, sneezing, profuse sweating, faecal or
South Wales Poisons Information Centre, phone urinary urgency or incontinence, abdominal pain, and
131126 is recommended in all cases. 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
3.13 Antivenom administration consider a 7-day course of prophylactic oral steroids.
Prepare the patient and clinical environment for potential 6. Ensure snakebite patients are followed up adequately,
anaphylaxis or anaphylactoid reaction to antivenom. particularly if given Antivenom, watching specifically
for serum sickness.
3.13.1 Preparation prior to commencing
antivenom 3.13.3 Management of an anaphylactic reaction
1. High flow oxygen. 1. Most reactions are related to the rate of antivenom
2. Dedicate one small bore (18–20g in adults) IV line to infusion.
antivenom administration, and one large bore IV line 2. Some mild reactions resolve with temporary cessation
(16–14g in adults) for emergency resuscitation of the antivenom infusion and recommencing
(equivalent size suitable for children). infusion at a slower rate.
3. Prepare 1L Normal Saline (20 mL/kg in children) ready 3. Envenomed patients may be severely coagulopathic,
to give under pressure. so caution must be observed when giving Adrenaline
4. Prepare adrenaline 1:1000 (1 mg in 1mL) drawn up to to avoid blood pressure surges, which might lead to
a dose of 0.01 mg/kg (max. 0.3 mg, i.e. max 0.3 mL) intracerebral haemorrhage.
and label “Adrenaline for IM injection only (dose in mg)”. 4. Initial management of severe reactions (sudden
5. Prepare an IV infusion of adrenaline 1 mg in 100mL hypotension, bronchospasm):
or as per local protocol (controlled by infusion pump a. Suspend the antivenom infusion
or syringe driver) ready to attach by a side arm to the
b. Lie the patient flat (if not already), continue high
resuscitation line. Anti-reflux valves must be attached
flow/100% oxygen and support airway/ventilation
above the side arm on any other infusions using this
as required
IV, to prevent adrenaline going back up into the other
fluid bags. To prevent erroneous administration, do c. Rapid infusion of 1L Normal Saline (20 mL/kg in
not attach the adrenaline infusion unless it is needed. children) over 2–3 minutes
6. Continuous monitoring of vital signs including ECG, d. Adrenaline IM into the lateral thigh, 0.01mg/kg to
Pulse, BP and Sa02%. maximum of 0.3 mg (observe puncture site for
PAGE 22 NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines

16. bleeding). Alternatively an IV Adrenaline infusion 2. Simultaneously take blood for later laboratory tests.
may be used as per point 5b below 3. The most useful tests are: prothrombin ratio (INR),
e. Liaise with toxicology service regarding ongoing aPTT, fibrinogen level, and fibrinogen degradation
management products (XDP/d-dimer or FDP).
5. For reactions that do not respond to initial management: 4. In some laboratories a thrombin clotting time (TCT)
a. If hypotensive, repeat Normal Saline bolus as may be useful to assess fibrinogen level.
above (up to 50mL/kg may be required) 5. A complete blood picture (CBP/FBE) should be
b. Commence IV infusion of adrenaline performed for platelet count.
(0.5–1mL/kg/hour, of 1mg in 100mL) and titrate 6. In most cases, a single batch of tests will not be
according to response; monitor BP every 3–5 sufficient, and serial studies will be needed.
minutes (using the arm opposite to the infusion);
beware that as the reaction resolves adrenaline Expected results in coagulopathy:
requirements will fall, the blood pressure will rise 1. Whole blood clotting time will be greater than 15
and the infusion rate will need to be reduced minutes or there may be only a weak clot in less
6. Consider nebulised salbutamol for bronchospasm, severe cases (usually will not clot even after 1 hour) /
nebulised adrenaline for upper airway obstruction, (normal = less than 10 minutes).
and IV atropine for severe bradycardia. 2. INR (prothrombin time) grossly prolonged (>4, usually
7. Seek advice urgently from the local/regional ED infinity) / (normal = 1.0).
Consultant and/or ICU Consultant. 3. aPTT grossly prolonged (>150 secs) / (normal = less
than 40 secs).
3.14 Snakebite coagulopathy 4. Thrombin clotting time (TCT) grossly prolonged
(>150 secs) (normal 15 secs).
3.14.1 Defibrination 5. NOTE: TCT may be the first parameter to show
Some snakes may cause a significant coagulopathy as part improvement as a result of antivenom therapy,
of envenoming (e.g. Brown Snakes, Tiger Snakes, dropping from >150 secs to less than 100 secs. If this
Rough-scaled Snakes, Broad-headed Snakes, Stephen’s occurs it probably indicates that enough antivenom
Banded Snakes, Taipans). This is due to potent has been given, despite the lack of improvement in
procoagulants in the venom, which in vivo cause other parameters, therefore cease further antivenom
consumption of fibrinogen and fibrinolysis i.e. therapy and repeat tests in 1 hour to confirm trend
Defibrination Syndrome. of improvement.
6. Fibrinogen level very low (<0.1g/L) / (normal = 1.5 to
This may occur rapidly following envenoming, within 30
4.0g/L). This is the key diagnostic finding in
to 60 minutes, with the blood being unable to clot.
defibrination coagulopathy.
Platelets are usually unaffected.
7. Fibrinogen degradation products grossly elevated
Snakebite coagulopathy can prove complex to manage, (XDP/d-dimer > 16) / (normal = <0.25). This is
and it is preferable to treat the patient in a major another key diagnostic finding.
hospital, with full coagulation laboratory facilities on site.
8. NOTE: Degradation products are in themselves
anticoagulant, and at such high levels may interfere
Tests for coagulopathy:
with some clotting tests, giving falsely high levels of
1. If there is no laboratory in your hospital, perform a abnormality, particularly INR and aPTT on some
whole blood clotting time (5 to 10 mL venous blood in automated coagulation machines. This may obscure
a glass tube, e.g. test tube, and observe time to clot; the first signs of recovery.
normal is less than 10 mins, if there is a coagulopathy
there will be no clotting at 15 minutes or only a very Management principles:
weak clot). However, performing a WBCT is not a
1. If initial studies are normal, remove PIB first aid and
substitute for laboratory coagulation tests and should
repeat studies after 2 hours, or sooner if the patient
only be used as initial assessment while transfer to a
appears envenomed.
hospital with laboratory facilities is being organised.
NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines PAGE 23

17. 2. If the second set of tests are also normal, repeat a hard to ascertain, and the whole blood clotting time
third time, a further 3 hours later. might be prolonged in these patients, though a clot
3. If there is a significant coagulopathy (unclottable blood, should eventually form, unlike true defibrination
or INR>2 + low fibrinogen), then this must be treated. coagulopathy, as discussed earlier.
4. Antivenom is the treatment of choice. Replacement Experience has shown that persistent ooze from the bite
therapy with clotting factors (e.g. whole blood, FFP, site or elsewhere is not likely as a result of venom
cryoprecipitate) should be avoided as it is liable to induced direct anticoagulation, again, different to
make the coagulopathy worse if there is still active defibrination coagulopathy. Brown Snakes, Tiger Snakes,
venom. Once active venom is all neutralised by Taipans and other species causing defibrination do not
antivenom normal homeostasis rapidly rectifies the cause this direct anticoagulation, as discussed earlier.
problem (sometimes within 3 hours), placing the
Antivenom is very effective at rapidly reversing direct
patient out of danger (i.e. INR <4), usually without
anticoagulation coagulopathy. Usually one vial of
need of any other treatment.
antivenom will suffice.
5. Antivenom therapy can be titrated against the
resolution of the coagulopathy, in particular, the
3.14.3 Snakebite myolysis
fibrinogen level. After the initial dose of antivenom
retest clotting studies at 3 and 6 hours after This occurs most commonly after bites by Tiger Snakes,
completion of antivenom dose. If still showing a non- Rough-scaled Snakes and Mulga Snakes/King Browns,
resolving coagulopathy at 6 hours (i.e. no significant but may also occur occasionally after Taipan bites, while
rise in fibrinogen level), it is usually necessary to give bites by Red-bellied Black Snakes and Spotted/Blue-
more antivenom and repeat tests as above, bellied Black Snakes may result in low level myolysis
continuing this process until there is evidence of (CK 500–3,000IU).
resolution, but if there is no resolution after an
It is the result of widespread direct damage to striated
adequate initial dose, then expert advice should be
muscle cells, resulting in complete muscle cell breakdown
sought to determine further dosing, rather than
within 1–3 days, though damage probably commences
giving ever increasing amounts of antivenom.
within 1–3 hours of venom reaching the muscle. Full
6. NOTE: even if enough antivenom has been given, recovery is possible, but will take 4+ weeks.
many coagulation parameters will remain abnormal
for hours or days, especially fibrinogen degradation The key diagnostic indicators are myoglobinuria (easily
products, which may remain elevated for 48 hours, mistaken for haematuria) and a dramatic rise in plasma CK.
longer if there is renal failure. A rise in fibrinogen The latter may reach figures much greater than
level from zero to detectable is the key indicator of 100,000IU. In addition, patients complain of generalised
resolution of the defibrination coagulopathy, not a muscle pain, with tender muscles.
return to normal fibrinogen levels, which may take
The secondary effects of myolysis are renal failure and
many hours. In some laboratories, the first evidence
massive hyperkalaemia, which can be very difficult to
of such a rise may be a fall in the aPTT or INR, rather
control and has proven lethal.
than a change in detectable fibrinogen titres.
Once myolysis is established it is uncertain if antivenom
3.14.2 Anticoagulation will reverse damage, but in severe cases it may be worth
trying further large doses of specific antivenom.
This occurs after some severe bites by Mulga Snakes,
Collett’s Snakes and possibly Spotted/Blue-bellied Black
3.14.4 Snakebite neurotoxic paralysis
Snakes and is due to direct anticoagulants in the venom,
which interfere with the extrinsic and, to a lesser extent, Presynaptic neurotoxic flaccid paralysis may occur after
the intrinsic clotting pathways. bites by Tiger Snakes, Rough-scaled Snakes,
Copperheads, Taipans, rarely Brown Snakes.
This can result in a prolonged clotting time, elevated INR
and aPTT, but fibrinogen levels and fibrinogen degradation It usually first manifests as ptosis, 1–3+ hours after the
products are within the normal range. The INR, in bite, with potential progression to partial ophthalmoplegia,
particular, may be grossly elevated, occasionally >12. complete ophthalmoplegia, fixed dilated pupils, dysarthria,
However, without a full clotting laboratory, this may be dysphagia, peripheral weakness, culminating in
PAGE 24 NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines

18. respiratory paralysis, though it may take 24+ hours to ■ Test for venom in urine using SVDK.
reach this final stage. Once complete paralysis is ■ If in doubt discuss with a Clinical Toxicologist or
established it may take days, weeks or longer to reverse Toxicologist at the NSW Poisons Information
sufficiently for the patient to survive off a ventilator. Centre on 131126 or your local Critical Care Referral
Antivenom will not reverse well established presynaptic Network.
paralysis.
Pure postsynaptic neurotoxic flaccid paralysis may occur 3.16 Management of the patient with
after bites by Death Adders, resulting in similar, but often no evidence of envenomation
more rapid progression of symptoms and signs. This form
of paralysis is usually reversible if sufficient antivenom is 3.16.1 Relevant history
given. Neostigmine may also reduce the degree of paralysis. ■ Was a snake seen to bite (?multiple bites) OR were
the circumstances such that a bite might have
3.14.5 Follow-up of snakebite patients occurred?
All patients with systemic envenoming should be ■ When did the patient get bitten (elapsed time)?
followed up over 6 months, with particular concern for ■ Description of snake if possible (colour, length).
serum sickness over the first 14 days.
■ Geographic location the incident occurred (snakes in
Consider giving a 7-day course of oral steroids as prophylaxis the area).
if more than 25 mLs of antivenom has been given. ■ Timing and type of first aid and activity after the bite.
It is important to follow up all patients with initially trivial ■ Determine if there has been any evidence of
or no apparent envenoming, especially if discharged less envenoming; specifically ask about headache,
than 24 hours post-bite, to ensure late onset envenoming nausea, vomiting, abdominal pain, blurred or double
is not missed. In particular, look for late onset neurotoxic vision, slurring of speech, muscle weakness,
envenoming, myolysis (not if proven Brown Snake bite) respiratory distress, bleeding from the bite site or
and renal damage. 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
3.15 Management of the severely ill consciousness, convulsions.
patient where diagnosis of
■ Relevant past history; specifically allergy or past
snakebite is obscure
exposure to antivenom, atopic history, renal, cardiac,
If the patient presents with unexplained onset of or respiratory disease.
collapse, convulsions, bleeding, paralysis, rhabdomyolysis
(e.g. muscle breakdown, myoglobinuria), or renal failure, 3.16.2 Examination
in a setting where snakebite might have occurred (e.g. in
Assess for:
rural areas, or gardens, paddocks, long grass in urban
areas), and particularly in children who may give no ■ Evidence of a bite (if there is an adequate first aid
history of exposure to snakes, then include snakebite in bandage in place, cut it away from over the bite site,
the differential diagnosis. keeping bandage away from area adjacent to skin
(DO NOT WASH WOUND; SWAB FOR VENOM
Useful tests to establish if there has been a snakebite
DETECTION) looking for evidence of multiple bites,
include:
or venom movement (i.e. swollen or tender draining
■ Examine patient on exposed areas for bite marks or lymph nodes).
scratches.
■ Neurotoxic paralysis (ptosis or drooping eyelids,
■ Whole blood clotting time or coagulation studies to diplopia or double vision, dysarthria or slurred
establish if there is a coagulopathy. speech, limb weakness, respiratory distress).
■ Check for myolysis manifested by dark or red urine ■ Coagulopathy (bleeding from bite site or elsewhere).
indicative of myoglobinuria (positive for “blood” and
■ Muscle damage (muscle tenderness, pain on
so may be mistaken for haematuria), elevated CK
movement, weakness, urine colour).
(>1000).
NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines PAGE 25

19. 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.
PAGE 26 NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines