First aid for snake bite
The fi rst aid currently recommended is based around the mnemonic ‘R.I.G.H.T’.
The details are provided in Table no.6 .
Table No. 6: Currently recommended First aid
• R. = Reassure the patient.
(70% of all snakebites are from non-venomous species. Only 50% of bites by
venomous species actually envenomate the patient)
• I = Immobilise in the same way as a fractured limb.
(Use bandages or cloth to hold the splints, not to block the blood supply or
apply pressure. Do not apply any compression in the form of tight ligatures,
they don’t work and can be dangerous!)
• G. H. = Get to Hospital Immediately.
(Traditional remedies have NO PROVEN benefi t in treating snakebite).
• T= Tell the doctor of any systemic symptoms such as ptosis that manifest on
the way to hospital.
This method will get the victim to the hospital quickly, without recourse to
traditional medical approaches which can delay effective treatment.
Traditional fi rst aid methods followed for snakebite:
The traditional methods such as application of tourniquet, cutting (incision) and
suction, washing the wound, snake stone or other methods have adverse effects and
hence, they have to be discarded. The mneumonic used to recall some of the traditional
methods followed is “WHISTTLE” and these are described below.
Washing the Wound:
Victims and bystanders have a tendency to wash the wound to remove any venom
on the surface. This should not be done as the action of washing increases the fl ow of
venom into system by stimulating the lymphatic system.
Household remedies:
Various forms of household remedies are applied to the site of bite which may
enhance absorption of venom
(Incision) Cutting and Suction:
Cutting the site of bite and suctioning incoagulable blood increases the risk of
bleeding to death as well as increases the risk of infection. Venom is not cleared or
removed from the snakebite site by this method.
Snake stone:
Snake stone is applied to the site of bite saying that it will absorb the venom and
falls once the venom is absorbed. This contributes to delay in seeking appropriate
health care.
Tourniquets:
Tight tourniquets made of rope, string and cloth, have been followed traditionally
to stop venom fl ow into the body following snakebite. The problems noticed with
tourniquets are :-
• Risk of ischemia and loss of the limb
• Risk of necrosis
• Risk of massive neurotoxic blockade
• Risk of embolism if used in viper bites.
• Release of tourniquet may lead to hypotension.
• Gives patient a sense of false security, which encourages them to delay their
journey to hospital
Thermal methods:
• Cautery treatment is followed in some areas. It is injurious and not
benefi cial
• Cryotherapy involving the application of ice to the bite was proposed in the
1950’s. It was subsequently shown that this method had no benefi t and merely
increased the necrotic effect of the venom.
Local application of anti snake venom:
Local application of anti snake venom has not shown any benefi cial effects
Electrical Therapy:
Electric shock therapy for snakebite received a signifi cant amount of press
coverage in the 1980’s. The theory behind it stated that applying an electric current tothe wound denatures the venom. Much of the support for this method came from letters
to journals and not scientifi c papers. It has been demonstrated that the electric shock
has no benefi cial effect and hence, it has been abandoned as a method of fi rst aid.
Pressure Immobilisation Method (PIM)
PIM was developed in Australia in 1974 by Sutherland and gained some supporters
on television and in the herpetology literature. Some medical textbooks have referred
to it. Further work done by Howarth demonstrated that the pressure, to be effective,
was different in the lower and upper limbs. The upper limb pressure was 40-70mm
of Mercury; the lower limb was 55-70mm of mercury. Work carried out by Norris
showed that only 5% of lay people and 13% of doctors were able to correctly apply
the technique. In addition, pressure bandages should not be used where there is a risk
of local necrosis, that is in 4/5 of the medically signifi cant snakes of India. In view of
the diffi culties encountered at every level, Pressure Immobilisation Method cannot be
recommended for use at present.
Newer Methods
‘Pressure Pad or Monash Technique’
Initial research has suggested that a ‘Pressure Pad or Monash Technique’ may have
some benefi t in the fi rst aid treatment of snakebite. This method should be subjected
to further research in India to assess its effi cacy. It may have particular relevance to
the Indian Armed Forces who carry Shell Dressings as part of their normal equipment,
and would thus be ideally equipped to apply effective fi rst aid in diffi cult geographic
settings where the need is great.
Treatment:
While dealing with a case of snake bite consider the mnemonic ‘RASI’.
• Remember principles ( “12 As” )
• Address the problems – clinical and social
• Seek help from others when required and
• Inform the patient and / or care givers on the status of illness, clinical course,
management, outcome, welfare measures and follow up clearly with empathy.
Principles involved in the management of snake bite
The principles while managing cases of snake bite at any Health Centre are clubbed
under “12 As”
Table No. 7: Principles involved in the management
1. Admit the victim immediately.
2. Ask effectively.
3. Assess quickly.
4. Act swiftly.
5. Administer medication meticulously.
6. Address to the wound properly.
7. Anticipate complications keenly.
8. Avoid errors carefully.
9. Ascertain the status repeatedly.
10. Amicable with patients and care givers and show empathy.
11. Advise on follow up accordingly.
12. Arrange for referral early.
1] Admit all victims of snake bite & Keep the victims under observation for 24 to 48
hours
2] Ask effectively to get the following –
a] Ask for the description of the snake, which has bitten the patient. If snake is
brought try to identify the snake with the help of snake picture chart.
b] Ask for the site of bite and check the site. Never be carried away, by bite marks
either for diagnosis or for assessment of severity.
c] Ask for the time of the bite and correlate with the progression of symptoms and
signs due to snakebite provided in page vide supra.
d] Ask for the details of traditional medicines or household remedies used, as it
may sometimes cause confusing symptoms or interfere with other drugs to be
administered.
3] Assess the following quickly.
a] Airway, Breathing and Circulation
b] Vitals HR, RR, BP and oxygen saturation by Pulse oximetry (if required)
c] Chest expansion, and the ability to put out the tongue beyond incisors and
counting the numbers at the bed side.
d] Site of snake bite along with regional lymphadenitis clinically from head to
foot as well as back
e] For associated co-morbid illness[es]
f] For consuming any medication[s]
g] The status of envenomation – local systemic (neurotoxic, hemotoxic, myotoxic)
or a combination of them
4] Act swiftly
a] Support Airway, Breathing and Circulation
b] Start IV line [fl uid for children refer to Annexure II –Table No.29]
c] Provide supportive measures depending upon the requirements including blood
transfusion / components if required.
d] Connect to ventilator if there is a need
5] Administer medications meticulously
a] Tetanus Toxoid injection intramuscularly
b] Anti snake venum as IV drip if needed – described vide infra
(ASV is composed of large molecules (IgG or fragments) and are absorbed
slowly via lymphatics, making the bioavailability by this route poor as
compared to intravenous administration. Also, intramuscular injections
are not preferred as it could cause pain on injection and risk of hematoma
formation and sciatic nerve damage in patients with hemostatic abnormalities.
Intramuscular injections should only be given in settings where intravenous
access cannot be obtained and / or the victim cannot be transported to a hospital
immediately).
c] Ionotropics as IV drip if required
d] Antimicrobials if necessary
e] IV fl uids as per need [fl uid for children refer to Annexure II – Table No.29]
f] Other supportive medications including medicines to relieve pain (avoid
aspirin) as per need.
6] Address to the wound properly
Remember the surigcal issues described vide infra and Table 11 in addition to the
following.
a] Wound following snake bite may show bite marks with or without laceration.
b] Sometimes venom may penetrate deep and hence deeper tissues may be
damaged which may not be visible during initial examination.
c] At the site of bite, bleb or vesicle may develop and end in the form of an ulcer
which is a non specifi c one. (Non-specifi c ulcers are defi ned as ulcers due to
infection of wounds, physical or chemical agents or due to local irritation).
d] Consider the following while managing the wound / ulcer.
• Minimize unnecessary blood loss
• Avoid the formation of a hematoma
• Initiate adequate cleaning with normal saline or tap water, debridement,
and edema control
• Remove debris and necrotic tissue, irrigate gently with water / normal
saline
• Expose viable tissues, excise eschar after controlling hemotoxic
complications
• Use topical antibacterial agents
• Apply dressings after complete debridement.
Maintain proper wound environment and prevent ischemia.
• Keep the bacterial count as low as possible.
• Facilitate healing of acute wound by applying non adherent dressing to
ensure adequate epithelialisation and to prevent contamination of the
wound.
• Keep wounds clean and dry.
• Avoid soaking or scrubbing the wound.
• Teach & explain the care of wound to the patients.
• Educate on good personal hygiene and nutrition.
• Control diabetes if identifi ed.
7] Anticipate complications keenly.
a] Examine the victims at regular intervals for alterations in symptoms and signs
b] Observe for anti snake venom related systemic changes and drug toxicity and
manage them as described vide infra under treatment for ASV reactions.
8] Avoid errors carefully while assessing the case, investigating the victims,
administering medications, following the case at hospital, undertaking any procedures,
referring to other specialists or hospital, communicating with patient / and care
givers, and planning for discharge as well as preparing reports, fi lling up the forms,
reviewing the data and conducting the audit.
9] Ascertain the status repeatedly and provide supportive measures as these cases
of snake bite victims may develop covert signs during hospital stay while on
treatment.
10] Amicable interaction with patient and care givers with empathy is essential in
view of the socio clinical aspects of snake bite.
11] Advise on follow up accordingly in view of the systemic toxicity and the nature of
wound following snake bite. Patients may be also motivated to attend the nearest
Health centre / Hospital for follow up care. Follow-up checks are required for
assessment of long term effects on different organs / systems and for appropriate
management wherever required / needed.
12. Arrange for referral early – One should also remember the criteria for referral and
provide clear instructions while referring the case. The details on referral aspects
of snake bite is provided vide infra in Table 15.
Pharmacological aspects of Anti snake venom
The goals of pharmacotherapy with injection Anti snake venom (ASV) are to
neutralise the venom, reduce morbidity and mortality, and prevent complications.
Currently available Anti Snake Venom (ASV) in India is polyvalent i.e., it is effective
against all the four common species; Russells Viper (Daboia russelii), Common
Cobra (Naja naja), Common Krait (Bungarus caeruleus) and Saw Scaled Viper (Echis
carinatus). Indian ASV is a F(ab)2 product derived from horse serum and has a halflife
of over 90 hours. Though it is purifi ed, it still can be immunogenic.
At present, no monovalent ASV is available primarily because there are no objective
means of identifying the snake species, in the absence of the dead snake. Moreover it
is diffi cult for the physician to determine which type of Monovalent ASV to employ
in treating the patient. In addition there are diffi culties to prepare, supply and maintain
adequate stock of species specifi c monovalent ASV.
There are other known species such as the Hump-nosed pitviper (Hypnale hypnale)
where polyvalent ASV is known to be ineffective. In addition, there are regionally
specifi c species such as Sochurek’s Saw Scaled Viper (Echis sochureki) in Rajasthan,
where the effectiveness of polyvalent ASV may be questionable. Further work has
to be carried out with ASV producers to address this issue of preparing ASV useful
against other poisonous snakes observed in India.
In India ASV is manufactured by Bengal Chemicals & Pharmaceuticals, Kolkata;
Bharat Serums, Mumbai; Biological Evans, Hyderabad; Central Research Institute,
Kausali; Haffkins Pharmaceuticals, Mumbai; King Institute of preventive medicine,
Chennai; Serum Institute, Pune and Vins bio-products, Hyderabad.
ASV is produced in both liquid and lyophilised forms. There is no evidence to
suggest which form is more effective and many doctors prefer one or the other based
purely on personal choice. Liquid ASV requires a reliable cold chain and refrigeration
and has a 2 years shelf life. Lyophilised ASV, in powder form, requires only to be kept
cool and hence, is useful in remote areas where power supply is inconsistent. The
details of pre hospital treatment and issues related to ASV may be recorded in the form
provided in Annexure IV.
ASV Administration
Criteria
ASV is prepared from animal and hence, it should only be administered when there
are defi nite signs of envenomation. Anti-Snake Venom carries risks of anaphylactic
reactions and should not therefore be used unnecessarily. Unbound, free fl owing
venom, can only be neutralised when it is in the bloodstream or tissue fl uid. Also it
is a scarce and costly commodity. Hence, ASV may be administered only if a patient
develops one or more of the following signs / symptoms.
Systemic envenoming
• Evidence of coagulopathy primarily detected by 20 WBCT or visible
spontaneous systemic bleeding, bleeding gums, etc., Further laboratory tests for
thrombocytopenia, Hb abnormalities, PCV, peripheral smear etc may provide
confi rmation, but 20 WBCT is paramount.
• Evidence of neurotoxicity: ptosis, external ophthalmoplegia, muscle paralysis,
inability to lift the head etc.,
• Cardiovascular abnormalities: hypotension, shock, cardiac arrhythmia,
abnormal ECG.
• Persistent and severe vomiting or abdominal pain.
Local envenomation (Refer Table No: 4)
Purely local swelling, even if accompanied by a bite mark from an apparently
venomous snake, is not grounds for administering ASV if a tourniquet or tourniquets
have been applied. These themselves can cause swelling. Once they have been removed
for 1 hour and the swelling continues, then it is unlikely to be as a result of the tourniquet
and administration of ASV may be justifi ed.
Dosage
In the absence of defi nitive data on the level of envenomation, symptomatology is
not a useful guide to the level of envenomation. Any ASV regimen adopted is at best
only an estimate. What is important is to establish a single guideline which could be
adhered to, in order to enable sensitization results to be reliably reviewed.
The recommended dosage level has been based on published research that Russells
Viper injects on average 63mg (SD 7) of venom. Logic suggests that our initial
dose should be calculated to neutralise the average dose of venom injected. This ensures
that the majority of victims should be covered by the initial dose and keeps the cost of
ASV to acceptable levels. The range of venom injected is 5mg to 147mg.
One vial of ASV neutralises 6mg of Russells Viper venom. So, to neutralize
63mg of venom, 10 vials are needed. Not all victims will require 10 vials as some may
be injected with less than 63mg. However, starting with 10 vials ensures that there is
suffi cient neutralising power to neutralise the average amount of venom injected and
during the next 12 hours to neutralise any remaining free fl owing venom.
Warrell et al based on their study have shown that test doses for ASV have no
predictive value in detecting anaphylactoid or late serum reactions and should not
be used. These reactions are not IgE mediated but Complement activated. They may
also pre-sensitise the patient and thereby create greater risk. For Neurotoxic / Anti
Haemostatic envenomation, 8 to 10 vials of ASV is recommended to be administered
as initial dose. Children receive the same ASV dosage as adults, as snakes inject the
same amount of venom into adults and children. The ASV is targeted at neutralising
the venom.
Administration
ASV may be administered in two ways over a period of one hour at a constant speed
and the patient should be closely monitored for 2 hours:
• Infusion: liquid or reconstituted ASV is diluted in 5-10ml/kg body weight
of isotonic saline or glucose and administered as infusion usually. (Fluid
requirement for children refer to Annexure II)
• Intravenous Injection: Rarely reconstituted or liquid ASV is administered by
slow intravenous injection. (2ml / minute). Each vial is 10ml of reconstituted
ASV.
Facts to be remembered before / while using of Anti Snake Venom (ASV)
1. ASV is available in a polyvalent form and marketed in liquid or lyophilised
preparations in 10ml vial / ampoule.
2. Remember to use and maintain cold chain systém for liquid form. Users are
informed to ascertain whether the cold chain is maintained.
3. There is no dose adjustment for ASV administration for children.
4. Before administering ASV, health staff should read and check the status of vial or
ampoule containing ASV.
5. Elicit history of prior exposure to ASV. If a patient had received ASV earlier
and comes back with features of snake envonemation again, he / she has to be
considered as a fresh case and treated accordingly. However, care should be taken
while administering ASV, since he / she has been sensitised.
6. ASV treatment should not be initiated without adequate agents for managing
anaphylaxis or anaphylactoid reaction.
7. Anaphylactic or late serum sickness cannot be determined or prevented by test
dose.
8. ASV neutralises the unbound venom, hence give it early.
9. ASV administration should not be delayed or denied on the grounds of anaphylactic
reactions to a deserving case.
10. ASV is required only to those who show defi nite signs and symptoms of
envenomation.
11. ASV should not be pushed as IV bolus or IM directly. ASV has to be administered
slowly as IV infusion in normal saline or glucose water over a period of one hour.
12. Local administration of ASV near the site of bite has been proven to be ineffective
and painful, and raises the intra-compartmental pressure, particularly in the digits.
Hence, it should not be adopted.
13. There is no prophylactic dose of ASV.
14. Total dose requirement cannot be decided on the basis of (WBCT) Whole blood
clotting test (or) clinical signs and symptoms.
15. Even if the patient develops reaction(s), the total dose required should be
administered slowly after the patient recovers from the reaction(s).
16. There is no other drug of choice other than ASV for the treatment of poisonous
snakebite.
17. The patient has to be closely monitored for manifestations of reactions to ASV for
atleast 2 hours continuously.
18. No interaction with ASV has been reported.
19. Fetal risk due to ASV has not been established or studied in humans.
20. Safety status for use of ASV during pregnancy has not been established.
21. Timely administration of ASV will not guarantee the recovery or protect the
individual from the venom induced toxicity or complications defi nitely.
ASV Reactions
* Reaction to ASV develop usually within 15 to 30 minutes or within 2 hours. So
monitor the case on ASV at 5min. interval for fi rst 30min. and then at 15min.
interval for two hours. The details of pre hospital treatment and issues related
to ASV may be recorded in the form provided in Annexure IV.
* Some times, anaphylaxis (Type I) following ASV may develop rapidly and
deteriorate into a life-threatening emergency, and hence anticipate and observe
for it in every case. If the correct guidelines are followed, anaphylaxis can be
effectively treated.
* Therefore get alert if the patient develops of any reactions to ASV as shown in
Table no: 8.
Table No. 8: Manifestations of immediate reactions to ASV
Itching (often over the scalp)
• Urticaria, even a single spot
• Nausea
• Vomiting
• Abdominal colic / pain
• Diarrhoea
• Tachycardia (PR >120/min) (for
children refer age specifi c chart)
• Fall in blood pressure
• Low volume pulse
Dry cough
• Bronchospasm / rhonchi
• Stridor (rarely)
• Angio-oedema of lips and mucous
membrane
• Fever
• Shaking chills (rigors)
• Sweating
• Cold and clammy skin
• Central cyanosis
• Febrile convulsions (in children)
• Anaphylaxis (Type I )
Treatment for ASV reactions
• Discontinue ASV
• Maintain IV line
• Administer Inj. Adrenaline 0.5ml of 1:1000 IM, (Adults) / Inj. Adrenaline
0.1ml/Kg body weight of 1:10,000 IM (paediatric dose). Details are provided
in Table no.9.
(If after 10 to 15 minutes the patient’s condition has not improved or is worsening,
a second dose of 0.5 ml of Adrenaline IM is given. This can be repeated for a third
and fi nal occasion but in the vast majority of reactions 2 doses of Adrenaline will
be suffi cient).
Studies have shown that adrenaline reaches necessary blood plasma levels in
8 minutes in the IM route, and in 34 minutes in the subcutaneous route . The early use
of adrenaline has been selected as a result of study evidence suggesting better patient
outcome if adrenaline is used early.
In extremely rare, severe life threatening situations, 0.5mg of 1:10,000 adrenaline
can be given IV slowly. This carries a risk of cardiac arrhythmias however, and
should only be used if IM adrenaline has been tried and the administration of IV
adrenaline is in the presence of ventilatory equipment and ICU trained staff.
Table No. 9: Dosage of adrenaline for adults and children
Adults
Inject adrenaline 1:1000 intramuscularly:
• Weighing < 50 kg give 0.25 ml
• Weighing 50 -100 kg give 0.50 ml
• Weighing >100 kg give 0.75 ml
*Children (upto 25 kg)
Inject adrenaline 1:10,000 dilute
1ampoule (1 ml) of adrenaline 1:1000
with 9ml water for injection or normal
saline.
Inject intramuscularly 1:10,000
adrenaline according to the guide
(approximates to 0.1ml/kg).
• 1 year (10 kg) give 1 ml
• 3 years (15 kg) give 1.5ml
• 5 years (20 kg) give 2ml
• 8 years (25 kg) give 2.5ml
• Children > 25 kg as for small
adults
Approximate body weight for children may be calculated by the formula;
• 2 x Age + 9 = weight in kg.
Start an adrenaline infusion if the patient remains shocked, (preferably via a
central venous line), commencing at 0.25 microgram/kg/minute, and titrating as
required to restore blood pressure. Large doses of adrenaline may be needed.
Consider additional measures:
• Administer Salbutamol or Terbutaline by aerosol or nebuliser (Beta2 agonists)
for bronchospasm.
• Antihistamines: Administer both H1 receptor blockers Inj. Chlorpheniramine
maleate 10 – 20mg as IV / intramuscularly or Promethazine 0.5 – 1mg/kg
and H2 receptor blockers Inj.Ranitidine 1mg/kg or Famotidine 0.4mg/kg or
Cimetidine 4mg/kg slowly intravenously.
• The dose for children is of Pheniramine maleate at 0.5mg/kg/day IV
or Promethazine HCl can be used at 0.3 – 0.5mg/kg IM or 0.2mg/kg of
Chlorpheniramine maleate IV, and 2mg/kg of Hydrocortisone IV, antihistamine
use in pediatric cases must be deployed with caution.
• Administer Corticosteroids intravenously: Hydrocortisone 2 – 6mg/kg or
Dexamethasone 0.1 – 0.4mg/kg
• Try nebulised Adrenaline (5ml of 1:1000) in case of laryngeal oedema which
often will ease upper airways obstruction. However, do not delay intubation if
upper airways obstruction is progressive.
• IV fl uids should be given for haemodynamic instability.
• Once the patient has recovered, the ASV can be restarted slowly for
10 – 15minutes, keeping the patient under close observation. Then the normal
drip rate should be resumed.
• Monitor vitals and provide supportive measures
Late Serum sickness reactions (delayed hypersensitivity) to ASV
Serum sickness may occur one to two weeks after administration of ASV. Late
Serum sickness reactions can be easily treated with an oral steroid such as prednisolone,
adults 5mg 6 hourly, paediatric dose 0.7mg/kg/day. (Duration of treatment has to be
adjusted with case). Oral H1 Antihistamines provide additional symptomatic relief.
Prevention of ASV Reactions – Prophylactic Regimens
The conclusion in respect of prophylactic regimens to prevent anaphylactic
reactions, is that there is no evidence from good quality randomized clinical trials to
support their routine use. If they are used then the decision must rest on other grounds,
such as policy in the case of hospitals, which may opt for a maximum safety policy,
irrespective of the lack of defi nitive trial evidence.
Two prophylactic regimens normally recommended are given below:
• 100mg of Hydrocortisone and H1 antihistamine (10mg Chlorphenimarine
maleate; or 22.5mg IV Phenimarine maleate IV or 25mg Promethazine
hydrochloride IM) 5minutes before ASV administration. The dose for children
is 0.1-0.3mg/kg of antihistamine IV and 2mg/kg of Hydrocortisone IV.
Antihistamine should be used with caution in pediatric patients.
• 0.25-0.3mg Adrenaline 1:1000 given subcutaneously.
If the victim has a known sensitivity to ASV, pre-medication with adrenaline,
hydrocortisone and anti-histamine may be advisable, in order to prevent severe
reactions.
Repeat Doses of ASV in Neurotoxic Envenomation
The ASV regime relating to neurotoxic envenomation has caused considerable
confusion. If on reassessment after 1 – 2hrs the initial dose has been unsuccessful in
reducing the symptoms / if the symptoms have worsened / if the patient has gone into
respiratory failure then a further dose should be administered. This dose should be
the same as the initial dose, i.e., if 10 vials were given initially then 10 vials should
be repeated for a second dose and then ASV is discontinued. 20 vials is the maximum
dose of ASV that should be given to a neurotoxically envenomed patient.
Once a patient in respiratory failure, has received 20 vials of ASV and is supported
on a ventilator, ASV therapy should be stopped. This recommendation is due to the
assumption that all circulating venom would have been neutralised by this point.
Therefore further ASV serves no useful purpose.
Evidence suggests that ‘reversibility’ of post synaptic neurotoxic envenoming is
only possible in the fi rst few hours. After that the body recovers by using its own
mechanisms. Large doses of ASV, over long periods, have no benefi t in reversing
envenomation.
Confusion has arisen due to some medical text books and journal articles
suggesting that ‘massive doses’ of ASV can be administered, and that there need
not necessarily be a clear-cut upper limit to ASV. These texts are talking about snakes
which inject massive amounts of venom, such as the King Cobra or Australian Elapids.
There is no justifi cation for massive doses of 50+ vials in India, which usually results
in the continued use of ASV whilst the victim is on a ventilator. No further doses of
ASV are required; unless a proven recurrence of envenomation is established.
Additional vials to prevent recurrence are not necessary.
Repeat Doses of ASV in Anti Haemostatic envenomation
In the case of anti haemostatic envenomation, the ASV strategy will be based around
a six hour time period. When the initial blood test reveals a coagulation abnormality,
the initial ASV amount will be given over one hour. No additional ASV will be given
until the next Clotting Test is carried out. This is due to the inability of the liver to
replace clotting factors within 6 hours.
After 6 hours a further coagulation test should be performed and a further dose
should be administered in the event of continued coagulation disturbance. This dose
should also be given over one hour. Clotting tests and repeat doses of ASV should
continue on a 6 hourly pattern until coagulation is restored, unless a species is identifi ed
as one against which Polyvalent ASV is not effective.
The repeat dose should be 5 -10 vials of ASV i.e., half to one full dose of the
original amount. The most logical approach is to administer the same dose again, as
was administered initially. Some, argue that since the amount of unbound venom is
declining, due to its continued binding to tissue, and due to the wish to conserve scarce
supplies of ASV, there may be a case for administering a smaller second dose. In the
absence of good trial evidence to determine the objective position, a range of vials in
the second dose has been adopted.
Recurrent Envenomation
When coagulation has been restored, no further ASV should be administered,
unless a proven recurrence of a coagulation abnormality is established. There is no
need to give prophylactic ASV to prevent recurrence. Recurrence has been a mainly
U.S. phenomenon, due to the short half-life of Crofab ASV. Indian ASV is a F(ab)2
product and has a half-life of over 90 hours, and therefore is not required in a prophylactic
dose to prevent re-envenomation
Anti Haemostatic Maximum ASV Dosage Guidance
The normal guidelines are to administer ASV every 6 hours until coagulation has
been restored. However, what should the clinician do after say, 30 vials have been
administered and the coagulation abnormality persists? There are a number of questions
that should be considered.
Firstly, is the envenoming species one for which polyvalent ASV is effective?
For example, it has been established that envenomation by the Hump-nosed pitviper
(Hypnale hypnale) does not respond to normal ASV. Coagulopathy can / may continue
for up to 3 weeks as in the case of Hypnale.
The next point to consider is whether the coagulopathy is resulting from the action
of the venom. Published evidence suggests that the maximum venom yield from say a
Russells Viper is 147mg, which will reduce the moment the venom enters the system
and starts binding to tissues. If 30 vials of ASV have been administered that represents
180mg of neutralising capacity, this should certainly be enough to neutralise free
fl owing venom. At this point the clinician should consider whether the continued
administration of ASV is serving any purpose, particularly in the absence of proven
systemic bleeding. At this stage the use of Fresh Frozen Plasma (FFP), cryoprecipitate
(fi brinogen, factor VIII) fresh whole blood, thrombocytes or coagulation factors can
be considered, if available. Plasmapheresis has been used successfully under such
circumstances amidst controversies. More clinical trails are warranted in these areas.
Recovery Phase
If an adequate dose of antivenom has been administered, the following responses may
be seen:
a) Spontaneous systemic bleeding such as gum bleeding usually stops within
15 – 30 minutes.
b) Blood coagulability is usually restored in 6 hours. (Principal test is
20 WBCT).
c) Post synaptic neurotoxic envenoming such as the Cobra may begin to improve
as early as 30 minutes after antivenom, but can take several hours.
d) Presynaptic neurotoxic envenoming such as the Krait usually takes a
considerable time to improve refl ecting the need for the body to generate new
acetylcholine emitters.
e) Active haemolysis and rhabdomyolysis may cease within a few hours and the
urine returns to its normal colour during the course of treatment.
f) Patients in shock blood pressure may increase after 30 minutes while on
treatment.
ASV risk and wastage
Defi nitive diagnosis and proper utilisation of ASV helps the patient. Otherwise
the patients are subjected to risk of receiving excessive / inadequate dosage of ASV.
More over the availability of ASV and doctors views and experience may infl uence the
utilisation of ASV for a given patient. Thus there is a possibility of fi rst aid wastage of
ASV. The details of provided in Table No.10.
Table No. 10: ASV – Risk and Wastage (Ian D.Simpson Model)
| Low wastage | High wastage | |
| High risk | ASV – Not available
– Insuffi cient administration |
ASV – Too little supply and species
are different |
| Low risk | Effective dose of ASV to
envenomed patients |
Receive ASV when not required
Too much ASV when not required Unnecessary ASV |