1. SNAKE BITES/scorpion stings
Snake bite is common life-threatening in many countries.
Farmers, hunters, rice-pickers are at particular risk
Prompt medical treatment is vital.
3-5 million victims /year, 50 000 deaths , 400 000 amputations.
40% of bites do not produce signs of envenoming.
It is difficult to predict which bites will produce symptoms or
the clinical outcome, all victims should be brought under
medical care as quickly as possible.
Poisonous species of snake fall into the families.
Snake venoms are complex mixtures of proteins & small
polypeptides with enzymatic activity.
Snake venoms are neurotoxins, haematotoxins (haemorrhagic
or coagulopathic) or cardiotoxins often occur in combination.
2. Clinical features & assessment
Key questions to ask a victim are:
The body part bitten?
How long ago?
What sort of snake?
Friends / relatives will frequently bring the snake with the
patient; it should be handled as little as possible since it may
only be injured rather than dead.
The amount of venom injected via a bite is highly variable,
depending on the length of time since the snake last ate& its
aggression.
Snake venom detection kits are available in some countries.
3. Clinical features & assessment
The venom is detected from a dry swab of the bite site using
monoclonal antibody techniques.
The 20-minute whole blood-clotting test is a useful bedside
tool in remote areas; a 2-3 ml sample of venous blood from the
victim is left undisturbed at ambient temperature for at least
20 minutes.
The vessel containing the blood is then tipped once & may be
compared with a normal control.
If it has not clotted, there is haemostatic disturbance from
systemic envenoming.
All patients should have a full blood count, urea/electrolytes,
liver function tests, creatine kinase, troponins, ECG.
6. Management:
Reassuring the patient
Immobilising the bitten area to minimise venom spread
Identifying the snake.
Application of a firm bandage to occlude lymphatic drainage
is appropriate, but tourniquets are unhelpful since they do not
prevent the spread of venom & frequently applied incorrectly.
Incisions at the bite site &attempts to suck out the venom by
mouth should not be made.
A large-bore IV cannula inserted on an unaffected limb.
BP, coagulation,renal, neurological, cardiorespiratory status
must be monitored, as hypotension, anaphylactic shock, renal
failure, respiratory distress may develop rapidly.
7. Management:
All patients with suspected envenoming should be observed
for 12-24 hours, as the initial manifestations may be delayed,
especially with elapid bites.
Pain/ vomiting should be managed symptomatically.
Aspirin should not be used ,may aggravate bleeding.
In severe coagulopathy with thrombocytopenia causing DIC,
large quantities of fresh frozen plasma, cryoprecipitate ,
platelets are required if the response to antivenin is poor.
The most appropriate therapy is timely administration of the
species-appropriate antivenin when indications.
Before starting antivenin, ask about history of allergy &
intradermal sensitivity test performed by injecting 0.02 ml of
saline-diluted antiserum at a site distant from the bite.
8. Management:
The inj site is observed for at least 10 mins for the redness,
hives, pruritus or other adverse effects.
The shorter the interval between inj & reaction, the greater
the degree of sensitivity.
0.5 ml 1:1000 adrenaline must be available when antiv given
A negative skin test does not rule out a reaction following
administration of the full antivenin dose.
The rate antivenin should be based on the severity of the
case& the patient's tolerance to the antivenin.
The entire initial dose should be given as soon as possible
within 4 hours of the bite.
In severe envenoming, antivenin given up to 24 hours after the
bite has been shown to reverse coagulation deficits.
9. Management:
INDICATIONS FOR ANTIVENIN ADMINISTRATION IN
SNAKE BITES
Cardiogenic shock
Spontaneous systemic bleeding
Incoagulable blood
Neurotoxicity
Haematuria
Other evidence of haemolysis/rhabdomyolysis
Rapidly progressive extensive local swelling
Bites on digits by snakes with known necrotic venoms
10. SNAKE BITES
There are three types of antivenin reaction:
Early anaphylactoid
Pyrogenic
Late.
If an immediate anaphylactoid reaction occurs,
administration of antivenin should be immediately
discontinued &the patient given an oral antihistamine or IM
adrenaline ( 0.5 ml of 1:1000) as appropriate.
Infusion of the antivenin can be restarted, but at a slower rate.
Corticosteroids are commonly given to treat serum sickness,
although their value remains to be established.
Bites by large snakes may need relatively high antivenin doses,
particularly in children or small adults.
11. SNAKE BITES
Additional antivenin (e.g. the contents of 1-5 vials) should be
administered if swelling progresses or if systemic features of
envenoming increase in severity & new manifestations such as
hypotension or reduced haematocrit appear.
The use of ancillary drugs, such as anticholinesterases for
neurotoxic envenoming, remains contentious.
If pulses are lost in a bitten limb, compartment syndrome
should be suspected & surgical assessment requested.
Wound débridement& later skin grafting are occasionally
required, especially in cobra & viper bites, but should never
be carried out until the coagulation profile is normal.
Awareness &avoidance of the habitat of snakes are the major
means of preventing snakebite.
14. SCORPION STINGS
The most important venomous animals after snakes.
Most scorpion species produce a venom which causes only
minor local reactions in humans, but in Mexico, Tunisia,
Algeria, Morocco, Libya scorpion stings are a serious health
hazard.
Scorpions do not attack humans& escape when disturbed.
Stings occur after a person accidentally steps on or
involuntarily presses the scorpion (when it is trapped inside
shoes or clothes) or when reaching under dead wood or stones.
Clothes / shoes need to be inspected closely & shaken& sitting
or sleeping places checked when camping in rural districts
where scorpions are common
15. SCORPION STINGS
Two types of scorpion venom exist:
1.Venom of genera Hadrurus, Vejovis, Uroctonus only effects,
including sharp burning, swelling, discoloration,very rarely,
anaphylaxis.
In envenoming by more poisonous species, Leiurus, common
in the M. East, systematic manifestations develop, transfer to
ICU required.
2. Venom, of genera of the poisonous varieties of
Centruroides / Mesobuthus, contains neurotoxins block sodium
channels& leads to spontaneous depolarisation of
parasympathetic &sympathetic nerves results in tachycardia,
hypertension, sweating, piloerection, hyperglycaemia & pulm
oedema (esp Mesobuthus species)& seizures.
16. SCORPION STINGS
The sharp pain after a sting is quickly followed by
paraesthesiae& numbness in the area due to peripheral nerve
effects, muscle fasciculation& finally drowsiness.
With Centruroides& Mesobuthus there is no swelling at the
sting site.
17. SCORPION STINGS: Management
Local pain & paraesthesiae are best treated with local
compresses & oral analgesics.
Patients with significant envenoming should be hospitalised
for at least 12 hours& observed for cardiovascular /
neurological sequelae.
More severe symptoms may require airway support& 1-2
vials of IV antivenin.
The effectiveness of antivenin is controversial, but it is
beneficial in the very young, the elderly or those with severe
hypertension.
True anaphylaxis to antivenin occurs rarely.
Serum sickness is common after antivenin but is usually self-
limiting & easily controlled with corticosteroids/histamines.
18. SCORPION STINGS: Management
Tachyarrhythmias can be treated with IV metoprolol or
esmolol.
Prazosin, an α-adrenoceptor antagonist, is indicated if
hypertension or pulmonary oedema develops.
Prazosin also stimulates the secretion of insulin (which often
falls during envenoming) & prevents hyperglycaemia.
Other treatments, as calcium or sympathomimetic drugs, are
of little value.
21. Single-choice Qs:
1. The most useful bed-side test to suggest snake bite
envenemoation is:
A. Prothrombin time.
B.20 minute whole blood clotting test.
C. INR.
D.Plateletes count.
E. PTT.
22. Single-choice Qs:
2. Management of snake bite includes all except:
A.Immobilize the bittenpart.
B. Apply a firm bandage.
C. Incision & sucking of the bittensite.
D. IV cannula on unaffected limb.
E.Reassure the ptient.
23. Single-choice Qs:
3.The following features occur in scorpion sting rather than snake
bites except:
A. Piloerrection.
B.hypoglycemia.
C.Hyperglycemia.
D. Hypertension.
E.siezures.