Snakebite

SNAKEBITE

I. INTRODUCTION

Snakebite is one of the most neglected public health issues in the poor rural communities living in

Cambodia. The true burden of snakebite is not known because of large-scale misreporting.

Cambodia is a heavily affected region due to widespread agriculture activities with home environmental exposure to hidden place of snakes, numerous venomous snake species and lack of functional snakebite control programs.

Snake envenoming is a potential life threatening condition. It is characterized by systemic effects ranged from non-specific signs such as nausea, vomiting to coagulopathy, neurotoxicity, myotoxicity and renal damage [1, 2].

In Cambodia, snakebites increase perceptibly during the rainy season particularly in provinces along the Mekong and Tonle Sap floodplains [3]. Despite this perception, snakebite incidence, disability, mortality are not currently reported due to lack of accurate data within health referral offices as well as the Ministry of Health. A majority of snakebites injuries are not treated in health facilities and naturally the victims seek traditional healers [3].

Seeing the burden and complications of envenomed cases with a challenging outcome of snakebites under conventional treatment by antibiotic application and surgical procedures (debridement, Fasciotomy), Kantha Bopha Hospital has adapted a protocol of treatment based on specific antivenom serums since the beginning of year 2010. Over the year 2010, 46 snakebite cases which were subjective to a retrospective study, were treated in Kantha Bopha Hospital- Phnom Penh.

II. DEFINITION

According to the International Classification of Diseases code (E905 and E906) for bites and

stings, a snakebite is definite if a snake bit or spat and was seen, probable if a snake was seen nearby with fang marks or clinical effects suggestive of snakebite without fang marks and possible if a snake was not seen but definite fang marks were found [4].

Ø  Dry bites are bites not accompanied by any local effect because no venom is injected or the snake is non-venomous [5].

Ø  Local envenoming is defined as only local effects such as pain, swelling, blisters or tissue necrosis without systemic abnormalities because insufficient venom is injected [1, 2].

Ø  Systemic envenoming is defined as both local effects and at least one of coagulopathy, neurotoxicity, myotoxicity and renal impairment or non-specific signs (nausea, vomiting, abdominal pain, dizziness and headache) [1, 2].

III.EPIDEMILOGY [6]

Venomous snakes of Cambodia

Cambodia  shares  many  aspects  of  its  venomous  snake  fauna  with  neighbouring  Thailand,

Vietnam and Laos. There are approximately 86 different snake species including 17 species that are known to be venomous [6]. Among 17 venomous snakes, 6 species are responsible for the majority of all severe illness and 5 species can cause potentially fatal illness. Cambodia’s venomous snakes belong to 2 main groups such as Elapidae and Viperidae that are easily distinguished on the basis of external morphology:

IV. PHYSIOPATHOLOGY [6]

Actions of snake venom

General effects of snake venoms

—    Cytotoxins: destroy cell tissue by increasing membrane permeability and cell membrane hydrolysis & proteolysis

—    Haemorrhagins: damage blood vessel walls

—    Haemolysins: damage blood cell membranes

—    Procoagulant toxins:

-     disruption of normal haemostasis by causing abnormal activation of blood clotting factors

-      factor depletion ( consumptive coagulopathy)

—    Platelet toxins: destroy platelets, may either initiate aggregation or inhibit aggregation.

—    Neurotoxins:

α-neurotoxins (postsynaptic- reversible) block acetylcholine binding to receptors in neuromuscular synaptic

β-Neurotoxins (pre synaptic- irreversible) target nerve terminals and destroy them from inside after being internalized by endocytosis

—    Myotoxins:  Rhabdomyolysis can lead to indirect nephrotoxicity due to accumulation of cellular debris in kidney nephrules

—     Nephrotoxins: induce direct nephrotoxicity by causing renal tubular necrosis

—    Cardiotoxins: poisoning general myocardial cell membranes causing irreversible cellular depolarization.

*** Commonly bites by the Viperidae result in hemotoxicity while bites by the Elapidae cause neurotoxicity.

Understanding the actions of venoms of each type of snake can sometimes help identification of the species responsible.

V. SYMPTOMATOLOGY [1, 3]

1- Symptoms & signs of Viper bite (Hematotoxic snake):

o Dry bite: no local effects

o Local envenoming: starts progressively in hours after bite: pain-edema-blisters-necrosis

o Systemic envenoming:

-Coagulopathy: Local bleeding, systemic bleeding (skin ecchymosis –

gum bleeding, GI bleeding)

-Nephrotoxicity: Russel’s viper can cause nephrotoxicity and neurotoxicity. Severe rhabdomyolysis often cause renal failure

2- Symptoms & signs of Elapid bite (Neurotoxic snake):

o Dry bite: no local effects

o Local envenoming: starts progressively in hours after bite: pain-edema-blisters-necrosis

(for cobras), numbness (for kraits)

o Systemic envenoming:

-Neurotoxicity: starting from drowsiness to descending paralysis: face-respiratory –trunk

& limb Blurring of vision, pupillary abnormalities (some patients may have long-term pupil dilation after krait envenoming), abnormalities of taste & smell (may persist for many months after bite), urinary retention

-Cardiotoxicity:  arrythmias:

VI. DIAGNOSIS [6]

6.1. Snakebite identification

Ø  Identify the likely snake responsible for bite: Have the victim or entourages describe or point the snake species (on pictures of snakes) that he or they have seen on spot.

Ø  Usually two fang marks are found.

Ø  All patients will be  kept the patient  under 24 h observations

Ø  Determine the exact time of the bite

Ø  Timing of onset of toxinodromes after bite

o Coagulopathy: 1-2h.

o Neurotoxicity: 3-4h

o Cytotoxicity- Myotoxicity: hours

o Nephrotoxicity: 12-24h.

o Cardiotoxicity : 2-6h

6.2. Presumptive identification

6.3. Laboratory investigations

Ø  20-minute whole blood clotting test (20’ WBCT)

If the 2 ml of freshly sampled venous blood in a small, dry, glass vessel left undisturbed for 20 minutes is still unclotted and runs out, the patient has hypofibrinogenaemia as a result of venom-induced consumption coagulopathy. In Cambodia, incoagulable blood is diagnostic of a viper bite and rules out an elapid bite.

Ø  Prothrombin Time (PT): Normal range is 12-16 seconds.

Ø    Partial Thromboplastin Time (PTT): Normal range is 25-47 seconds.

Ø  Fibrinogen  level:  Normal  range  is  1.5-4.5  g/L.  In  DIC  involving  defibrination,  the fibrinogen level will be critically below these ranges, and is often undetectable.

Ø  Fibrin-degradation products (FDP):

defibrination, the FDP levels may be extremely high.

Ø  Whole blood cell count

Ø  CK, Kaliemia ,Urea-Creatinemia

Ø  ECG, X ray- Ultrasound- CT scan (If distant bleeding is suspected)

VII- FIRST AID TREATMENT PROTOCOL

7.1. Recommended Method for Cambodia: “Do it R.I.G.H.T”

Ø  Reassure the patient: 80% of all Cambodian snakes are non- venomous.

Only 60% of bites by venomous species actually envenomate the patient

Ø  Immobilize in the same way as a fractured limb, use bandages

Ø  Get to Hospital immediately

Ø  Tell the doctor of symptoms

7.2. Discarded Method

Ø  Tourniquets

Ø  Cutting and Suction

Ø  Electrical Therapy and Cryotherapy

7.3. Newer Method

Ø  Immobilisation for viper bites or unidentified snakebite

Ø  Pressure Immobilisation bandages (PIB) for Elapid bites

7.4. Snakebite Prevention

Ø  Footwear

Ø  Use a torch at night

Ø  Walk with a heavy step

Ø  Pay close attention to the leaves and sticks collecting

Ø  Avoid sleeping on the ground

VIII. SNAKEBITE TREATMENT PROTOCOL

8.1. Patient assessment on arrival

Ø  Resuscitation of ABC (Airway, Breathing, Circulation)

Ø  Tetanus vaccination (after ASV if clotting disorder)

Ø  Antibiotics: Ceftriaxone(100mg/kg/day)+ Metronidazole(30mg/kg/day) if large wound injuries

Ø  Pain killer: Tylenol (20mg/kg/dose)

Ø  Handling Tourniquets: sudden removal of the tourniquet can lead to hypotension/ respiratory distress due to massive surge of venom, but it is safe to remove it slowly or after ASV (anti-snake venom).

8.2. Antivenom treatment

8.2. 1. Choice of anti-snake venom (ASV)

  8.2.2. ASV indication: Best results when given early! Never delay! If either:

o Severe current local envenoming (swelling>50% of the limb) or

o Systemic envenoming: coagulopathy, neurotoxicity, cardiotoxicity nephrotoxicity,

rhabdomyolysis

8.2.3. ASV dosage- no ASV test doses

Children should receive the same initial dose of ASV as adults, as snakes inject the same amount of venom into children as adults.

8.2.4. Treatment of ASV reactions

ASV reactions: fever, chills, urticaria, itching or itchy throat. Monitor closely vital signs during infusion of ASV: watch for stridor, wheezing, dyspnea, syncope or arrythmias.

1- Discontinue ASV

2- H1 Antihistamine: Promethazin/ Chlorpheniramine maleate (0.2mg/kg IV) + Paracetamol PO (20mg/kg/dose)

3- Hydrocortisone IV: 10mg/kg

4- Restart ASV after recovery.

5- Adrenaline IM 0,01mg/kg is reserved for moderate to severe anaphylaxis.

8.2.5. Recovery phase

Reassessment, if an adequate dose of appropriate ASV:

a) Systemic bleeding stops within 15-30 mn.

b) 20’WBCT (-) in 6 h.

c) Paralysis by Cobra improves in 30’ or hours.

d) Paralysis by Krait improves in considerable time

e) Active haemolysis & rhabdomyolysis cease within a few hours f) Shock disappears after 30 mn.

g) Rising platelet rate is not significantly accelerated and blood CK was not     decreased after ASV.

8.2.6. Repeat ASV doses

o Persistent bleeding:

-Same dose every 6h until coagulation has been restored (max dose: 30 vials)

-Vitamin K (10mg IV)/ others haemostatic agents

-Use Fresh Frozen Plasma if available.

-Blood products: only use if severe uncontrollable bleeding or adequate ASV has been given

o Persistent neurotoxicity:

-Same dose after 1-2h (maximum dose: 20 vials)

-Neostigmine IM (0,04mg/ kg) + Atropine IV (0,05mg/kg) half hourly x 8h

(Neostigmine is an anticholesterase that prolongs the life of acetycholine and can therefore reverse the respiratory failure and neurotoxic symptoms.

8.2.7. Others treatments

Ø  Rhabdomyolysis:

-Mild (no complication): Rehydration

-Severe: Alkalinize urines by IV fluids (30ml of 8, 4%NaHCO3/l of serum) or hemodialysis

Ø  Hyperkaliemia:

-Mild (no ECG changes): Diet, stop medications responsible

-Severe: Diuretic (Lasix: 1mg/kg/dose) or (Glucose and Insulin, Ca, NaHCO3)

Ø  Hypotension:

Beside a number of causes, Russell’s viper is known to cause acute pituitary adrenal

insufficiency. So Dopamine and Hydrocortisone are helpful.

Ø  Renal failure: Diuretic, Dialysis. ASV has no efficacy

Ø  Serum sickness: Antihistaminic/ Prednisolone(1mg/kg/day) x 5days

Ø  Wound care

-Prevent rupture of bullae; aspirate aseptically if large

-Clean skin daily gently with Betadine or soap & water

-Elevate limbs to reduce bleeding & swelling

Ø  Surgical intervention : when stable after ASV:

-Debridement: if tissue necrosis

-Fasciotomy: if compartment syndrome

-Skin Grafting: if loss of tissues

-Amputation: if gangrene

Ø  Rehabilitation & Follow-up: kinesis, next tetanus toxoid dose.

REFERENCES

[1]- Isbister GK. Snake bite: a current approach to management. Aust Prescr [serial on the Internet]. 2006 [cited 2010 Jan 15]; 29:125-9. Available from: http://www.australianprescriber.com/magazine/29/5/125/9.

[2]- Currie BJ. Snakebite in tropical Australia: a prospective study in the "Top End" of the Northern

Territory.  Med J Aust. 2004 Dec 6-20;181(11-12):693-7.

[3]- Warrel DA. Guideline for the clinical management of snake bite in the South East Asia region [homepage on the Internet]. Geneva: World Health Organization; [updated 1999; cited 2010 Jul 29]. Available from: http://www.searo.who.int/LinkFiles/SDE_mgmt_snake-bite.pdf.

[4]- Tan HH. Epidemiology of snakebites from a general hospital in Singapore: a 5-year retrospective review (2004-2008). Ann Acad Med Singapore. 2010 Aug;39(8):640-7.

[5]- Alirol E, Sharma SK, Bawaskar HS, Kuch U, Chappuis F. Snake bite in South Asia: a review.  PLoS Negl Trop Dis. 2010 Jan 26;4(1):e603.

[6]- Williams DJ, Jensen SD, O’Shea M. Snake bite management in Cambodia: towards improved prevention, clinical treatment and rehabilitation [homepage on the Internet]. Geneva: World Health Organization; [updated 2009; cited 2010 Jun 23]. Available from: http://garudam.info/files/WHO2009- Cambodia.pdf.