Management of snake Envenomation

By: Dr. Hanan Fathy Abdelaziz

Consultant of Clinical Toxicology - Al Qassim P.C.C.

Common Venomous Snakes In Saudi Arabia

Levant viper

Egyptian cobra (Naja haje): 

Puff adder 

Common cobra 

Saw-scaled viper

Clinical picture of Venomenous Snake Bite

Clinical Picture Of Venomous Snake Bite

Viper bite Elapidae biteØ Mainly hemorrhagic.Ø Severe local

reaction.Ø Main manifestations: Local and systemic

bleeding. Hemolysis. Rhabdomyolysis.

O

O Mainly neurotoxic.O Moderated local

reaction.O Main manifestations: Cranial nerve

affection. Skeletal (respiratory)

muscle weakness. Direct cardio toxicity.

Clinical picture of venomous snake bite (cont.)

Viper bite Elapidae bite Ø Main complications

and cause of death:

Pulmonary edema. Hemolysis. Renal failure. Hypotensive shock.

O Main complications and cause of death:

Respiratory failure. Myocardial

depression and cardiogenic shock.

Management of Venomenous Snake

Bite

Venomenous snake bite

In Management Of Venomenous Snake Bite

Before Discussing WHAT TO DO

We Have To Start By NEVER To DO

O

NEVER TO O Apply tourniquet “ All what you do is to

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

IM injection. Cutting increases tissue damage to an area already infiltrated with digestive enzymes.

O Apply any local chemicals, ice or cold packs. It does not slow the enzyme activity. It slows the immune-response.

O Irritate the victim.O Be anxious.

Steps of ManagementO First aid management (in the scene of the

bite).O Transport the victim to hospital.O Assessment and resuscitation.O Decision of ASV.O Observation. (during and after ASV).O Treatment of the bitten area (may need

plastic surgery in viper bite).O Rehabilitation and treatment of

complications.

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

hospital.

Steps of First Aid“R.I.G.H.T ”.

I. Pressure Immobilization Technique

Please pay attention to this video

Start by releasing any tight bandage thenØ R. = Reassure the patient. It is the actual

first aid to slow the circulation down.Ø I = Immobilize (as a fractured limb). Don’t

apply any compression! To spare blood supply.

Ø G. H. = Get to Hospital Immediately. Ø T = Tell the doctor of any systemic

symptoms such as ptosis, bleeding , vomiting etc.. that manifest on the way to hospital.

II. AssessmentClinical Assessment

Factors affecting prognosis:O Site of the bite. Head and neck and

chest are more dangerous.O Time passed since the bite.O Activity at the time of bite.O Amount of venom injected and number

of bites.O Previous state of victim’s health.

Clues Indicating Severe Poisoning

In Elapidae bite:O Early weakness and dyspnea.O Progressive local numbness.In viper bite:O Rapid extension of the local swelling.O Early tender local lymph nodes.O Early spontaneous systemic

bleeding.O Passage of dark brown/black urine.

Severe poisoning means closer monitoring

Laboratory AssessmentFor all cases

Twenty minutes whole blood clotting test (20 WBCT):

O Place 2 ml of fresh venous blood in glass tube without any additives and leave it undisturbed for 20 minutes. Unclotting , is diagnostic of a viper bite (can rules out an elapid bite).

Other hematological tests:O HB% and hematocrit value .O Platelet count.

Biochemical abnormalities: Ø ABGs : Respiratory and metabolic acidosis.Ø Elevated ALT, AST.Ø Bilirubin is elevated following massive

hemolysis.Ø If renal dysfunction occurs there will be

elevated urea , creatinine , K and decreased NaHCO3.

Ø Hyperkalemia and increased CPK (Rhabdomyolysis).

Ø Urine examination: May show RBCs casts and proteinuria.

Pitfalls in diagnosis of envenomation

Common Practical Problems

Common problems in practice are:O Unclear early local signs (snake may

be non poisonous).O Atypical shape of the bite.O Small amount of venom was injected

with no clear systemic signs.O Atypical history.

How to deal with these cases????????

III. The Anti Snake Venom(ASV)

Is not a safe routine line of management

Administration of ASV

How to give anti snake venom?

Polyvalent Versus Monovalent ASVPolyvalent ASV

AdvantagesØ No need to

identify the type of the snake

Ø Less expensive

DisadvantagesØ Higher incidence

of allergic reactions

Monovalent ASV

AdvantagesØ Lower incidence

of allergic reactions.

DisadvantagesØ Needs

identification of snake type.

Ø More expensive.

Administration of ASV Two methods of administration are

recommended:1. Intravenous infusion over one hour.2. Intravenous injection (not commonly used). Other methods: Not recommended and Not

effective: O Local administration : extremely painful and

may increase intracompartmental pressure.O Intramuscular injection: ASV have poor

bioavailability and blood levels never reach the desired level. It is Severely painful with risk of hematoma formation.

Dose of ASV

OAccording to WHO guidelines, initial dose of ASV 100 ml is recommended.

OThe average dose ranges from 5-15 vials.

When to repeat the ASV?????The patient should be observed for:O Spontaneous systemic bleeding and blood

coagulability (20WBCT).O Neurological or cardiovascular symptoms.According to WHO ASV is repeated in cases

of: Ø Uncoagulability after 6 hours (20WBCT).Ø Persistence or recurrence of bleeding after

1-2 hours.Ø Progress of neurotoxic or cardiovascular

signs after 1-2 hours.

Reactions to ASV Ø Early anaphylactic reactions (10 – 180 minutes).Ø Pyrogenic ( endotoxic) reactions (1-2 hours).Ø Late (serum sickness) reactions (1-12 days

average 7 days). Risk of reactions is ASV 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 are under-reported because deaths were attributed to the venom (while patients may not be monitored carefully after treatment).

How To Prevent ASV Reactions?Clinical evidences recommend:

O During administration insert second line and prepare anti anaphylactic measures.

O Slow injection and dilution of ASV. O Careful observation during administration

and for 2 hours after the end of infusion (for early and endotoxic reactions).

O Follow up for 7 days for late systemic reactions.

Common Clinical ProblemO Atypical history of unknown bite.O Atypical shape of the bite.O Minimum signs and /or symptoms

within less than one hour.

The question is Give ASV immediately?

Observe the case?

There are three schoolsFirst school: O Give ASV immediately to all cases.Second schools:O Give ASV immediately to symptomatic

cases and observe suspicious cases.Third school:O Observe suspicious cases.O Giving immediate ASV needs certain

indications.

According to third school:Absolute clinical indications: (Sure sings of considerable envenomation)

Viper bite Elapidae biteO Progressive local

signs.O Spontaneous

bleeding.O Hypotension, shock or

cardio toxicity.O Oliguria or anuria.O Rhabdomyolysis. O Passage of dark urine.

O Any neurotoxicity(specially cranial nerve affection).

O Early weakness and dyspnea.

O Progressive local numbness.

O Hypotension , shock or cardio toxicity.

Absolute laboratory indications: (sure signs of considerable envenomation):

Viper bite Elapidae biteØ INR>1.3. Ø Prolonged PT. Ø Thrombocytopenia

.Ø Elevated urea and

creatinine Ø Hyperkalemia.Ø Metabolic acidosis.

O ECG changes.O Respiratory

acidosis.

Finally what to do???Give or not to give ASV?

O These cases are either non poisonous cases or very minimum amount of venom was injected.

O They are relative indications for ASV.O According to first and second schools you

should administer the ASV.

According to third school:Decision depends on:

O Your clinical evaluation.O Availability of close monitoring and

observation (for immediate intervention).

O Availability of management of all possible complication.

If you choose the third school consider very close observation and monitoring

for 24 hours and ability of rapid interference.

Remember Ø Be quit fast, be quit calm.Ø Pressure immobilization technique.Ø Don’t leave the victim during and after

administration of ASV as its reactions may be fatal.

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