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Envenomation

Envenomation. Dr. George John, Division of Critical Care, Christian Medical College, Vellore. Common Problems. Snake Scorpion. Scorpion Sting. Autonomic Storm Myocardial Depression Central Nervous System dysfunction Endocrine Dysfunction. Management - 1.

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Envenomation

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  1. Envenomation Dr. George John, Division of Critical Care, Christian Medical College, Vellore

  2. Common Problems • Snake • Scorpion

  3. Scorpion Sting • Autonomic Storm • Myocardial Depression • Central Nervous System dysfunction • Endocrine Dysfunction

  4. Management - 1 • Analgesia: Pain relief for the local pain can be achieved with NSAID or local injection of 2% xylocaine (adrenaline free). Morphine (and other opioids) should be avoided as it can cause dysrhythmias. • Antiserum:In a study published in 2006, specific antiserum was found useful in the management of severe serious scorpion sting. Needs confirmation.

  5. Management - 2 • Prazosin: Prazosin is a competitive post synaptic alpha 1 receptor antagonist. It blunts the sympathetic storm and activates the venom inhibited calcium dependent potassium channels. Peak concentration is reached in 1-3hours and plasma half life is about 2-3hours. Clinically, it starts acting in 1 hour and maximum action occurs at the end of three hours. It is easy to administer even in rural settings. It is administered orally in a dose of 30ug / kg per dose for children and repeated every three hours initially and at six hour intervals later. However, because it is commonly available as a scored 1mg tablet and it is difficult to titrate the dose exactly on a weight basis, a dose of 250ug for children and 500ug for adults has been used initially and at 3hourly intervals with good results. Prazosin is stopped when the extremities become warm and dry. The number of doses of prazosin needed varies between 2 and 6 with a mean of 4.5 doses.

  6. Management - 3 • Lytic cocktail: This was the traditional therapy for scorpion sting. The “cocktail” consists of pethidine 100mg, chlorpromazine 50mg and promethazine 50mg in 50ml of 5% glucose. The dose is 0.3ml per kilogram body weight. The beneficial effect was probably due to the alpha blocking action of chlorpromazine. However, the opiate (pethidine) can potentially worsen cardiac arrhythmias. Its use has declined after after prazosin has been shown to be effective. • Glucose insulin potassium regimen: The dose of glucose is 0.5g/kg/hour and insulin is administered at a dose 0.3units / g of glucose. It can be prepared by adding 15units of plain insulin to 500ml of 10% glucose solution and infusing it at a rate of 5ml/kg/hour. Adequate potassium is to be added by monitoring serum potassium. However no controlled trials are available to document the benefit of this preparation.

  7. Management - 4 • Correct fluid loss • Correct acid base abnormalities. • Oxygen and respiratory support as indicated. • Diuretics can be used cautiously. • Inotropic support can be given : dopamine ( no evidence) or dobutamine 7 – 20 ug / kg / min (MAP < 60mm Hg, oliguria)

  8. Do not Use!! • Atropine • Morphine • Steroids • ACE inhibitors • Ca Channel blockers

  9. Snake Bite The venom is synthesized by the modified salivary glands and injected through special channeled or grooved teeth called fangs. In India, poisonous snakes belong to three broad families: 1. Elapidae: Cobras, Kraits 2. Viperidae: Vipers Russell’s viper, saw scaled viper Pit viper 3. Hydrophidae: Sea Snakes Poisonous snakes can be identified by their characteristic morphology.

  10. Local Effects This is related to the digestive function of the venom and causes local tissue necrosis. It is maximal with a viper bite and least with krait (so much so that the bite may go unnoticed and symptoms which follow may not be attributed to snake bite).

  11. Systemic Effects - 1 Neurotoxic On the basis of their mode of action they have been classified into two groups. The overall effect is to cause flaccid muscular paralysis, respiratory failure and death. The snakes causing this group of manifestations are:cobra, krait, sea snakes. • Group 1 – cobra neurotoxin, alpha-bungarotoxin. This causes an anti depolarizing, neuromuscular block of the motor end plate similar to d-tubocurarine. • Group 2 – krait neurotoxin, beta-bungarotoxin. This acts by producing a pre-synaptic neuromuscular block by decreasing the acetylcholine output from the motor nerve endings. Krait can cause fixed, dilated non reactive pupils simulating brain stem death – however, it can recover fully

  12. Systemic Effects - 2 Haemotoxic This is seen in viper envenomation. The haematological toxicity of the venom is due to the following: proteinases (coagulation / anticoagulation / fibrinolytic), phopholipases (haemolysis of red cells) haemorrhagins - non enzymatic polypeptides (affects the blood vessels causing vasoconstriction, vasodilatation and disruption of endothelial lining). A combination of these effects results in consumption of clotting factors, fibrinolysis, DIC and haemorrhage - both cutaneous and systemic (in the brain, lungs and kidneys). Shock can occur as a result.

  13. Systemic Effects - 3 Cardiotoxic Cardiotoxins affect the cell membranes directly. These cardiotoxins affect the skeletal, smooth and cardiac muscle causing cardiac depression, cardiogenic / vasogenic shock and systolic cardiac arrest. It is mainly seen in cobra bites. Shock can occur.

  14. Summary of Manifestations

  15. Management - Local • Tourniquet should be applied around a single boned part of the bitten limb between the wound and the heart. The pressure should be adequate to occlude lymphatics but not the distal arterial pulse. The tourniquet can be released briefly for a few seconds every 10minutes. Immobilise the affected limb. • Pressure immobilisation with partially overlapping spiral elastocrepe bandage can be done. • No compressive therapy if there is a lot of local necrosis as in a viper envenomation. 3. The local wound should be cleaned gently with normal saline. Short skin incisions and suction has been advised if the bite is less than 1 hour old.

  16. Management: Specific 1 • polyvalent antivenin is available in a lyophilized form (as liquid antivenin is unstable at room temperature). • active against the four common poisonous snakes in India – cobra, krait, Russel’s viper and saw scaled viper (Echis). average potency of the antiserum available is that 1 ml will neutralize 0.6mg cobra, 0.45mg krait, 0.6mg Russel’s viper and 0.45mg saw scaled viper venom • reconstitution involves the addition of 10ml of distilled water to an ampoule and shaking till the solution is clear. It should be administered intravenously as early as possible. It is essential to enquire about allergy (specially to horse serum). It is well to be prepared for an anaphylactic reaction during the antivenin administration.

  17. Management: Specific 2 • Standard High Dose: loading dose of 100ml followed by 50ml every 6 hours till the clotting time became normal. • Low Dose: The basis of low dose therapy is that the venom is absorbed only gradually into the systemic circulation and the low dose is sufficient to neutralize the absorbed quantity of venom. The low dose is given over a longer period as absorption of venom continues into the systemic circulation. • 20 ml over 1 hour followed by 10ml over 4 hours repeated till clotting is normal and then 10ml over 24 hours. • loading dose of 30 – 70 ml of antivenin followed by a 30 ml infusion over 6 hours, given every 6 hours and continued till the clotting time was normal when done twice, 6 hours apart. This is then followed by an infusion of 30ml over 24 hours. No change in dose for children as the amount of venom injected may be the same as in an adult.

  18. Management: Supportive 1 • Analgesicsfor pain • Antibioticsfor infection. The choice should cover for anaerobic infection. • Antitetanusprophylaxis • Replacement of coagulation factors / plateletsif there is active significant bleeding or bleeding into a vital organ.

  19. Management: Supportive 2 • Respiratory failure • Edrophonium / atropine 10mg / 0.6mg as a test • Neostigmine / atropine 0.5mg/0.6mg every 30 – 60 min • Mechanical ventilation • Shock Treat as appropriate • Renal Failure Dialysis

  20. References SNAKE: Banerjee et al. Neostigmine in the treatment of elapidae bite. J Assoc Physicians India. 1972; 20: 503 - 509 Thomas PP, Jacob J. randomized trial of antivenom in snake envenomation with prolonged clotting time. Brit Med J. 1985: 291: 177-178 Kakrani AL. rationale anti snake venom therapy: Randomized controlled trials or clinical judgement. J Assoc Physicians India. 1999: 47: 367 – 368 Tariang DD, Philip PJ et al. Randomized controlled trial on the effective dose of anti-snake venom in cases of snake bite with systemic envenomation. J Assoc Physicians India. 1999; 47: 369 – 371 Vijeth SR, Dutta TK et al. Dose and Frequency of anti-snake venom injection in the treatment of Echis carinatus (saw scaled viper) bite. J Assoc Physicians India. 2000; 48: 187-191 Srimannarayana et al. Randomised controlled trial on the effective dose of anti snake venom in case of snake bite with systemic envenomation. J Assoc Physicians India. 2000; 48: 458 – 459 Seth AK et al. Randomised controlled trial on the effective dose of anti snake venom in case of snake bite with systemic envenomation. J Assoc Physicians India. 2000; 48: 756 Srimannarayana J. et al. Rational use of anti snake venom (ASV): Trial of Various Regimens in Haematoxic Snake Envenomation. J. Assoc. Physicians India. 2004; 52:788 - 793

  21. References SCORPION:  Bawaskar HS, Bawaskar PH. Scorpion sting. J Assoc Physicians India. 1998; 46: 388 – 392 Kavathale, Khan A et al. Scorpion – Stings the limb and stuns the heart? J Assoc Physicians India 1999; 47: 1045 – 1046 Sundararaman T, Olithselvann M et al. Scorpion envenomation as a risk factor for development of dilated cardiomyopathy. J Assoc Physicians India 1999; 47: 1047 – 1050 Elatrous S et al. Dobutamine in severe scorpion envenomation. Effects on standard haemodynamics, right ventricular performance and tissue oxygenation. Chest 1999; 116: 748 – 753 Bawaskar HS, Bawaskar PH. Prazosin therapy and Scorpion envenomation. J Assoc Physicians India. 2000; 48: 1175 – 1180 Natu VS et al. Efficacy of Species Specific Anti-scorpion Venom Serum (AScVS) against severe serious scorpion stings ( Mesobuthus tamulus concanesis Pocock) – an experience from Rural Hospital in Western Maharashtra. J Assoc. Phys of India 2006; 54: 283 - 287

  22. THANK YOU!

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