Snake Poisoning

SNAKE POISONING:

Ophitoxemia  refers  to  snake  poisoning.

Most of the snakes are non-poisonous. Difference between poisonous n non-poisonous snakes is:

Clinical features: There are six families of snake;

(A) Neurotoxic: (elapids, i.e.  cobra, krait, coral  snakes)

• Krait is  the  most  common  poisonous  snake  in  india and its lethal dose is 6mg.
• These have  minimal  reaction  locally,  but produce  strong  neurotoxicity.  They act  on  motor  nerve  cells,  resembling  poisoning  with  curare.  There is  weakness  of  legs  and  face.
• Muscle paralysis  occurs  in  following order  :-  mouth (first)  followed  by  throat  and  finally  respiratory  muscles.
• Cobra  venom also  produces  convulsions (krait  venom  produces  only  paralysis).

(B) Vasculotoxic  (hematotoxic)

• It  includes  vipers:  which   contains  hemolysins  and thromboplasin  which  cause  widspread
• endothelial  damage  and hemolysis.
• Locally  at  the  site  of bite,  there  is  severe  oozing of  blood.
• There may be  coagulation  abnormalities  with  death  due to  hemorrhagic  shock .
•  Hematuria  and hemoglobinuria  occurs due  to  hemolysis. 

(C) Myotoxic  (musculotoxic)

• These  are sea  snakes. Their  venom  produces  generalized  muscle  pain, weakness,  followed  by
• polymyositis,  myoglobinuria,  hyperkalemia,  rhabdomyolysis. and increased  muscle  enzymes.  Finally  there is  respiratory  and renal  failure.

Treatment for  snake bite

• Reassurance  should  be given to  patient.
• Application  of  pressure over bitten  area which  delays  absorption  of venom.
• Tie a  broad  firm  bandage  (tourniquet)  proximal  to  the  bitten  area and around  the  limb  which  would occlude venous and lymphatic  drainage  but  not  arterial  or  deep venous  flow.
• Limb immobilization.
• Local  incision  and suction should  not  be done as  it  can cause  local  injury  and nerve  damage.
• Clean  the  wound  with  soap  and water  or iodine  and  cover  with  sterile  dressing.
• Polyalent  snake  antivenom (PAV) is  given.  However  it  is  given  only  in  following situations :

1. Rapidly  progressive  and  severe local  findings.
2. There are manifestations  of systemic  toxicity.

• Polyvalent snake  antivenin  (PAV is  prepared  by  hyperimmunizing  horse  against  the  4  common
• Poisonous snakes  i.e.  cobra  (naja naja),  common  krait  (Bungarus  caerulus),  russel’s viper  (Daboia  russel)  and Saw scald viper (Echis  carinata). It  is  prepared  in  king  institute  (chennai),  haffkine  institute  (mumbai),  serum  institute (pune)  and kasauli.
• Polyvalent antisnake  venom  is  useful when  given within four  hours  of snake  bite.  It  is  of  less  value if  delayed  for  eight hours  and is  of doubtful  value  after  24 hours.  Each  vial  of  polyvalent  antisnake  venom  neutralize about  6-8  mg of venom.

Initial  dose depends  upon  symptoms  :

1. Minimal  (local  swelling,  no systemic  sytnptoffis)  > 5  vials.
2. Moderate  (swelling  progressing  beyond  site of bite with systemic  reaction)  – 10  vials.
3. Severe  (marked  local  reaction,  severe  systemic  symptoms)  → 10-15  vials.

•  In  neurotoxic  poisoning,  a  second dose  of 10 vials  should  be  given  after  I  hour.

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