Snake Bite
Dr Ahmed Wayez MD Medicine Deptt. of Medicine
INTRODUCTION
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Snake bite is one of the major public health problems in the tropics.
It is also emerging as an occupational disease of agricultural workers.
In view of their strong beliefs and many associated myths, people resort to
magico –religious treatment for snake bite thus, causing delay in seeking
proper treatment.
SNAKE BITE INCIDENCES
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Papua New Guinea has some of the highest snakebite rates in the world, with the
country’s rural central province recording an annual incidence of 561.9 cases per 100
000 population
Snakebites are concentrated in mainly rural areas and vary considerably by season, with the peak incidence seen in the rainy and
harvesting seasons
Snake bite deaths worldwide
Epidemiology
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India is estimated to have the
highest snakebite mortality in the world.
Accoding to WHO: in India 50,000 deaths/yr
Males:Female- 2:1.
Majority of the bites being on the
lower extremities.
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Causes of mortality:
Not reaching health facility in time
Lack of awareness and knowledge
Harmful first aid practices
Lack of training among primary
care health workers
Snakes of India
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236 species
Only 13 are poisonous Of these four, namely
Common cobra ( Naja naja ),
Russell’s viper ( Dabiola russelii ),
Saw-scaled viper ( Echis carinatus ) and
Common krait ( Bungarus caeruleus ) Are believed to be responsible for
most of the poisonous bites in India.
Venomous v/s Non-venomous
Fang marks
Snakes of India
Common krait (Bungarus caeruleus): black or bluish black, with white crossbars
Snakes of India
Cobra ( Naja ): Hood, spectacle mark
RUSSELL’S VIPER ( Dabiola russelii )
Key identification feature is the black edged almond or chain shaped marks on the back
Saw-scaled viper (
Echis
carinatus
)PIT VIPER
wider head than neck and stocky body
rough scaled snake with large eyes,
DIAGNOSIS OF SNAKE BITE
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History
Fang Marks: classically, two puncture
wounds separated by a distance varying from 8mm to 4cm, depending on the
species involved.
However a side swipe may produce only a single puncture,while multiple bites could result in numerous fang marks.
20 whole blood clotting test (20WBCT)
20 Minute Whole Biood Clotting Test (20 WBCT)
Bedside, most reliable test of coagulation.
A few mililiter venous blood in a glass vessel
Left at room temperature for 20 minutes.
After 20 minutes tilt vessel gently, do not shake it.
If the blood is still liquid then the patient has incoagulable blood (clot test +).
Clot test +: repeat 6 hourly, to test for the requirement of repeat doses of ASV.
Clinical features
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Local features :
fang marks ,
severe pain/burning
swelling and discolouration,
discharge/ bleeding from bite site blister formation,
Species: Signs and Symptoms
Signs/Symptoms and Potential Treatments
Cobra Krait Russell’s
Viper Saw Scaled Viper
Other Vipers Local pain/ Tissue
Damage Yes No Yes Yes Yes
Ptosis/Neurotoxicity Yes Yes Yes! NO No
Coagulation No No Yes Yes Yes
Renal Problems No No Yes NO Yes
Neostigmine &
Atropine Yes No? No? NO No
Fang marks Persistent bleeding from fang marks 40min after bite of pit viper
Blistering at site of bite
Systemic features
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Krait,Cobra: Neurotoxicity
Pre-paralytic stage : Vomiting ,
Headache,
Paralytic stage :
Drooping eyelids
Difficulty in speaking/swallowing Difficulty in breathing
Systemic features
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Viper : Haemotoxic
Generalised bleeding manifestations.
Epistaxis,
Hemoptysis,
Bleeding gums Hematuria
Purpuric spots Renal failure
Shock
Systemic features
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Sea snake : Myotoxic
Muscle pain,
Muscle stiffness, Myoglobinuria
Urine output (Renal failure)
Management: First aid
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Mnemonic “CARRY NO R.I.G.H.T.”
CARRY = just carry the victim. Do not allow to walk even for a short distance
No - Tourniquate
No - Electrotherapy
No – Cutting, suctioning
No - Pressure immobilization
No- Nitric oxide donor (Nitrogesic ointment/
Nitrate Spray)
No- washing the bite site with soap or any other solution
Management: First aid
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R = Reassure the patient..
I = Immobilize in the same way as a fractured limb. Do not apply any
compression
G H = Get to Hospital Immediately. NO Traditional remedies
T = Tell the Doctor of any systemic
symptoms that manifest on the way of hospital.
PRESSURE IMMOBILISATION
Its purpose is to retard the movement of venom from bite site into circulation, thus buying time for the patient to reach
medical care.
Cont.
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Be prepared to treat the shock and provide cardiopulmonary resuscitation (CPR).
Get the victim to the nearest secondary or tertiary care hospital where antivenom can be provided
DO NOTS IN FIRST AID
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Do not apply a tourniquet.
Do not wash the bite site with soap or any other solution to remove the venom.
Do not make cuts or incisions on or near the bitten area.
Do not use electrical shock.
Do not freeze or apply extreme cold to the area of bite.
Do not apply any kind of potentially harmful herbal or folk remedy. .
Cont.
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Do not attempt to suck out venom with your mouth.
Do not give the victim drink, alcohol or other drugs.
Do not attempt to capture, handle or kill the snake and patients should not be taken to quacks.
Management: specific measures
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Anti snake venom (ASV):
Indications:
Neurotoxicity Haemotoxicity Shock
Total required dose will be between 10 vials to 30 vials usually.
Any hypersensitivity reaction should be dealt with adrenaline, steroids and anti histaminics
Ventilatory support if respiratory distress Hemodialysis- may be required
Anti-snake venom (ASV)
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Anti-snake venom (ASV)is the mainstay of treatment.
Antivenom is immunoglobulin [usually pepsin- refined F(ab’)2 fragment of whole IgG] purified
from the plasma of a horse, donkey or sheep that has been immunized with the venoms of one or more species of snake.
In India, polyvalent ASV, i.e. effective against all the four common species; Russell’s viper,
common cobra, common Krait and saw-scaled Viper and no monovalent ASVs are available
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Antivenom treatment should be given as soon as it is indicated.
It may reverse systemic envenoming even when this has persisted for several days or, in the case of haemostatic abnormalities, for two or more weeks.
20WBCT done 6 hourly
It is, therefore, appropriate to give
antivenom for as long as evidence of the coagulopathy persists.
HOW LONG ASV CAN BE GIVEN?
ROUTE?
Freeze-dried (lyophilized) antivenoms are reconstituted,
usually with 10ml of sterile water for injection per ampoule.
Two methods of administration are recommended:
(1) Intravenous “push” injection: Reconstituted freeze-dried antivenom is given by slow intravenous injection(not more than 2 ml/minute).
(2) Intravenous infusion: Reconstituted freeze-dried
antivenom is diluted in approximately 5-10 ml of isotonic fluid per kg body weight) and is infused at a constant rate over a period of about one hour
Patients must be closely observed for at least one hour after starting intravenous antivenom administration, so that early anaphylactic antivenom reactions can be
detected and treated early with epinephrine(adrenaline)
Cont.
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Local administration of ASV is not
recommended as it is extremely painful and can raise the intracompartmental pressure.
Intramuscular inj are not recommended because
Slow absorption by I/M route.
Bioavailability is poor, adequate plasma concentration not achieved
Pain at injection site and
Risk of haematoma formation
Anti-snake Venom Administration
INDICATIONS
Evidence of systemic toxicity.
Hemodynamic or respiratory instability
Hypotension, respiratory distress Hemotoxicity
Clinically significant bleeding or abnormal coagulation studies Neurotoxicity
Any evidence of toxicity usually beginning with CN abnormalities and progressing to descending
paralysis including diaphragm Evidence of local toxicity
Progressive soft tissue swelling
TEST DOSE
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Anti-snake Venom Test Dose NOT recommended
Test doses have not been shown to be
predictive of anaphylactic reaction or late serum sickness.
DOSE of ASV
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Total required dose will be between 10 vials to 30
vials usually, as each vial neutralizes 6mg of Russells Viper venom.
Starting with 10 vials ensures that there is sufficient ASV to neutralize the average amount of venom
injected and any remaining free flowing venom during the next 12 hours.
Even in the large study from south India, the amount of ASV exceeded 50 vials in some patients.
So decision of the treating physician is of utmost importance, because the guidelines may not be useful for all patients.
Response to initial dose of ASV
: If an adequate dose of appropriate antivenom has been administered, the following responses may be observed.
(a) General: The patient feels better. Nausea, headache and generalised
aches and pains may disappear very quickly. .
(b) Spontaneous systemic bleeding (e.g. from the gums): This usually stops within 15-30 minutes.
(c) Blood coagulability (as measured by 20WBCT): This is usually restored in 3-9 hours.
(d) In shocked patients: Blood pressure may increase within the first 30-60 minutes and arrhythmias such as sinus bradycardia may
resolve.
(e) Neurotoxic envenoming (cobra bites)
may begin to improve as early as 30 minutes after antivenom, but usually takes several hours.
(f) Active haemolysis may cease within a few hours and the urine returns to its normal colour
REPEAT DOSES
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Criteria for giving more antivenom
Persistence or recurrence of blood incoagulability after 6 hours(measured by 20WBCT) or of bleeding after 1-2 hours.
Deteriorating neurotoxic or cardiovascular signs after 1-2 hours of administering intial dose of ASV Maximum dose of ASV is around 50 vials.
ASV should be administered over a period of 1hour.
In hemotoxic envenomation;
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Once initial dose has been administered over one hour,
In patients who continue to bleed briskly, the dose of antivenom should be repeated within 1-2 hours.
20WBCT test every 6 hours
If positive, repeat dose of ASV.
This is based on the observation that, if a large dose of antivenom (more than enough to neutralize the venom procoagulant enzymes) is given initially, the time taken for the liver to restore coagulable levels of fibrinogen and other clotting factors is 3-9 hours This reflects the period the liver requires to restore clotting factors.
In Neurotoxic envenomation
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Antivenom treatment alone cannot be relied
upon to save the life of a patient with bulbar and respiratory paralysis
Death may result from Aspiration,
Airway obstruction or Respiratory failure.
A clear airway must be maintained.
Once there is loss of gag reflex and pooling of secretions in the pharynx, failure of the cough reflex or respiratory distress, a cuffed
endotracheal tube or laryngeal mask airway should be inserted
Neostigmine test.
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Should be performed in every patient with neurotoxic envenoming
Atropine sulphate (0.6 mg for adults; 50 μg/kg for children) or glycopyrronium is given by intravenous injection followed by neostigmine bromide by
intramuscular injection (0.5-2.5 mg for adults, 0.04 mg/kg for Children.)
The patient is observed over the next 30-60 minutes
(neostigmine) or 10-20 minutes (edrophonium) for signs of improved neuromuscular transmission.
Ptosis may disappear and ventilatory capacity (peak flow, FEV-1 or maximum expiratory pressure) may
improve.
If positive institute regular atropine & neostigmine.
Treatment of hypotension and shock
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Snake bite causes of hypotension and shock.
Anaphylaxis Vasodilatation Cardiotoxicity Hypovolaemia
Antivenom reaction Respiratory failure
Acute pituitary and adrenal insufficiency Septicaemia
Treatment- a selective vasoconstrictor such as dopamine may be given by intravenous infusion, preferably into a
central vein (starting dose 2.5-5mcg/kg/minute).
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Adverse reactions to anti-snake venom
Fear of potentially life threatening adverse
reactions causes reluctance amongst some to treat snakebite.
However, if handled early and with the primary drug of choice, these reactions are easily managed.
Patients should be monitored closely as there is evidence that many anaphylactoid reactions go unnoticed
Adverse reactions to anti-snake venom
At the first sign of any of the following:
Urticaria, itching, fever, shaking chills, nausea, vomiting, diarrhea,
abdominal cramps, tachycardia, hypotension, bronchospasm and angio- oedema:
1. ASV should be discontinued
2. 0.5 mg. of 1:1000 adrenaline should be given IM
The pediatric dose is 0.01 mg/kg body weight of adrenaline IM.
Evidence shows that adrenaline reaches necessary blood plasma levels in 8 minutes via the IM route, but up to 34 minutes in the subcutaneous route.
Treatment of adverse reactions to anti-snake venom
100 mg of hydrocortisone and 10 mg of H1 antihistamine will be administered IV.
The dose for children is 0.2 mg/kg of antihistamine IV and 2 mg/kg.
If after 10 to 15 minutes the patient’s condition has not improved or is worsening, second dose of 0.5 mg of adrenaline 1:1000 IM is given.
This can be repeated for a third and final occasion but in the vast majority of reactions, 2 doses of adrenaline will be sufficient.
Once the patient has recovered ASV can be restarted
Given slowly for 10-15 minutes (under close monitoring) Then the normal drip rate should be resumed
FOLLOW-UP
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After discharge from hospital, victim should be followed.
If discharged within 24 hours, patient should be advised to return if there is any worsening of
symptoms such as bleeding, pain or swelling at the site of bite, difficulty in breathing, altered
sensorium, etc.
The patients should also be explained about
serum sickness which may manifest after 5–10 days
