Snake EnvenomationProf Hanan Fathy Abd El Aziz Prof of clinical toxicology Ain Shams University

Common Venomous Snakes In Saudi Arabia

Levant viper:  Characteristics: it belongs to group of true vipers. it is large and dangerous. Its length is average 1 meter, maximum 1.5 meters. Its venom is hemotoxic. Many deaths have been reported from bites of this species. It is a strong snake with an irritable disposition; it hisses loudly when ready to strike.

Egyptian cobra (Naja haje): 

Characteristics: It is extremely dangerous. It is responsible for many human deaths. Its length is average 1.5 meters, maximum 2.5 meters. Once aroused or threatened, it will attack and continue the attack until it feels possible escape. Its venom is neurotoxic and much stronger than the common cobra. Its venom causes paralysis and death due to respiratory failure.

Common cobra (Naja naja): 

Characteristics: A very common species responsible for many deaths each year. Its length is average 1.2 meters, maximum 2.1 meters. When aroused or threatened, the cobra will lift its head off the ground and spread its hood, making it more menacing. Its venom is highly neurotoxic, causing respiratory paralysis with some tissue damage.

Puff adder  (Bitis arietans ):

Characteristics: it is the second largest of the dangerous vipers and one of the commonest snakes. Its length is average 1.2 meters, maximum 1.8 meters. It is largely nocturnal, hunting at night. It is not shy when approached. It draws its head close to its coils, makes a loud hissing sound, and is quick to strike any intruder. Its venom is strongly hemotoxic.

Saw-scaled viper (Echis carinatus): 

Characteristics: A small but extremely dangerous viper. It gets the name saw-scaled from rubbing the sides of its body together, producing a rasping sound. Its length is average 45 centimeters, maximum 60 centimeters. This ill-tempered snake will attack any intruder. Its venom is highly hemotoxic Many deaths are attributed to this species.

Clinical picture of Venomenous Snake Bite

Please pay attention to this video

I. Viper envenomation(Crotalidae)Mainly Hematologic

Local manifestations: (Severe )Severe progressive pain.Petechiae ,oozing from the wound and

formation of blood-filled vesicles.Spreading progressive swelling

(edema) and bruising in bite site (Circumference of the bitten limb should be measured and observed every 15 minutes). Edema extends to cover the whole bitten area.

Gangrene of the bitten area may occur.

Size of bitten area should be marked every 15 minutes

Systemic manifestations:Sweating, nausea, vomitingArrhythmias , Hypotension,

pulmonary edema and shock.Prolonged clotting and bleeding

times.Bleeding gums and bleeding per

orifices e.g. Hematemesis, melena, hematuria etc….

The following manifestations are more common with Russell viper bite:

• Numbness, tingling, cranial nerve dysfunction e.g. (abnormal taste and smell), ptosis and external ophthalmoplegia, paralysis of facial muscles, aphonia, dysphagia .

• Skeletal muscle flaccid paralysis , respiratory paralysis and diminished level of consciousness.

• Loin pain hematuria, haemoglobinuria, myoglobinuria, oliguria/anuria, hyperkalaemia and the condition ends by acute renal failure.

Grading of Pit Viper EnvenomationDry Bite: bite mark without severe pain or swelling , normal

vital signs , normal coagulation studies and normal platelet count.

Mild : Local pain and swelling, normal vital signs , normal to

mildly abnormal coagulation studies and Platelet count >100,000.

Moderate : Local pain and moderate swelling, normal vital signs,

abnormal coagulation studies (double PT and PTT) and platelets <100,000.

Severe: shock ,altered mental status with or without normal

vital signs, abnormal coagulation studies , Thrombocytopenia (platelets <20,000)

II. Coral snakes (Elapidae)Mainly Neurotoxic

Local manifestations ( less than those of viper envenomation) :

Indistinct fang marks.Burning pain (may be absent). Mild to moderate swelling (may be absent)

and discoloration.

Serosanguinous discharge ( may be absent).

Parasthesias around bitten area.Muscular in coordination and weakness in

the bitten limb.

Systemic manifestations: I. Neurotoxicity:Pre paralytic stage:Increased salivation and emesis with or without

headacheParalytic stage:Dysarthria and dysphagia.Visual disturbances ( ptosis and external

ophthalmoplegia). Respiratory distress ends by respiratory failure.

Most deaths occur from respiratory arrest within 36 hours.

II. Cardiotoxicity: Cardio toxins affect the cell membranes directly

causing myocardial depression, cardiogenic shock and systolic cardiac arrest.

Management of Venomenous Snake Bite

First Step

The first step is to identify weather snake is poisonous or not. HOW? The easiest way is to diagnose from the bite.

In both venomenous and non venomenous bites there is universal fear - a state of shock. BUT:

In venomenous snake bite:Site of the bite shows 2 holes ( refer to canines

injecting venom). Spreading pain , numbness and edema.

WHILE in non venomenous snake bite:Bite site shows multiple teeth impressions ABSENT significant local pain or swelling.

After diagnosis of the venomenous bite

To discuss management of venomenous snake bite we

have to start by

DON’T DO Before discussing

WHAT YOU SHOULD DO

NEVER TO Apply tourniquet or bandage “ All what you do is

to localize all digestive enzymes”.Use cut and suck methods. “ Snakebite is an IM

injection. The venom isn’t going to be sucked out. Cutting increases tissue damage to an area already infiltrated with digestive enzymes.

Apply any local chemicals.Attempt to bring the venomous snake to the

hospital. “ it has already bitten one person! There is no medical reason to bring the snake in”. All local species use the same antivenin”.

Use ice or cold packs. It does not slow the enzyme activity. It slows the immune-response.

Irritate the victim.Be anxious.

Steps of ManagementFirst aid management.Transport to hospital.Assessment and resuscitation.ASV.Observing response to anti venom and

deciding weather further doses are needed.

Treatment of the bitten area.Rehabilitation and treatment of

complications.

First aid management Aims of first aid management: First aid management aims to:Retard systemic venom absorption.Arrange rapid transport of the victim

to hospital.

Steps of First Aid

“Do it R.I.G.H.T ”.(pressure immobilization

technique)Please pay attention to this video

Start by releasing any tight bandage.R. = Reassure the patient. Calming the

patient is the actual first aid very to slow the circulation down.

I = Immobilize in the same way as a fractured limb. Use bandages or cloth to hold the splints, not to block the blood supply. Do not apply any compression!

G. H. = Get to Hospital Immediately. Traditional remedies have NO PROVEN benefit in treating snakebite.

T= Tell the doctor of any systemic symptoms such as ptosis, bleeding , vomiting etc.. that manifest on the way to hospital.

Clinical Assessment Factors affecting prognosis:Site of the bite. Head and neck and chest are more

dangerous.Time passed since the bite.Activity at the time of bite.Amount of venom injected.Previous state of victim’s health.

Clues indicating severe poisoning:Rapid early extension of local swelling from the site of

the bite.Early tender enlargement of local lymph nodes.Early systemic symptoms as hypotension, nausea,

vomiting , severe headache etc...Early spontaneous systemic bleeding and / or

passage of dark brown/black urine.

Laboratory Assessment20 minutes whole blood clotting test 20

WBCT:Place 2 ml of fresh venous blood in ordinary

glass tube without any additives and leave it undisturbed for 20 minutes.

If the blood is still unclotted, this is diagnostic of a viper bite and rules out an elapid bite.

N.B : If the used vessel is not made of ordinary glass, or if it has been cleaned with detergent, the test will be invalid and should be repeated.

Other hematological tests:HB% , hematocrit value and Platelet count.Color of Plasma / serum: may be pinkish or

brownish if there is or hemoglobinemia or myoglobinemia.

Biochemical abnormalities: Elevated Aminotransferases and muscle

enzymes.Bilirubin is elevated following massive

hemolysis.If renal dysfunction occurs there will be

elevated Urea , creatinine , potassium and decreased sodium bicarbonate.

Early hyperkalaemia may be seen following extensive rhabdomyolysis.

ABGs : may show evidence of respiratory failure in neurotoxic envenomation and in case of acidosis.

Urine examination: urine should be examined for :

Color , Red cell casts and proteinuria.

The Anti Snake Venom(ASV)Anti venom is the only specific antidotefor snake venom A most important decision in the management of a snake-bite victim is whether or not to administer anti venom

Rules of Giving ASVAnti venom should be given only to patients

in whom its benefits exceed its risks. The risk of reactions should always be taken

into consideration. Patients having +ve history of atopic diseases (e.g severe asthma) are at high risk of severe reactions and should be given ASV under close monitoring during and after treatment.

Anti venom treatment should be given as soon as it is indicated. It may reverse systemic envenoming even after several days up to 2 or more weeks. It is, should be given as long as coagulopathy persists.

Indications of ASV Local indications:Local swelling involving more than

half of the bitten limb (in the absence of a tourniquet) within 48 hours of the bite.

Rapid extension of swelling within a few hours of bite on the hands or feet.

Development of an enlarged tender lymph node draining the bitten area.

Systemic indications: Clinical indications:Spontaneous systemic bleeding.Neurotoxic signs: ptosis, external

ophthalmoplegia, paralysis etc….hypotension, shock, Cardiac arrhythmia

and /or Abnormal ECG.Oliguria and / or anuria.Rhabdomyolysis. Laboratory indications : Positive 20WBCT .

Prolonged PT. Thrombocytopenia (<100 000/cu mm). Elevated urea and creatinine and hyperkalaemia.

Types of Reactions to ASV Usually more than 10% of patients receiving ASV

develop one of the following reactions: Early anaphylactic reactions (10 – 180 minutes).Pyrogenic ( endotoxic) reactions (1-2 hours).Late (serum sickness) reactions (1-12 days

average 7 days). Risk of reactions is dose-related, except if the

victim has been sensitized e.g. to equine anti venom or rabies-immune globulin.

These reactions may be fatal but fatalities have probably been under-reported as death is usually attributed to the venom while patients may not be monitored carefully after treatment.

Prevention of ASV Reactions There is no prophylactic regimen that has been

effective in clinical trials but there are some evidences recommend the following:

Prophylactic drugs e.g. adrenaline , anti H1 blockers and corticosteroids. ( adrenaline is the best).

Speed and dilution of ASV administration. Since no prophylactic regimen has proved

effective, these drugs should be used only in high risk patients. All patients should be carefully observed for two hours after the completion of ASV administration and treated with adrenaline at the first sign of a reaction.

Polyvalent Versus Monovalent ASV

Polyvalent ASVAdvantages

•No need to waste time or effort to identify the exact nature of venomous snake•Less expensive•Easy distribution to all parts of the country

Disadvantages• Decreased efficacy (?)

•Increased incidence of allergic reactions

Monovalent ASV

Advantages•Increased efficacy•Lower incidence of allergic reactions

Disadvantages•Identifying the exact nature of venomous snake mandatory•More expensive if all snakes need to be covered snake venom required in various regions of India.

Administration of ASV Two methods of administration are

recommended:1. Intravenous injection: In this method the

administer must remain with the patient during time of early reactions (up to 180 minutes).

2. Intravenous infusion over one hour. Other methods: Not recommended and

Not effective: Local administration : It is extremely painful,

may increase intracompartmental pressure. Intramuscular injection: ASV have poor

bioavailability , So blood levels never reach the desired level. Severely painful with risk of hematoma formation.

ASV DosesThere is great controversy regarding

initial dose of ASV due to lack of study on this issue.

The initial dose should neutralize most of the of venoms injected.

WHO recommended, initial dose of polyvalent ASV is 100 ml. It will neutralize 60 mg of Russell’s viper venom and cobra venom , 45 mg of krait and saw-scaled viper.

The average dose ranges from 5-15 vials.

After Administration of ASV

The victim should be observed for:General condition.Spontaneous systemic bleeding and blood

coagulability (20WBCT).Neurological or cardiovascular symptoms.Urine color. Criteria to repeat the ASV: Uncoagulability after 6 hours (20WBCT).Persistence or recurrence of bleeding after 1-

2 hours.Deteriorating neurotoxic or cardiovascular

signs after 1-2 hours.

Finally The snake says: Don’t threat me The victim immediately after the bite

says: Don’t stress me The victim during and after

administration of ASV says: Don’t leave me And I say: Don’t forget me

Thank you