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MANAGEMENT OF SNAKEBITES IN SRI LANKA

 
 

Dr. ARIARANEE GNANATHASAN
Dept Of Clinical Medicine
Faculty Of Medicine
Colombo
SRI LANKA

 

Introduction

Snakebites are a common hazard in Sri Lanka , especially in rural areas. The morbidity and mortality of snakebites add significantly to the health care cost of the country. The venomous snakes found in Sri Lanka include;

  1. Cobra (Naja naja)
  2. Common Krait (Bungarus caeruleus)
  3. Ceylon Krait (Bungarus ceylonicus)
  4. Russell’s viper (Duboia russelli)
  5. Saw scaled viper (Echis carinatus)
  6. Sea snakes (Pelamis sp., Hydrophis sp.)
  7. Hump nosed viper (Hypnale hypnale)
  8. Green pit viper (Trimeresures trigonocephalus)

The first six snakes are considered to be highly venomous and the latter one is moderately venomous. Since recently, the morbidity and mortality of hump nosed viper bites is more appreciated, especially with regard to acute renal failure following bites. Its role as a moderately venomous snake is reconsidered.

Management of snakebites

The approach in management of snakebites can be summarized as follows;

  • First aid treatment
  • Transport to hospital
  • Rapid clinical assessment and resuscitation
  • Detailed clinical assessment and species diagnosis
  • Investigations/ laboratory tests
  • Antivenom treatment
  • Supportive / ancillary treatment
  • Rehabilitation
  • Treatment of chronic complication

First aid

The recommended first aid treatment for any snakebite includes, reassurance, removal all rings, bracelets from the bitten part of the body, washing the bitten area with soap & water, Keeping the stricken limb below the level of heart and Immobilizing the bitten limb with a splint or a sling.

Medical help should be sought as soon as possible.

Things that are not recommended to do in event of a snakebite include; making cuts or incisions at bite site, ‘sucking out’ venom from wound, applying ice packs to bitten area, use of conventional tourniquet, taking alcohol, herbal medicine or Aspirin for pain relief

Transport to hospital

Transport to hospital should be safe and quick as possible. Any mode of transport such as bicycle, cart, motor vehicle, train or boat should be used or patient should be carried. However it is important to reduce any movement of the victim while transporting to avoid systemic absorption of the venom.

Emergency unit care

A critically ill patient can present to the emergency care unit of the hospital with any of the following complications of snakebite.

  • Respiratory arrest
  • Cardio-respiratory arrest
  • Death on admission
  • Coagulopathy
  • Hypotension & shock
  • Renal failure

In such situations, immediate resuscitation with attention to airway, breathing and circulation (A,B,C) is carried out in line with emergency life support guidelines. This may include, clearing and maintaining airway, Ambu bag and mask ventilation or ventilation with intubation, establishing IV access and correcting any circulatory deficit.

Detailed clinical assessment and identification of snake

The next step is detailed clinical assessment of the patient. The most important aim in this step is to identify the snake. Correct clinical identification of the snake is important because; features of envenomation vary from species to species, it helps to anticipate and prevent complications and decision to give antivenom is helped by correct identification as many harmless snakes may look like venomous snakes. Furthermore, experience tells that description by witnesses are unreliable.

Species diagnosis can be done in several ways

  • Identifying the dead snake
  • Antigen detection by ELISA technique
  • ‘Syndromic approach’ – clinical syndromes
  • Circumstances

Following many public education measures via mass media, the general population is knowledgeable on what to do in event of snakebite. On many occasions they bring the snake to hospital. All medical professionals in the country are trained to identify the venomous snakes and many continuous medical education programmes are carried out in this regard by the authorities. Antigen detection by ELISA is expensive and given the frequency of snakebites, it is not cost effective to be used in routine hospital management other than for research purposes.

When the biting snake is not physically available for diagnosis, the syndromic approach and the circumstances of bite can be used to identify the snake. (annexure 1)

Investigations

The routine investigations that will help in assessment of patient and performed at hospital setting include;

  • Blood urea
  • Serum creatinine
  • Serum electrolytes
  • Full blood count
  • Blood film
  • Urine analysis (UFR – haemoglobin/ myoglobin)
  • ECG
  • Respiratory rate / Tidal volume / Blood gas analysis
  • Input-output charting should be done daily

The 20 minute whole blood clotting (20WBCT) test is a simple bedside test that detects haemotoxicity of envenoming. (See annexure 2). A correctly performed 20WBCT with a positive result i.e. incoagulable blood at 20 minutes is itself an indication to give antivenom therapy.

Antivenom therapy

If the snake identified as a venomous one and if there is a clear cut indication, the next step in management is to start antivenom therapy. The antivenom currently used in Sri Lankan hospitals is imported from India, Haffkine Institute, Mumbai or Serum Institute of India, Pune, Vins Bioproducts, Hydrabad, Bharat Serum, India .

It is an equine serum F(ab’)2 fragment raised against the venom of Indian Russell’s viper, Common krait, Cobra and Saw scaled viper. It is not effective against hump nosed viper and Ceylon krait venom.

Indications for antivenom treatment are;

  • Haemostatic abnormalities: spontaneous systemic bleeding (clinical) coagulopathy(20WBCT or other laboratory evidence) or thrombocytopaenia (<100/ul) (laboratory)
  • Neurotoxic signs: ptosis, external ophthalmoplegia, paralysis etc. (clinical)
  • Cardiovascular abnormalities: hypotension, shock, cardiac arrhythmia(clinical) abnormal ECG
  • Acute renal failure: oliguria/anuria (clinical) rising blood creatinine/ urea (laboratory)
  • (Haemglobin-/Myoglobin-uria) dark brown urine(clinical),urine dipsticks, other evidence of intra vascular haemolysis or generalized rhabdomyolysis
  • (muscle aches &pain , hyperkalaemia) (clinical,laboratory)
  • Supporting laboratory evidence of systemic envenoming

Antivenom administration (minimum dose – 10 vials, each diluted in 10ml of distilled water with 200ml of normal saline, infused intravenously over 1 hour) itself carries a risk of adverse reactions including anaphylaxis and hence should only be used where there is a clear indication. Adrenaline and other medication such as Chlorpheniramine and hydrocortisone is drawn up and kept at bedside during antivenom infusion. Emergency life support equipment is also kept at hand. Patients frequently develop minor reactions to antivenom. In such instances, the infusion is slowed or temporarily halted. The same dose of antivenom is used in children as the snakes inject same amount of venom to both children and adults. Antivenom should not be withheld in pregnancy.

The response to antivenom can be gauged with following observations;

 

·        General; feels better, nausea, headache etc may disappear very quickly

·        Spontaneous systemic bleeding stops within 15-30 minutes

·        Blood coagulability is usually restored in 3-9 hrs

·        Neurotoxic envenoming - post synaptic type may begin to improve in 30 min to several hrs, - pre synaptic type unlikely to respond in this way

·        Active haemolysis & rhabdomyolysis responds in few hours & urine returns to normal colour

·        In shocked patients, BP may increase within the first 30-60 min

 

Criteria to give more antivenom include;

 

·        Persistence or recurrence of blood incoagulability after 6 hours or bleeding after 1-2 hours

·        Deteriorating neurotoxic or cardiovascular signs after 1-2 hours

 

It should be noted that neurotoxic features with envenoming by elapid snakes such as Cobra or Krait may not improve immediately after the initial dose of antivenom. Overtime it will improve gradually without further antivenom therapy.

 

Special considerations in management with regard to specific snakes

 

Krait bites

 

Neurotoxicity with very minimal local envenoming is the hallmark of Krait bites. The severity varies from ptosis, ophthalmoplegia, muscle weakness to respiratory paralysis and death. Respiratory support in form of intubation and ventilation is often necessary. Therefore it is important to transfer the patient to a centre where ICU facilities are available.

 

Cobra bites

 

Cobra bites predominantly cause severe local envenoming and neurotoxicity. Haematological manifestations are not seen. In addition to respiratory support surgical debridement of the bite site may be necessary.

 

Viper bites (Russell’s and Saw scale viper bites)

 

Haemotoxicity and local effects are seen with viper bites. Russell’s viper venom is also known for its neurotoxic, myotoxic and nephrotoxic features. The neurotoxicity is often not severe as in envenoming by elapid snakes.

 

Hump nosed viper bites

 

It causes significant morbidity in urban, semi-urban areas. In acute stage, local effects at bite site and nephrotoxicity with acute renal failure are seen. Overtime chronic complications such as amputations, multiple wound debridements, chronic renal failure is seen. Indian polyvalent antivenom is completely ineffective (Trans R Soc Trop Med Hyg 2007,2008) against hump nose viper venom. Only recommended treatment is conservative management which includes prevention of renal failure and management of renal failure if prevention fails.

 

Ancillary treatment

 

Pain relief with analgesics such as paracetamol and tetanus toxoid is recommended following snakebite. Local effects of toxins can result in muscle necrosis, gangrene, non healing wounds and compartment syndrome requiring surgical intervention.

 

 

 

Rehabilitation

 

Rehabilitation following snakebite is both psychological and physical. Patient education, physiotherapy and occupational therapy are necessary for patients with amputations and prolonged periods of immobilization.

 

Prevention

 

Much emphasis is put on prevention of snakebites in Sri Lanka . Programmes at schools, community centres and via mass media are used to educate people on prevention of snakebite.

 

 

Dr. C.A. Gnanathasan

30 October 2008

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Annexure 1: Syndromic approach to identification of snakes

 

 

Annexure 2: 20 Minute whole blood clotting test

 

·        Place a few milliliters of freshly sampled venous blood in a small glass vessel

·        Leave undisturbed for 20 min at ambient temperature

·        Tip the vessel once

·        If the blood is still liquid (unclotted) and runs out, the patient has hypofibrinogenaemia (incoagulable blood) as a result of venom induced consumption coagulopathy

 

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