Management of Snake BitesMabel Vasnaik

Dept of Emergency MedicineSt Johns Medical College Hospital

Overview

• Epidemiology• Antisnake venom (ASV) &

complications• Treatment of ASV

reactions• Other supportive

management

Incidence of Snakebite

• Globally 50 to 60,000 people die of snake bite each year• 90% from Asia and Africa

Kasturiratne A, Wickremasinghe AR et al. Estimating the global burden of snakebite: A

literature analysis and modelling based on regional estimates of envenoming and deaths.

PLoS Med 2008;5: e218. doi:10.1371/journal.pmed.0050218

Snakes of Medical Importance in South East Asia

• Viperidae

Russell’s viper (Daboia russelli)

Saw-scaled viper (Echis carinatus)

Hump nosed pit viper (Hypnale hypnale)

• Elapidae

Indian cobra (Naja naja)

Common krait (Bungarus caeruleus)

Etiology of Snake bite

• Common in rural areas

• Occupational hazard for farmers, fishermen, snake handlers.

• Snake accidentally trodden upon

• Picked up in a handful of crops.

• People who sleep on the floor at night

First AidDo it RIGHT

• Reassure patient. 70% nonvenomous

• Immobilise as in a fractured limb

• GH Get to a hospital as soon as possible

• Tell the doctor symptoms

of envenomation

Simpson ID. Snakebite Management in India, The First Few Hours: A Guide for Primary Care Physicians. J Indian Med Assoc 2007;105:324-335

Symptoms of Envenomation

• Neurological impairment

ptosis, muscle weakness, respiratory distress/arrest

• Hematological

bleeding from bite site, epistaxis, hemoptysis, hematuria, ecchymosis

• Painful Progressive Swelling

Feature Cobras Kraits Russells Viper

Saw Scaled Viper

Hump Nosed Viper

Local Pain/ Tissue Damage

YES NO YES YES YES

Ptosis/ Neurological Signs

YES YES YES! NO NO

Haemostatic abnormalities

NO NO! YES YES YES

Renal Complications NO NO YES NO YES

Response to Neostigmine YES NO? NO? NO NO

Response to ASV YES YES YES YES NO

Patient Assessment Phase: On arrival

• Airway, Breathing and Circulation

• Resuscitate as necessary

• Tetanus Toxoid

• Anti-biotic for cellulitis

or necrosis.

Diagnosis Phase: General Principles

• Identify the snake if possible

• Fang marks

• Look for features of envenomation

• Observation for 24 hrs

• Document time of

bite

Late-onset envenoming

• Krait and viper can take 6 to 12hrs

• Juvenile snakes, 8-10 inches long

Diagnosis Phase: Investigations20 Minute Whole Blood Clotting Test (20WBCT)

• Most reliable bedside coagulation test

• Clean dry glass vessel

• Leave few ml of blood undisturbed for 20 mins

Simpson ID. Snakebite Management in India, The First Few Hours: A Guidefor Primary Care Physicians. J Indian Med Assoc 2007;105:324-335

Other Investigations

• Hb/ PCV/ Platelet Count/ PT/ APTT/ FDP

D-Dimer

• Peripheral Smear

• Urine for Protein/ RBC/ Haemoglobinuria/ Myoglobinuria

• Serum Creat / Urea/ Potassium

Management

• Initial resuscitation

• Pain management

• Antisnake venom (ASV)

• Supportive treatment

• Treatment of complications

Pain management

• Paracetamol

• Opiates like Tramadol

• Avoid aspirin/NSAID’s

ANTI SNAKE VENOM

TOXIC COMPONENTS OF SNAKE VENOM

Protein components: 90-95%

Consist of Enzymes (Phospholipase A2,Proteolytic enzymes,Hyaluronidase)

Polypeptides – Pre-synaptic (Beta-bungarotoxin)

Post-synaptic (Alpha) neurotoxins (Bungarotoxin and cobrotoxins)

Non-protein components: 5-10%

Monovalent Vs polyvalent ASV

• Polyvalent is cheaper

• Very often snake is not identified

• ELISA kits not available

Anti Snake Venom (ASV)• Polyvalent, effective against • Russell's viper• Common Cobra • Common Krait • Saw Scaled viper • Ineffective against Humpnosed pit viper

ASV Preparation

• Liquid: 2yr shelf life, reliable cold chain, no reconstitution • Lyophilised: 5 yr shelf life, no cold chain, 30 – 60 mins to reconstitute

Should not be used indiscriminately

• Scarce, costly • Administer only with definite signs of

envenomation. • Unbound venom, neutralised when in bloodstream

or tissue fluid. • Risk of anaphylactic reactions

Simpson ID, Norris RL. The global snakebite crisis-A public health issue

misunderstood, not neglected. Wilderness and Environmental Medicine,

2009;20:43-56

ASV Dosage

• Russells Viper injects on average 63mg SD 7 mg of venom. Range 5mg – 147 mg.

• Each ASV vial neutralises 6mg of venom.• Initial dose should neutralise the average dose of

venom injected.(10 vials) • Total required dose between 10 to 25 vials

• Tun P, Khin Aung Cho. Amount of venom injected by Russell’s Viper (Vipera russelli) Toxicon 1986; 24(7): 730-733

ASV dosage

• Neurotoxic/ Anti Haemostatic 8-10 Vials

• ASV can be administered in two ways:• Slow IV (2ml/min). Each vial is 10ml • Infusion: ASV diluted in 5-10ml/kg NS/ 5D.• Administer over 1 hr at constant speed.• Closely monitor patient for 2 hrs.• Do not inject ASV locally at the site of bite.

Repeat Doses: Anti Haemostatic

• Initial 10 vials of ASV over 1 hr. • Repeat a CT 6hrs later. • If deranged give 2nd dose of ASV. • Repeat CT every 6 hrs and give ASV if indicated upto

a maximum of 25 vials.

Ghosh S, Maisnam I, Murmu BK, Mitra PK, Roy A, Simpson ID. A locally

developed snakebite management protocol significantly reduces overall anti

snake venom utilization in West Bengal, India. Wilderness Environ Med;

2008;19;267-74

Repeat Doses: Neurotoxic

• Give an initial dose of 10 vials.• If neurotoxicity persists after 2 hrs give 10 more vials. • If respiratory failure still persists continue ventilation. Evidence suggests that ‘reversibility’ of post synaptic

neurotoxic envenoming is only possible in the first few hours.

Srimanarayana J, Dutta TK, Sahai A, Badrinath S. Rational use of Anti snake venom (ASV): Trial of various Regimens in Hemotoxic Snake Envenomation. Journal of Assoc of Physicians India. 2004;52:788-793

Local envenoming

• Local swelling involving more than half of the bitten limb (in the absence of a tourniquet).

• Rapid extension of swelling • Development of an enlarged tender lymph node

draining the bitten limb.

Initial dosing exceptions

Vital life saving surgery• To resolve serious complications of snake bite• Intracranial bleed• Restore coagulation in shortest timeInitial dose 2-3 times the normal starting dose

ASV in pregnancy

Dosage is the same

Greatest risk in 1st trimester with coagulopathy

Spontaneous abortions can occur within 7 days

of the bite

Sebe A, Satar S, Acikalin A. Snakebite during pregnancy. Hum Exp Toxicol.

2005;24:341-5.

ASV in children• Snake injects the same amount of venom

whether it is a child or adult.

• Hence the dose of antivenom remains the same

Simpson, I.D., Norris, R.L, Snake antivenom product guidelines in India:

The devil is in the details. Wilderness Environ Med. 2007;18:163-168

Renal Failure and ASV

• Renal failure is a common complication of Russell's Viper and Hump-nosed Pit viper bites

• The contributory factors are intravascular haemolysis, DIC, direct nephrotoxicity, hypotension & rhabdomyolysis.

• Renal damage can develop very early in cases of Russell's Viper bite.

• ASV even if given 1-2 hours after the bite, is incapable of preventing ARF

Shastry JCM, Date A, Carman RH, John KV. Renal failure following snake

bite. Am J Trop Med Hyg 1977;26:1032-1038

Recovery Phase

• If an adequate dose of antivenom has been given systemic bleeding stops within 15-30 mins & coagulability is restored in 6 hrs.

• Post synaptic neurotoxic envenoming (Cobra) may begin to improve as early as 30 mins after antivenom.

• Presynaptic neurotoxic envenoming (Krait) usually takes a longer time.

• In hypotension, BP may increase after 30 mins

Recurrent Envenomation

• Once coagulopathy settles no further ASV should be administered, unless a proven recurrence of a coagulation abnormality is established.

• Prophylactic ASV not indicated to prevent recurrence

• Indian ASV is a F(ab)2 product and has a half-life of over 90 hours

Victims who arrive Late, after several days

• Document time of bite• Asymptomatic 24 hrs after bite.• Symptomatic 24 hrs after bite. • Venom can only be neutralised if it is unattached!

Antivenom Reactions• 20%of patients

• Early (within 10 to 180 mins)

• Late ( 5 days or more)

Pathophysiology

• Complement mediated anaphylactic reaction.

• Not IgE mediated

No role for test dose of ASV

• Skin/conjunctival sensitivity, tests IgE mediated type 1 hypersensitivity

• May delay treatment

• Can be sensitizing

ASV Reactions

ASV Reactions

• Urticaria, itching, fever, chills,• Nausea, vomiting, diarrhoea, abdominal cramps, • Tachycardia, hypotension, • Bronchospasm and angio-oedema

McLean-Tooke A P C, Bethune C A, Fay A C, Spickett G P. Adrenaline in the treatment of anaphylaxis: what is the evidence? BMJ. 2003; 327: 1332-1335

Treatment of ASV Reactions

• Adrenaline should be kept loaded before giving ASV • Stop the ASV temporarily• Give adrenaline at the first sign of a reaction • 0.5mg IM in adults• 0.01mg/kg IM in children• Repeat every 5 to 10 mins

Persistent hypotension, Life threatening anaphylaxis

• Adrenaline 0.2mg(200ug) of 1:10,000 dilution, IV bolus

• Repeat if necessary• If hypotension refractory to bolus dose start

an adrenaline infusion• Immediate Management of Airway &

Breathing

Epinephrine infusion

1mg epinephrine in 500ml of 5%D / NS

1-4ug/min (0.5 to 2ml/ min)

Titrate to effect

Treatment of Hypotension

Crystalloids NS bolus 1-2L

(10 to 20ml/kg in children)

SECOND- LINE THERAPY Corticosteroids

Hydrocortisone 200 – 500mg IV

(5-10mg/kg in children)

Methylprednisolone 125mg IV

(2mg/kg in children)

Prevents recurrent anaphylaxis

For allergic bronchospasm

Nebulization Salbutamol+ipratopium bromide

Nebulised adrenaline if required

Additional Treatment

• H1 antihistamine, 10mg chlorpheniramine maleate IV,

(0.2mg/kg children) or 22.5mg pheniramine maleate IV or 25mg promethazine HCl IV • H2 antihistamines, Ranitidine 50mg IV

Prophylaxis for ASV Reactions

Prophylaxis with hydrocortisone and chlorpheniramine bolus reduces incidence of

anaphylactic reactions

52 patients were randomised into 3 groupsGroup 1: 1000mg hydrocortisone in 300ml NS infusion 5 mins before and continued 30 mins after ASVGroup 2: Chlorpheniramine 10mg IV bolus was given 5min after ASV infusion was started in addition to the hydrocortisoneGroup 3: Placebo

Gawarammana IB, Kularatne M et al, Parallel infusion of hydrocortisone ± chlorpheniramine bolus injection to prevent acute adverse reactions antivenom for snakebites Med Journal of Australia. 2004;180(1):20-3.

Efficacy of subcut adrenaline in prevention of anaphylaxis

0.25 ml of subcut adrenaline vs placebo immediately before infusion of ASV in 101 patients and observed for anaphylactic reactions within 24 hrs.

The incidence of anaphylaxis was 11% in the study group and 43% in the control group, showing a statistically significant difference.

Premawardhena A, de Silva CE et al, Low dose subcutaneous adrenaline to prevent acute adverse reactions to antivenom serum in people bitten by snakes: randomised, placebo controlled trial BMJ. 1999; 318: 1041-1043

When to restart the ASV after a reaction

• Once the manifestations of the reaction have subsided

• Once the BP is under control• In severe reactions ASV can be restarted

under cover of an adrenaline infusion• Rate of ASV infusion can be decreased initially• Monitor the patient.

No absolute contraindications to antivenom

• Patients with previous reactions to antitetanus, antirabies serum

• Atopic diseases like severe asthma

• Give only with systemic envenomation

• Prophylactic regimes can be used

Repeat bite• Dosage and schedule of ASV remains

the same

• Higher risk of adverse reactions

• Prophylactic regimes can be used

Supportive management of snake bite victims

Neurotoxic envenomation

• Bulbar and respiratory paralysis.

• Aspiration, airway obstruction or respiratory failure.

• Intubate and mechanically ventilate.

Neurotoxic Envenomation-Role of Neostigmine

• An anticholinesterase like Neostigmine prolongs the life of acetylcholine and can reverse the respiratory failure and neurotoxic symptoms due to snake venom.

• Neostigmine TEST:

1.5-2.0 mg neostigmine with 0.6mg atropine IV Observe for 1 hr

Neostigmine particularly effective for post synaptic neurotoxins (Cobra).

• Improvement in ptosis, neck lift & single breath holding counts over 60 minutes

• 0.5mg neostigmine IV q 30 mins for 12 hrs Add 0.6mg atropine to 2.5mg neostigmine

• Neostigmine & atropine can be given as a continuous IV infusion in the above dosage for a period of 12 hours.

Haemostatic abnormalities:

• Strict bed rest to avoid even minor trauma

• Transfusion of FFP, cryoprecipitate, platelet concentrates, or even fresh whole blood can be life saving.

• Avoid intramuscular injections

Shock and myocardial damage:

• Correct hypovolemia with fluids

• CVP monitoring

• Inotropes if hypotension persists.

Renal failure

• Dialyze if necessary.

• Treat the Hyperkalemia

Bacterial infections:

• Infection at the site of the bite is common.

• Broad spectrum antibiotics

• Anti-tetanus toxoid

Surgical Intervention

• Debridement of necrotic tissue

• Fasciotomy for intracompartmental syndrome

Handling Tourniquets

• Sudden removal can lead to a massive surge of venom leading to neurological paralysis, hypotension.

• IV line, O2, to handle above complications

Nishioka SA. Is tourniquet use ineffective in the pre-hospital management

of South American rattlesnake bite? Toxicon 2000;38(2):151-2

Snake Venom Ophthalmia

• Cobras spit venom at the victim and can cause pain in the eyes and conjunctivitis.

• Immediately irrigate with large quantities of water

• Pain relief with 0.5% lignocaine eye drops.

• Topical antimicrobials

Prevention of Snake Bite

Prevention of Snake bites

1. Education

2. Protection of human dwelling places

3. Precautions to be taken while working in the fields

4. Prompt treatment

To Summarize

• Problem of immense magnitude

• Diagnosis of envenomation

• Resuscitation

• Antisnake venom

• ASV Reactions