SNAKE BITE

SNAKE BITE - Facts It is a major medical concern. In India, every one minute one person is bitten by a snake. Every two hours one person dies. In India, over four lakhs persons bitten by snakes every year. Envenomation in 82,000. Death occurs in 11,000.

SNAKE BITE – Facts contd… Many death occurs before the victim reaches the hospital. Most of the victims are young and the only bread winner.

SNAKE BITE – Facts contd… All snakebite patients do not develop clinical symptoms and signs of envenomation reactions because snakes sometimes bite without injecting venom or inject too little venom to cause damage. Site of action of venom varies from one snake to another. Complications due to snake bite may also vary from individual to individual. The status of poisoning cannot be judged by the bite mark reaction to envenomation, size or the type of snake. However, one has to observe for signs and symptoms which may develop within 24 to 48 hours.

What are the types of snakes? Snakes are classified into three types for all practical purposes and they are Cobra group [Colubridae] b) Viper group [Viperidae] c) Sea snake group [Hydrophidae]

Manifestations & Response to Drugs Item Cobra Kraits Russells Viper Saw Scaled Viper Hump Nosed Viper Local Pain/ Tissue Damage YES NO Ptosis/ Neurological Signs YES! Haemostatic abnormalities NO! Renal Problems Response to Neostigmine NO? Response to ASV

CLINICAL ASPECTS OF SNAKE BITE Pathophysiology of snake venom: Snake venom is mostly water in nature. It consists of numerous enzymes, proteins, aminoacids, etc., Some of the enzymes are proteases, collagenases, arginine ester hydrolase, hyaluronidase, phospholipidase, metallo-proteinases, endogenases, autocoids, thrombogenic enzymes, etc., These enzymes also act like toxins at different tissues of the body, and are grouped under neurotoxins, nephrotoxins, hemotoxins, cardiotoxins, cytotoxins etc., resulting in organ dysfunction / destruction.

Symptoms and Signs General symptoms and signs of Viperine envenomation Swelling and local pain with or without erythema or discoloration at the site of bite Tender enlargement of local lymph nodes as large molecular weight Viper venom molecules enter the system via the lymphatics. Bleeding from the gingival sulci and other orifices. Epistaxis. The skin and mucous membranes may show evidence of petechiae, purpura ecchymoses. The passing of reddish or dark-brown urine or declining or no urine output.

Symptoms and Signs contd… General symptoms and signs of Viperine envenomation Lateralising neurological symptoms and asymmetrical pupils may be indicative of intra-cranial bleeding. Vomiting Acute abdominal tenderness which may suggest gastro-intestinal or retro peritoneal bleeding. Hypotension resulting from hypovolaemia or direct vasodilation. Low back pain, indicative of an early renal failure or retroperitoneal bleeding Muscle pain indicating rhabdomyolysis. Parotid swelling, conjunctival oedema, sub-conjunctival haemorrhage

Symptoms and Signs contd… General symptoms and signs of Elapid envenomation: Swelling and local pain with or without erythema or discoloration at the site of bite (Cobra). Local necrosis and/or blistering / bullae(Cobra). Descending paralysis, initially of muscles innervated by the cranial nerves, commencing with ptosis, diplopia, or ophthalmoplegia. The patient complains of difficulty in focusing and the eyelids feel heavy. There may be some involvement of the senses of taste and smell. Problems of vision, breathing and speaking Paralysis of jaw and tongue may lead to upper airway obstruction and aspiration of pooled secretions because of the patient’s inability to swallow.

Symptoms and Signs contd… General symptoms and signs of Elapid envenomation Numbness around the lips and mouth, progressing to pooling of secretions, bulbar paralysis and respiratory failure. Hypoxia due to inadequate ventilation can cause cyanosis, altered sensoriun and coma. This is a life threatening situation and needs urgent intervention. Paradoxical respiration, as a result of the intercostal muscles becoming paralysed is a frequent sign. Stomach pain which may suggest submucosal haemorrhages in the stomach (Krait). Krait bites often present in the early morning with paralysis that can be mistaken for a stroke. Eye pain and damage due to ejection of venom in to the eyes by spitting cobra(as observed in Africa)

Symptoms and Signs - summary Drooping eyelids Double vision Difficulty in swallowing Difficulty in speaking Difficulty in breathing Bleeding from the gums Unusual bruising Rapid swelling, note the extent every 10 minutes with a pen Late onset envenomation and overlapping.

Approach to Management

Discarded methods Tourniquets Cutting and Suction Washing the wound Electrical Therapy Cautery Cryotherapy Pressure immobilization method

Tourniquets The use of tight tourniquets made of rope, string and cloth have been traditionally used to stop venom flow into the body following snakebite. However, they have the following drawbacks and problems: Risk of ischemia and loss of the limb Risk of necrosis Risk of massive neurotoxic blockade Risk of embolism if used in Viper bites. Release of tourniquet may lead to hypotension. Give patients a sense of false security, which encourages them to delay their journey to hospital

Cutting and Suction Cutting the site of bite and suctioning of incoagulable blood increases the risk of bleeding to death as well as increases the risk of infection. No venom is removed by this method

Washing the Wound Victims and bystanders have a tendency to wash the wound to remove any venom on the surface. This should not be done as the action of washing increases the flow of venom into the system by stimulating the lymphatic system

Electrical Therapy Electric shock therapy for snakebite received a significant amount of press in the 1980’s. The theory behind it stated that applying an electric current to the wound denatures the venom . Much of the support for this method came from letters to journals and not scientific papers. It has been demonstrated that the electric shock has no beneficial effect and hence, it has been abandoned as a method of first aid.

Cautery treatment Cautery treatment is followed in some areas which is injurious and not beneficial

Cryotherapy Cryotherapy involving the application of ice to the bite was proposed in the 1950’. It was subsequently shown that this method had no benefit and merely increased the necrotic effect of the venom.

Pressure Immobilisation Method (PIM) PIM was developed in Australia in 1974 by Sutherland and gained some supporters on television and in the herpetology literature. Some medical textbooks have referred to it. Further work done by Howarth demonstrated that the pressure, to be effective, was different in the lower and upper limbs. The upper limb pressure was 40-70mm of Mercury; the lower limb was 55- 70mm of mercury. Work carried out by Norris showed that only 5% of lay people and 13% of doctors were able to correctly apply the technique! In addition, pressure bandages should not be used where there is a risk of local necrosis, that is in 4/5 of the medically significant snakes of India. In view of the difficulties encountered at every level, Pressure Immobilisation method can not be recommended for use at present.

Management - Investigations 20 Minute Whole Blood Clotting Test (20WBCT) REQUIREMENTS: Clean and dry glass test tube. 2ml disposable syringe Cotton Antiseptic Solution Clean gloves one pair. (The test tube must not have been washed with detergent, as this will inhibit the clotting mechanism)

Management - Investigations 20 Minute Whole Blood Clotting Test (20WBCT) - Procedure The most reliable test of coagulation and can be carried out, at the bedside without specialist training. Wash hands with soap and water and wear the gloves. Collect 2ml blood from peripheral vein of the unaffected limb. 2 ml of fresh venous blood is placed in a clean and dry glass test tube and left untouched and unshaken at ambient temperature for 20 minutes. Note the time. The test tube is gently tapped and if the blood is still liquid then the patient has incoagulable blood. The test tube must not have been washed with detergent, as this will inhibit the contact element of the clotting mechanism.

20 Minute Whole Blood Clotting Test (20WBCT)

Management - Investigations Other useful tests: Clinical Test – PR / BP / RR / Postural Blood Pressure Lab Studies – Hb / PCV / PL-Count / PT / APTT / FDP / D-Dimer / Peripheral Smear / Blood grouping / Rh typing / Urine tests for Proteinuria / RBC / Haemoglobinuria / Myoglobinuria / Bio chemistry for serum creatinine / Urea / Electrolytes / Oxygen saturation. Imaging studies – X-ray Chest / CT / Ultrasound (whenever required) 4. Others – ECG and other special investigations when needed.

Management - Treatment Currently recommended First Aid: The first aid being currently recommended is based around the pneumonic “Do it R.I.G.H.T. It consists of the following: R. = Reassure the patient. 70% of all snakebites are from non- venomous species. Only 50% of bites by venomous species actually envenomate the patient I = Immobilize without compression. No tight bandages or ties. G. H. = Get to Hospital fast. Traditional remedies have NO PROVEN benefit in treating snakebite. T= Tell the doctor of any systemic symptoms such as ptosis that manifest on the way to hospital.

ANTI-SNAKE VENOM

Points to be remembered before using Anti Snake Venom ( ASV) No alternative to Anti Snake Venom ASV available in our hospitals is polyvalent anti venom There is no dose adjustment for ASV administration for children Anaphylactic or late serum sickness cannot be detected or prevented by test dose Health staff administering the ASV should read the manufacturers information leaflet ASV can be administered as IV infusion in Normal Saline or Glucose. It should not be given as IV bolus or IM directly ASV is administered slowly over a period of one hour

Points to be remembered before using Anti Snake Venom ( ASV) contd… ASV is required only to those who show definite signs and symptoms of envenomation There is no prophylactic dose of ASV ASV is a biological drug, hence anticipate reaction ASV neutralizes the unbound venom, hence give it early ASV administration should not be delayed or denied on the grounds of anaphylactic reactions to a deserving case Total dose requirement cannot be decided on the basis of Whole blood clot test (or) clinical signs and symptoms Even if the patient develops reaction the total dose required should be administered slowly after the patient recovers from the reaction.

Points to be remembered before using Anti Snake Venom ( ASV) contd… There is no other drug of choice other than ASV for the treatment of snake poisoning There is no prophylactic dose for ASV The patient has to be closely monitored atleast for 2 hours No interaction with Inj.ASV has been reported Fetal risk due to Inj. ASV has not been established or studied in humans Safety status for use of Inj.ASV during pregnancy has not been established. Timely administration of Inj.ASV will not gurantee the recovery or protect the individual from the venom induced toxicity or complications definitely.

ASV Administration: Dosage Risk and Wastage ( Ian D.Simpson Model ) Low wastage High wastage High risk Inj.ASV -Not available - Insufficient administration Inj.ASV – Too little supply Species are different Low risk Effective dose of Inj.ASV to envenomed patients Receive Inj.ASV when not required Too much Inj.ASV Unnecessary Inj. ASV

Recommended Dose of ASV Haemotoxic Envenomation: Treat the patient with Anti Snake Venom(ASV) Start IV Normal Saline with wide bore needle Begin with one Vial of ASV in one pint of NS and start 10-15 drops per minute for 15 minutes & watch for reactions. If the patient is not having signs and symptoms of anaphylactic shock continue the ASV drip with remaining seven vials/ampoules Continue to monitor the vital signs at five minutes interval for first 30 minutes and then at 15 minutes interval for two hours

Recommended Dose of ASV Neurotoxic Envenomation: Treat the patient with Antisnake venom (ASV) with the same dose for Haemotoxic Envenomation  plus Inj.Neostigmine 1.5 mg (Test dose) as I.M and Inj.Atropine 0.6 mg(Test dose) as I.V After that observe patients for every five minutes for 30 minutes for signs of response

Repeat Dose For Haemotoxic Envenomation: 5 vials after 6 hours (if the toxicity persists) For Neurotoxic Envenomation: 5 vials after 2 hours (if the toxicity persists) Most of the victims do not require more than 18 to 20 vials.

ASV in special situations Victims requiring life saving surgery. Victims who arrive late Repeat snake bites Snake bite in pregnancy and lactating women Victims having other comorbid conditions – Autoimmune disorders, debilitating status, endocrine disorders, immuno supressed status, HIV AIDS, cancer, asthma and allergy disorders, etc.,

ASV Reactions itching (often over the scalp) urticaria, even a single spot nausea, vomiting, abdominal colic, diarrhoea tachycardia fall in blood pressure, low volume pulse dry cough bronchospasm / Rhonchi / Stridor (rarely) angio-oedema of lips and mucous membrane. fever / shaking chills (rigors) febrile convulsions in children sweating / cold and clammy skin / central cyanosis

Management of Allergic Reactions If signs and symptoms of anaphylactic shock develop, Stop the ASV drip temporarily and treat the shock with: Inj Hydrocortisone 100 mg IV or Inj Dexamethasone 8 mg IV Inj.Phenaramine maleate 2ml IV Inj,Adrenaline 1:1000 (0.5 ml)IM Inj .Deriphyline 2ml IV Oxygen administration IV.Normal saline as life line As soon as the patient recovers or If the patient is not having signs and symptoms of anaphylactic shock continue the ASV drip with remaining seven vials/ampoules slowly. Continue to monitor the vital signs at five minutes interval for first 30 minutes and then at 15 minutes interval for two hours Stabilise the patient and refer to the higher institution – if needed

Surgical Issues The surgical issues observed in snake bite cases are Ulcer following snakebite Necrosis of the skin and underlying tissues Gangrene of the toes and fingers Debridement of necrotic tissues Compartment syndrome and others

Surgical Issues Assessment: * Assess for internal and external surgical issues related to envenomation carefully and observe for the same while the victim is at hospital and / or during follow up care. * Wound status * Use of topical agents / traditional medicine * Compartment syndrome - Less common - Consider compartment syndrome if any of the following 6 Ps. or a combination of them appear. Pain on passive stretching Pain out of proportion Pulselessness Pallor Parasthesia Paralysis The limb can be raised in the initial stages to see if swelling is reduced. However, this is controversial as there is no trial evidence to support its effectiveness.

Surgical Issues Action Required: * Care of the wound - Apply appropriate topical agents and dressing - Maintain proper wound enviroment - Do surgical debridement, if needed refer to surgeon * Prepare and proceed to skin grafting later (if required) * Measure intra compartmental pressure (ICP) in suspected cases by Intra compartmental monitoring machine(Stryker pressure monitor) or by use of a saline monitor * Monitor ICP every 30 to 120 minutes if required * Proceed with fasciotomy if the ICP exceeds greater than 30 to 40 mm of Hg. * Restore coagulation time before commencing the procedures.

Points to be remembered Fasciotomy does not remove or reduce any envenomation. Visual impression is an unrealistic guide to estimate the ICP. Tissue injury after compartment syndrome.may be disproportionate to the clinical status Fasciotomy is not required for every case.

Referral Aspects Who needs: Patient requiring Respiratory support Surgical intervention-Necrosis / Fasciotomy Spontaneous persistent bleeding Co-morbid diseases Acute impending kidney failure

Referral Aspects When: Refer the patient after stabilizing the case and after giving injection ASV – 1st dose

Referral Aspects Where: Refer to higher institution having Ventilator Dialysis facilities Measures to provide further supportive treatment.

Instructions while referring Inform the need for referral to the patient and/ care giver [ family member or the accompanying attendant ] Give prior intimation to the receiving center using available communication facilities Arrange for an ambulance Transfer in a vehicle to Secondary Care Hospital or Tertiary Care hospital. where mechanical ventilator and dialysis facilities are available Continue life supporting measures Provide airway support with the help of an accompanying staff Send the referral note with details of treatment given Instruct one staff to accompany the patient during transportation if required. Hand over the referral slip with details regarding treatment given Mention the clinical status clearly in the referralat the time of referral.

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