Snakebites are a common hazard in
, especially in rural areas. The morbidity and mortality of snakebites add significantly
to the health care cost of the country. The venomous snakes found in
Krait (Bungarus caeruleus)
Krait (Bungarus ceylonicus)
viper (Duboia russelli)
scaled viper (Echis carinatus)
snakes (Pelamis sp., Hydrophis
nosed viper (Hypnale hypnale)
pit viper (Trimeresures trigonocephalus)
The first six snakes are considered to be highly venomous
and the latter one is moderately venomous. Since recently, the morbidity and mortality
of hump nosed viper bites is more appreciated, especially with regard to acute renal
failure following bites. Its role as a moderately venomous snake is reconsidered.
Management of snakebites
The approach in management of snakebites can be summarized
- First aid treatment
- Transport to hospital
- Rapid clinical assessment and resuscitation
- Detailed clinical assessment and species diagnosis
- Investigations/ laboratory tests
- Antivenom treatment
- Supportive / ancillary treatment
- Treatment of chronic complication
The recommended first aid treatment for any snakebite
includes, reassurance, removal all rings, bracelets from the bitten part of the
body, washing the bitten area with soap & water, Keeping the stricken limb below
the level of heart and Immobilizing the bitten limb with a splint or a sling.
Medical help should be sought as soon as possible.
Things that are not recommended to do in event of a
snakebite include; making cuts or incisions at bite site, ‘sucking out’ venom from
wound, applying ice packs to bitten area, use of conventional tourniquet, taking
alcohol, herbal medicine or Aspirin for pain relief
Transport to hospital
Transport to hospital should be safe and quick as possible.
Any mode of transport such as bicycle, cart, motor vehicle, train or boat should be
used or patient should be carried. However it is important to reduce any movement
of the victim while transporting to avoid systemic absorption of the venom.
ill patient can present to the emergency care unit of the hospital with any of the
following complications of snakebite.
In such situations, immediate resuscitation with attention to airway, breathing
and circulation (A,B,C) is carried out in line with emergency life support guidelines.
This may include, clearing and maintaining airway, Ambu
bag and mask ventilation or ventilation with intubation, establishing IV access
and correcting any circulatory deficit.
assessment and identification of snake
The next step
is detailed clinical assessment of the patient. The most important aim in this step
is to identify the snake. Correct clinical identification of the snake is important
because; features of envenomation vary from species to species,
it helps to anticipate and prevent complications and decision to give antivenom is helped by correct identification
as many harmless snakes may look like venomous snakes. Furthermore, experience tells
that description by witnesses are unreliable.
can be done in several ways
the dead snake
detection by ELISA technique
approach’ – clinical syndromes
public education measures via mass media, the general population is knowledgeable
on what to do in event of snakebite. On many occasions they bring the snake to hospital.
All medical professionals in the country are trained to identify the venomous snakes
and many continuous medical education programmes are carried out in this regard
by the authorities. Antigen detection by ELISA is expensive and given the frequency
of snakebites, it is not cost effective to be used in routine hospital management
other than for research purposes.
When the biting snake is not physically available for
diagnosis, the syndromic approach and the circumstances of bite can be used to identify
the snake. (annexure 1)
The routine investigations that will help in assessment
of patient and performed at hospital setting include;
analysis (UFR – haemoglobin/ myoglobin)
rate / Tidal volume / Blood gas analysis
charting should be done daily
The 20 minute
whole blood clotting (20WBCT) test is a simple bedside test that detects haemotoxicity
of envenoming. (See annexure 2). A correctly performed 20WBCT with a positive result
i.e. incoagulable blood at 20 minutes is itself an indication to give antivenom
If the snake
identified as a venomous one and if there is a clear cut indication, the next step
in management is to start antivenom therapy. The antivenom currently used in Sri
Lankan hospitals is imported from India, Haffkine Institute, Mumbai or Serum
Institute of India, Pune, Vins Bioproducts, Hydrabad,
It is an equine
serum F(ab’)2 fragment raised against the venom of Indian Russell’s viper,
Common krait, Cobra and Saw scaled viper. It is not effective against hump nosed
for antivenom treatment are;
abnormalities: spontaneous systemic bleeding (clinical) coagulopathy(20WBCT or other
laboratory evidence) or thrombocytopaenia (<100/ul) (laboratory)
signs: ptosis, external ophthalmoplegia, paralysis etc. (clinical)
abnormalities: hypotension, shock, cardiac arrhythmia(clinical) abnormal ECG
renal failure: oliguria/anuria (clinical) rising blood creatinine/ urea (laboratory)
dark brown urine(clinical),urine dipsticks, other evidence of intra vascular haemolysis
or generalized rhabdomyolysis
aches &pain , hyperkalaemia) (clinical,laboratory)
laboratory evidence of systemic envenoming
(minimum dose – 10 vials, each diluted in 10ml of distilled water with 200ml of
normal saline, infused intravenously over 1 hour) itself carries a risk of adverse
reactions including anaphylaxis and hence should only be used where there is a clear
indication. Adrenaline and other medication such as Chlorpheniramine and hydrocortisone
is drawn up and kept at bedside during antivenom infusion. Emergency life support
equipment is also kept at hand. Patients frequently develop minor reactions to antivenom.
In such instances, the infusion is slowed or temporarily halted. The same dose of
antivenom is used in children as the snakes inject same amount of venom to both
children and adults. Antivenom should not be withheld in pregnancy.
to antivenom can be gauged with following observations;
General; feels better,
nausea, headache etc may disappear very quickly
stops within 15-30 minutes
is usually restored in 3-9 hrs
- post synaptic type may begin to improve in 30 min to several hrs, - pre synaptic
type unlikely to respond in this way
haemolysis & rhabdomyolysis responds in few hours & urine returns to normal colour
BP may increase within the first 30-60 min
give more antivenom include;
or recurrence of blood incoagulability after 6 hours or bleeding after 1-2 hours
neurotoxic or cardiovascular signs after 1-2 hours
It should be
noted that neurotoxic features with envenoming by elapid snakes such as Cobra or
Krait may not improve immediately after the initial dose of antivenom. Overtime
it will improve gradually without further antivenom therapy.
in management with regard to specific snakes
with very minimal local envenoming is the hallmark of Krait bites. The severity
varies from ptosis, ophthalmoplegia, muscle weakness to respiratory paralysis and
death. Respiratory support in form of intubation and ventilation is often necessary.
Therefore it is important to transfer the patient to a centre where ICU facilities
predominantly cause severe local envenoming and neurotoxicity. Haematological manifestations
are not seen. In addition to respiratory support surgical debridement of the bite
site may be necessary.
(Russell’s and Saw scale viper bites)
and local effects are seen with viper bites. Russell’s viper venom is also known
for its neurotoxic, myotoxic
and nephrotoxic features. The neurotoxicity is often
not severe as in envenoming by elapid snakes.
Hump nosed viper
It causes significant
morbidity in urban, semi-urban areas. In acute stage, local effects at bite site
and nephrotoxicity with acute renal failure are seen. Overtime chronic complications
such as amputations, multiple wound debridements, chronic renal failure is seen.
Indian polyvalent antivenom is completely ineffective (Trans R Soc Trop Med Hyg
2007,2008) against hump nose viper venom. Only recommended treatment is conservative
management which includes prevention of renal failure and management of renal failure
if prevention fails.
with analgesics such as paracetamol and tetanus toxoid is recommended following
snakebite. Local effects of toxins can result in muscle necrosis, gangrene, non
healing wounds and compartment syndrome requiring surgical intervention.
following snakebite is both psychological and physical. Patient education, physiotherapy
and occupational therapy are necessary for patients with amputations and prolonged
periods of immobilization.
is put on prevention of snakebites in
. Programmes at schools, community centres and via mass media are used to educate
people on prevention of snakebite.
Dr. C.A. Gnanathasan
30 October 2008
1: Syndromic approach to identification of snakes
Minute whole blood clotting test
Place a few milliliters
of freshly sampled venous blood in a small glass vessel
Leave undisturbed for
20 min at ambient temperature
Tip the vessel once
If the blood is still
liquid (unclotted) and runs out, the patient has hypofibrinogenaemia (incoagulable
blood) as a result of venom induced consumption coagulopathy