Snake bite basics in a visually appealing format for general population, school and college students, medical students, paramedics, nurses, and pg residents. Snakes included only pertaining to indian subcontinent. Any medical data given is valid only for indian subcontinent.
11. Poisonous
2. Head Scales are usually small in vipers, maybe large in pit
vipers. In Cobras and Coral Snakes third labial touches eye
and nasal shield. In Kraits there is no head pit and third labial
does not touch nose and eye.
NON POISONOUS - Usually large head scales, except in above.
16. Overhanging tree
branches serve as a
conduit for snakes.
Cracks and holes in
masonry is where
snakes lurk in plenty.
Using a mosquito net
can prevent snakes
falling from roof
directly on a person.
17. Snakes feast on frogs
and rodents.
Water bodies harbor
frogs which in turn
attract snakes.
Piles of rubble lying
undisturbed are liable
to harbor snakes.
18. Use a torch when
going outdoors at
night.
Wear high ankle boots
while on exercise.
Do not go out without
proper footwear in a
camp.
22. Either because of mechanical inefficiency or the snake’s control of
venom discharge, a proportion of bites by venomous snakes does not
result in the injection of sufficient venom to cause clinical effects.
Dry Bites
23. Rapid primary clinical assessment and resuscitation:
ABCDE approach
● Airway
● Breathing (respiratory movements)
● Circulation (arterial pulse)
● Disability of the nervous system (level of consciousness)
● Exposure and environmental control (protect from cold, risk of drowning
etc.)
24. Early clues that a patient has severe envenoming:
● Snake identified as a very dangerous one.
● Rapid early extension of local swelling from the site of the bite.
● Early tender enlargement of local lymph nodes, indicating spread of venom in the lymphatic
system.
● Early systemic symptoms: collapse (hypotension, shock), nausea, vomiting, diarrhoea, severe
headache, “heaviness” of the eyelids, inappropriate (pathological) drowsiness or early
ptosis/ophthalmoplegia.
● Early spontaneous systemic bleeding.
● Passage of dark brown/black urine.
25. Local signs of envenoming
Fang marks
Blistering
Persistent local bleeding
30. Do not assume that snake
bitten patients are unconscious
or even irreversible
“brain dead”
just because their eyes are
closed, they are
unresponsive to painful stimuli,
are areflexic, or have fixed
dilated pupils.
They may just be paralysed!
45. 20-minute whole blood clotting test
● If the blood is still liquid (unclotted) and runs out, the patient has hypofibrinogenaemia
(“incoagulable blood”) as a result of venom-induced consumption coagulopathy.
● In the South-East Asia region, incoagulable blood is diagnostic of a viper bite
and rules out an elapid bite.
● If the vessel used for the test is not made of ordinary glass, or if it has been cleaned with
detergent, its wall may not stimulate clotting of the blood sample (surface activation of factor XI
– Hageman factor) and test will be invalid If there is any doubt, repeat the test in duplicate,
including a “control” (blood from a healthy person such as a relative)
46. Other tests
● WBC Count - An early neutrophil leucocytosis is evidence of systemic envenoming.
● Platelet count - May be decreased.
● PBS - Helmet cells/Schistocytes
● Plasma - discolored due to hemoglobinemia/myoglobinemia
● ABG - eveidence of respi failure.
● Biochemistry - generalized muscle damage picture, renal failure, raised liver enzymes
● Urine - immunoassays can separate hemoglobin and myoglobin
52. Antivenom should be given only
to patients in whom its benefits
are considered likely to exceed its
risks. Since antivenom is
relatively costly and often in
limited supply, it should not be
used indiscriminately. The
risk of reactions should always be
taken into consideration.
53. Indications for antivenom
Antivenom treatment is recommended if and when a patient with proven or suspected snake-bite
develops one or more of the following signs:
● Systemic envenoming
● Haemostatic abnormalities: Spontaneous systemic bleeding (clinical), coagulopathy (20WBCT
or other laboratory tests such as prothrombin time) or thrombocytopenia (<100 x 109/litre or
100 000/cu mm) (laboratory).
● Neurotoxic signs: ptosis, external ophthalmoplegia, paralysis etc (clinical).
● Cardiovascular abnormalities: hypotension, shock, cardiac arrhythmia (clinical), abnormal
ECG.
54. Indications for antivenom
● Acute kidney injury (renal failure): oliguria/anuria (clinical), rising blood creatinine/ urea
(laboratory).
● (Haemoglobin-/myoglobin-uria:) dark brown urine (clinical), urine dipsticks, other evidence of
intravascular haemolysis or generalised rhabdomyolysis (muscle aches and pains,
hyperkalaemia) (clinical, laboratory).
● Supporting laboratory evidence of systemic envenoming (see above).
55. Indications for antivenom
● Local swelling involving more than half of the bitten limb (in the absence of a tourniquet) within
48 hours of the bite. Swelling after bites on the digits (toes and especially fingers).
● Rapid extension of swelling (for example, beyond the wrist or ankle within a few hours of bite on
the hands or feet).
● Development of an enlarged tender lymph node draining the bitten limb
56. ● 2 vials initial bolus
dose ?
● Infuse 5-10 vials in
NS/DNS (250-500
mL) over 1 hour
● Infuse at 2ml/min
● More vials
depending on
envenomation
● Sensitivity tests
NOT recommended
● No benefit of local
infiltration
57. Skin and conjunctival “hypersensitivity” tests will reveal IgE
mediated Type I hypersensitivity to horse or sheep proteins.
However, since the majority of early (anaphylactic) or late
(serum sickness type) antivenom reactions result from
direct complement activation rather than from IgEmediated
hypersensitivity, these tests are not predictive.
Since they may delay treatment and can in themselves be
sensitising, these tests should not be used !
58. At the earliest sign of a reaction:
● Antivenom administration must be temporarily suspended.
● Epinephrine (adrenaline) (0.1% solution, 1 in 1,000, 1 mg/ml) is the effective treatment for early
anaphylactic and pyrogenic antivenom reactions.
59. Snakes inject the same dose of venom into children and
adults.
Children must therefore be given exactly the same dose of
antivenom as adults.
60. ● Artificial ventilation
is necessary if
patient shows any
sign of paralysis
● A trial of
anticholinesterase
should be
performed in all
patients with
neurotoxic signs.
● Atropine sulfate, or
glycopyrronium
followed by
Neostigmine
61. Detection of kidney
injury:
• dwindling or no urine
output
• rising blood
urea/creatinine
concentrations
• clinical “uraemia
syndrome”