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 following Death 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
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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.
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
NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines PAGE 11
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
PAGE 12 NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines
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
NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines PAGE 13
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
PAGE 14 NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines
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
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.
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
NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines PAGE 17
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.
PAGE 18 NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines
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).
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.
NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines PAGE 21
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
PAGE 22 NSW HEALTH Snakebite and Spiderbite Clinical Management Guidelines
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