Snake Poisoning

Classification of Snake

A. Non poisonous e.g. rat snake, vine snake, and mud snake.

B. Poisonous

1. Viperidae

Russell's viper

Gaboon viper

Saw scaled viper

2. Crotalidae

Rattlesnakes

Pigmy rattlesnakes

Pit viper

Copperheads

Cottonmouths (water moccasins)

Bushmaster

3. Elapidae

Cobras

Kraits

Mambas

Tiger snake

Taipan

Coral snakes

4. Hydrophidae or sea snakes

All sea snakes are poisonous but they seldom(rarely) bite.

5. Colubridae

Boomslangs

Bird snake of the African continent.

6. Atractaspididae

Burrowing asps

Burrowing or mole vipers/false vipers

 

COMMON POISONOUS SNAKES:

      1. Common Cobra
      2. The King Cobra
      3. Common Krait
      4. Banded Krait
      5. Russell’s Viper
      6. Saw-Scaled Viper

Poison Apparatus (Modified salivary gland)

Gland

Duct

Fangs

Poison Glands:

They are the salivary glands of the snake and are situated behind the eyes, one on each side of the head above the upper jaw.

FANGS:

All the poisonous snakes have two fangs. These are curved teeth situated on the maxillary bones and lie along the jaws, and are covered by a flap of mucous membrane.

They are bigger than the other teeth and are grooved or canalized in poisonous snakes, and are solid in non-poisonous snakes.

SNAKE VENOM:

Venom is the saliva of the snake.

Cobra venom is faint transparent yellow and is slightly viscous. When exposed to sun, it becomes slightly turbid. Russell's viper venom is white or yellow.

Venom is secreted by special glands near the upper jaw of the snakes which are akin to human parotid glands. During the process of bite, the glands are pressed and the venom is squeezed and channelled through the grooves or channels of the fangs.

Composition of Snake Venom

It is basically a mixture of toxalbumins and enzymes in varying proportions. The enzymatic components cause local and systemic effects and the non-enzymatic compounds provide lethality .

Toxalbumin

Neurotoxins

Cardiotoxin

Myotoxin

Hemolysin

Fibrinolysin

Enzymes

Cholinesterase

Hyaluronidase

Proteolytic enzymes (Protease)

Phospholipase A,B,C,D

Lecithinases

Ribonuclease

Deoxyribonuclease

The colubrine and elapidae venom is mainly neurotoxic, and has a primary toxicity for the respiratory and cardiac centers.

The viperine venom is mainly hemotoxic and causes intravascular hemolysis and depression of the coagulation mechanism.

The sea snake venom is myotoxic.

Ophitoxaemia is poisoning by snake venom.

Signs and Symptoms:

The most common symptom following snake bite (poisonous or non-poisonous) is fright, especially the fear of rapid and unpleasant death.

Due to fright, the victim may become semiconscious with cold clammy skin, hypotension, feeble pulse and rapid breathing. These emotional symptoms appear within few minutes of the bite. Sometimes, it produces psychological shock and even death. It may also give rise to tetanus or gas gangrene.

Local signs and symptoms: (Ref Internet)

Fang marks,

Pain

Swelling

Edema & erythema

Lymph node enlargement, blistering

 

Systemic (Ref Internet)

      • Nausea and vomiting
      • Diarrhea
      • Paresthesias
      • Cranial nerve palsies
      • Flaccid muscles (including respiratory muscle paralysis)
      • Hypotension & shock
      • Oliguria

 

Indications for antivenom administration 
Systemic envenoming 
Hemostatic abnormalities: Spontaneous systemic bleeding, 
coagulopathy or thrombocytopenia 
CNS: Ptosis, external ophthalmoplegia, paralysis 
CVS: Hypotension, shock, cardiac arrhythmia, abnormal ECG 
Acute renal failure: Oliguria/anuria, elevated creatinine/urea 
Hemoglobin/myoglobinuria, other evidence of intravascular 
hemolysis or generalized rhabdomyolysis 
Local envenoming 
Local swelling involving more than half of the bitten limb (in 
the absence of a tourniquet) 
Swelling after bites on the digits (toes, and especially fingers) 
Rapid extension of swelling 
Enlarged tender lymph node draining the bitten limb.

Difference between poisonous and non-poisonous snakes

Trait

Poisonous snake

Non-poisonous snake

Head scales

Small (in vipers)

Large (in others)

Usually large

Belly scales

Large and cover entire breadth.

Small or moderately large, but do not cover the entire breadth.

Fangs

Hollow like hypodermic needles

Short and solid

Teeth

Two long fangs

Several small teeth

Tail

Compressed

Not much compressed

Habits

Usually nocturnal

Not so

Difference between cobra and viper

Trait

Cobra

Viper

Head

Usually small, covered by large scales or shields of special forms.

Large; broader than body and covered by numerous small scales

Body

Long and cylindrical

Short

Narrow neck

Pupil

Round

Vertical

Maxillary bone

Carries poison fangs and other teeth

Carries only poison fangs

Fangs

Grooved, short, fine

Canalized, long

Venom

Neurotoxic

Hemotoxic

Tail

Round

Tapering

Eggs

Lay eggs

Give birth to young ones

Polyvalent Anti-snake Venom (PAV) is prepared by hyper-immunizing horses against the venom of the four common poisonous snakes, i.e., cobra, common krait, Russell's viper and saw-scaled viper. Plasma obtained from the hyperimmunized horses is concentrated and purified.

It is useful when given within four hours of bite. It is of less value if delayed for eight hours, and is of doubtful value after twenty-four hours. Each vial of PAV will neutralize about 6 to 8 mg of venom.

20 minutes blood clotting test :

Few ml. of fresh venous blood is put in a clean dry glass tube and left undisturbed for 20 minutes and then gently tilted. If the blood is still liquid, it indicates viper bite. This test is repeated every 6 hours for determining repeat dose requirement. Normalization of clotting time is taken as endpoint of therapy. After that the test is done at 12 hour intervals for at least 48 hours to detect recurring envenoming. Repeat dosing is required for recurrence of systemic signs.

 

First Aid in case of Snake Bite:

1) Assure the patient.

2) Apply firm pressure over the bitten area, which delays absorption of venom.

3) Pressure immobilization is recommended  for elapid and sea-snake bites, but not for viper bites as it may cause local necrosis.

Immediately apply a broad firm bandage on the bitten area and around the limb. As much of the limb should be bandaged as is possible. It should be tight enough to occlude the superficial venous and lymphatic return, but not the arterial or deep venous flow.

4) Immobilize the limb, as movement can accelerate the spread of venom. Avoid elevation of an extremity, as it may hasten systemic absorption of venom.

5) Local incision and suction should not be done as it can cause local bleeding and nerve injury.

6) Do not suck venom out of the wound, and do not use chemicals or medicines on the wound.

7) Clean the wound with soap and water, or iodine and cover with a sterile dressing.

8) Make patient lie on one side in the recovery position so that the airway is clear, in case of vomiting or fainting.

Management & Treatment

A. Recommend first aid method

      1. Assurance the victim
      2. Immediately apply a broad firm bandage (Compression bandage) on bitten area.

B. Quick Hospitalization

      1. Rapid clinical assessment & resuscitation (by ABCD): Airway, Breathing, Circulation, Dehydration
      2. Detailed History & Clinical assessment

Circumstances of bite

Site, Time of bite

Progressive symptoms & signs (Local, Neurogenic, Hematological)

Description of the bitten snake

C. Specific Treatment (Reddy)

1. Anti-venom Treatment

Polyvalent Antisnake Venom

2. Antibiotics

Inject tetanus antitoxin or a booster dose of tetanus toxoid.

A broad spectrum antibiotic should be given if there is severe tissue involvement.

3. If there are signs of neuroparalysis, give neostigmine with atropine i.v. to counteract the muscarinic effects

4. In viper poisons, sedatives may be given to relieve pain and nervousness.

5.  Ventilator care

Mechanical ventilatory support is necessary in respiratory failure.

6. Hypotension & Shock

In severe poisoning, infusion of normal saline or transfusion of blood or plasma are very useful.

7. Hemostatic disturbances

Heparin may be given i.v. if there are clotting abnormalities.

8. Oliguria and renal failure

Rehydration, Diuretic or dopamine

Hemodialysis may be necessary. Peritoneal dialysis

Complications: (Ref Internet)

Compartment syndrome (Pressure within compartment restricting the blood flow)

Tissue necrosis

Coagulopathy (impaired clot formation) and spontaneous bleeding

Paralysis & coma

Hypotension & shock

Respiratory Failure

Renal Failure

Indications for antivenom administration 
Systemic envenoming 
Hemostatic abnormalities: Spontaneous systemic bleeding, 
coagulopathy or thrombocytopenia 
CNS: Ptosis, external ophthalmoplegia, paralysis 
CVS: Hypotension, shock, cardiac arrhythmia, abnormal ECG 
Acute renal failure: Oliguria/anuria, elevated creatinine/urea 
Hemoglobin/myoglobinuria, other evidence of intravascular 
hemolysis or generalized rhabdomyolysis 
Local envenoming 
Local swelling involving more than half of the bitten limb (in 
the absence of a tourniquet) 
Swelling after bites on the digits (toes, and especially fingers) 
Rapid extension of swelling 
Enlarged tender lymph node draining the bitten limb.

 

Table 46.2: Assessment of severity of envenomation 
Category 
No envenomation 
Mild envenomation 
Moderate envenomation 
Findings 
Absence of local or systemic reactions, 
fang marks +/-. 
Fang marks, moderate pain, minimal 
local edema (0—15 cm), erythema +, 
ecchymosis +/-, no systemic reactions. 
Fang marks +, severe pain, moderate 
local edema (15—30 cm), erythema 
+, ecchymosis +, systemic weakness, 
sweating, syncope, nausea, vomiting, or 
thrombocytopenia and anemia. 
Fang marks +, severe pain, severe 
local edema ( > 30 cm), erythema +, 
ecchymosis +, hypotension, parasthesia, 
coma and respirator failure. 
Severe envenomation 
Flow chart 46.1: 
'Dry bite' or minimal 
envenomation 
Observe for 8—12 h 
No progression 
of symptoms 
Antivenom 
not required 
Management of snake bite poisoning 
Snake bite 
Moderate to severe 
envenomation 
Local edema 
and ecchymosis 
Immobilization 
Initial dose of 
antivenom 
Dialysis 
Local redness and 
neuroparalysis 
Pressure immobilization 
Initial dose of antivenom 
Ventilator 
Atropine and neostigmine 
Blood transfusion 
Envenomation progression 
No 
No further 
treatment needed 
Yes 
Repeat dose of 
antivenom

Absorption and Excretion:

Snake venom is poisonous only when injected, and is harmless when taken by the mouth, as it will be digested by enzymes in intestinal tract and absorbed as amino acids. It is excreted by kidneys, milk and probably by salivary glands and the mucous membranes.

The Circumstances of Poisoning:

(1) Poisoning is as a rule accidental.

(2) Occasionally, a murder is committed by throwing a poisonous snake on the bed of sleeping person.

(3) It is very rarely used for suicide.

(4) Cattle are sometimes poisoned by snake venom.

Postmortem Appearances:

Poisonous snakes leave two or occasionally one fang mark. Non- poisonous snakes leave a semicircular set of tooth- marks.

Bite site might be swollen, redness, hemolyzed blood stain

Washing from the bite area may contain cholinesterase or thromboplastin.

Kidneys are inflamed and show marked congestion.

Acute renal failure is the leading cause of death in viper bite.

Hemorrhages into the bowel, purpuric spots on pericardium, and hemorrhages in the lungs and in many tissues may be seen.

Internal organs are congested.