Conference Lectures

Management of Snake Bites Current Concepts

Prof.N.Ganapathy, M.B.B.S., D.A., M.D., F.C.C.P., D.C.C.M. (Cardiology), M.C.A.M.,
Critical Care Physician,
National Director, Comprehensive Trauma Life Support International Course,
International Trauma Care (Indian Chapter),
Director, Dhanvantri Institute of Medical Education & Research,
Dhanvantri Hospitals / Dhanvantri Critical Care Center,
Specialist in Clinical Toxicology & Snake Envenomation,
27, 28, Poongundranar Street, Karungalpalayam, Erode 638 003,
Tamil Nadu, India.

Introduction
There are four types of Poisonous Snakes in India. They are Cobra and Krait (Elapidae), Russell’s Viper, and Saw Scaled Viper (Viperidae). These snakes are responsible for most of the deaths in India. So they are called “The Big Four.” Now Hump Nosed Viper in Kerala and in Western Ghats produces more deaths. Now the terminology “Big Five” is used.
The Elapidae are normally Neurotoxic and the Viperidae are Hematotoxic, Nephrotoxic although rarely they may overlap.
Onsite Primary Survey
The goals of primary survey are:

  • To retard systemic absorption of venom
  • To preserve life and prevent complications before the patient can receive medical care.
  • To control distressing or dangerous early symptoms of envenoming
  • To arrange rapid transport of the patient to the hospital

What to do?

  • Reassure the patient.
  • Limb should not be excited and move about
  • Limb should not be massaged
  • Limb should be kept at rest

Pressure immobilization method:
An elasticated, stretchy, crepe bandage, approximately 10cm wide and at least 4.5 meters long should be used. The bandage is firmly around the entire limb, starting distally around the fingers or toes and moving proximally, to include a rigid splint. The bandage is bound as tightly as for a sprained ankle, but not so tightly that the peripheral pulse (radial, posterior tibial and dorsalis pedis) is occluded or that a finger cannot easily slipped between its layers.
Pressure immobilization is recommended for bites by neurotoxic elapid bites but should not be used for viper bites for it increases the local effects of necrotic venom.
What not to do?
There is no role for:

  • Local incisions
  • Attempt to suck the venom
  • Tight arterial tourniquet
  • Topical instillation or application of chemicals, herbs or ice packs
  • Most traditional first aid methods should be discouraged as they do more harm than good

Anti-Snake Venom
Indications

  • ASV should not be used without evidence of envenomation
  • It is administered when a patient with suspected snake bite develops the following    symptoms:
  • Systemic envenomation
  • Local Envenomation
  • Systemic envenomation
    • Haemostatic abnormalities
      • Clinically if there is spontaneous systemic bleeding
      • Laboratory investigations reveal Coagulopathy (20 WBCT positive) or Thrombocytopenia (<100 x 10/L)
    • Neurotoxic Signs
      • Clinically if there are Ptosis or Respiratory Paralysis
    • Cardio-Vascular Abnormalities
      • Clinically if there is evidence of Arrhythmias, Cardiac failure, Hypotension or Shock
      • ECG Changes
    • Renal Abnormalities
      • Clinically if there is Oliguria, Anuria, dark brown urine (hemoglobinuria / myoglobinuria, Muscle aches (hyperkalemia)
  • Local Envenomation
  • Local swelling involving more than half of the bitten limb (in the absence of a tourniquet)
  • Swelling after bites on the digits (toes and especially fingers)
  • Rapid extension of swelling (e.g., beyond the wrist or ankle within a few hours of bite on the hand or feet)
  • Development of an enlarged tender lymph node draining the bitten limb

Anti-Snake Venom is given only by Intravenous Route.

Recent trends in Anti-Venom Therapy

  • Clinical experience reveals that the injected snake venom is released from site to circulation for many days.
  • This is due to:
    • Continuous absorption of venom from the “depot” at the site of bite, assisted by improved blood supply following correction of hypovolemia and shock
    • A redistribution of venom from the tissues into the vascular space
  • So, ASV should be given over a period of days till systemic manifestations persist.

ASV is given 20ml sixth hourly till:

  • Hemorrhagic manifestation stops
  • Extend of the swelling stops (progression of the cellulites is reduced)
  • Hemodynamically stable
  • No evidence of arrhythmias and cardiac failure
  • Ventilator independent

Treatment for Antivenom Reaction

  • Suspend ASV administration
  • Epinephrine 1mg/ml Intramuscular is the drug of choice
  • It is followed by chlorphenaramine maleate 10mg intravenous injection and 100mg of hydrocortisone

Plasmapheresis in Snake Envenomation

  • Plasmapheresis is used as an adjuvant treatment in Snake envenomation as the      Snake Venom is circulated in the Plasma.
  • 20% Human Albumin is used as substitution fluid
  •  Albumin is preferred to Plasma  because :
    • It reduces the risk of hypersensitivity reactions
    • Prevents transmission of blood borne infection
  • 100 ml of Human Albumin is generally combined with 400 ml of 0.9% Normal Saline
  • 2000 ml of plasma is removed and replaced with Human Albumin  and 0.9% Normal Saline
  • Two such Cycles of Plasmapheresis are done first cycle after six hours following the bite and second cycle on the second day, with the hypothesis that the injected venom is primarily absorbed by lymphatics and later drained to blood. The delay of six hours is for allowing time to Plasmapheresis procedure to access the venom in the blood.
  • Advantages of Plasmapheresis
    • Decreases the venom induced toxicity
    • Most of the time Anti-snake Venom is not required after Plasmapheresis or less dose is needed
    • Results in rapid reduction in swelling and avoids Compartmental Syndrome
    • Correction of Venom Induced Consumption Coagulopathy (VICC)
    • Reduces the frequency of Dialysis in Snake Bite Induced Acute Kidney Injury (AKI)
    • Correction of Snake Bite induced Sepsis and Septic Shock
    • It reduces the patient days on Ventilator support
    • It overall significantly reduces morbidity and the cost of hospital stay

Neuroparalytic Complication in Snake Envenomation
Cobra

  • In elapid bites Cobra the offending toxin produces non-depolarizing type of neuromuscular block.
  • Ptosis is the first outward manifestation of the neuromuscular block.
  • 3.0mg neostigmine along with 1.5mg of atropine Sulphate should be given slowly intravenously initially. This is followed by one third the initial dose every second hourly intravenously and the dose is gradually tapered. Premature discontinuation will lead to relapse
  • This should be followed by simultaneous administration of ASV
  • As atropine has the tendency to produce as delirium, Neostigmine - Glycopyrrolate combination is used
  • If neostigmine atropine combination does not reverse neuromuscular block and if the paralysis of the respiratory muscle occur then the patient requires Ventilatory Support
  • Usually Ventilatory Support is required for around 10 days for Elapid Snake Bite.
  • But with two cycles of Plasmapheresis the patient can be weaned from the Ventilator.

Krait

  • Krait snake has a nocturnal habitat
  • As the fangs are soft it does not produce pain, swelling or mark at the bitten site
  • The patient become areflexic and has fixed dilated pupils. So the patient should not be diagnosed as brain death
  • Further it produces axonal damage and the paralysis is predominantly presynaptic and hence the ASV and Neostigmine – Atropine drugs will not act in Krait Envenomation. Recovery depends on the axonal repair

Coagulopathy in Snake Envenomation

  • Coagulopathy is usually seen in Russell’s viper Bites in South Asian Countries.
  • It is coined as Venom Induced Consumption Coagulopathy (VICC).
  • Bleeding from the gums is the first outward manifestation of VICC.
  • If platelet is less than 50,000/mm3, 2 units of Fresh Frozen Plasma (FFP) or platelet concentrate is transfused every day till platelet counts starts improving
  • Current trend is to start Anti-Snake Venom 40 ml sixth hourly followed by 20 ml sixth hourly with two units of Fresh Blood at twelfth hourly interval.
  • The Coagulopathy gets corrected within 24 to 36 hours in 95% of the patients.
  • Transfusing Whole Fresh Blood Transfusion takes care of the VICC and also provides adequate Hemoglobin for Oxygen transport
  • Because of the unavailability of whole fresh blood the components are used
  • It is assessed by repeating 20 WBCT every six hours.
  • If the patient is in AKI blood is given during dialysis to avoid fluid overload.
  • The following criterion denotes Severe Coagulopathy:
  • INR > 3.0
  • aPTT> 50secs
  • Platelets < 50,000cel/cu.mm
  • Fibrinogen <75mg/dl

Acute Kidney Injury

  • Acute Tubular Necrosis usually occurs in viper bite
  • Treated by restoration of fluid and electrolyte balance
  • 500mg of frusemide intravenously
    • In a syringe pump at 4 ml/hour. (Around Six hours)
    • Frusemide converts Oliguric phase of Renal failure  to Diuretic phase
    • Usually diuresis occurs within two to four hours
  • If renal shutdown occurs, hemodialysis is contemplated. Early prophylactic haemodialysis will improve survival
  • Femoral catheter must be the vascular access for the haemodialysis (As snake bite victims are prone for bleeding abnormalities subclavian and internal jugular veins as vascular access may prove detrimental)
  • If haemodynamically unstable CVHD / CVVHD can be instituted

 

Abdominal Scan as a Tool for Haemodialysis

  • Like Focused Assessment with Sonography for Trauma (FAST), Focused Assessment with Sonography for Snake Bite (FASSB) has emerged as a significant tool for patient with renal dysfunction secondary to nephrotoxic snake venom
  • Within 2 to 4 hours after envenomation, which is nephrotoxic the abdomen scan reveal poor cortico-medullary differentiation indicating Acute Tubular Necrosis (ATN)
  • The Urea and Creatinine raises only after 12-24 hours
  • Early prophylactic dialysis is indicated when there are changes in the kidneys, even if urea and creatinine were found to be normal for the ultimate early outcome
  • The measurement of the IVC in sub-costal view is an indirect evidence of central venous pressure. The IVC should be maintained between1.6-2.0 cm. If it is below 1.6cm it reveals dehydration and above 2.0 over hydration.
  • In Renal Doppler, if the Renal Index (RI) is more than 0.75, it denotes AKI which is revealed within 6 hours of Nephrotoxic Snake Envenomation 

Necrotizing Fasciitis in Snake Bites

  • Fasciitis involves the subcutaneous tissue and deep fascia
  • The clinical presentation may be masked, as changes in the overlying skin may only be observed later in the disease process
  • Signs and Symptoms
    • Pain out of proportion to examination
    • Bullae
    • Systemic toxicity
    • Serum Sodium < 135 mmol/L
    • WBC > 15, 400 cell/mm3
    • Tenderness beyond the area of Erythema
    • Crepitus
    • Cutaneous Anaesthesia
    • Cellulitis refractory to antibiotic therapy
  • Magnetic Resonance Imaging (MRI) may delineate the extent of the infection and has a high sensitivity for detection of necrotizing soft tissue infections
  • Management
  • These are lethal disorders
  • Patient should undergo immediate surgical debridement
  • Broad Spectrum antibiotics that cover Gram Positive Cocci, Gram Negative Bacilli and Anaerobes should be used

Septic Shock in Snake Bites

  • SIRS
  • Sepsis &
  • Septic Shock

Is very common in Russell’s Viper Envenomation and is challenging to treat

Take Home Message

  • Anti-Snake Venom when it is indicated
  • Anti-Snake Venom has got its own Side Effects
  • Neostigmine and Glycopyrrolate or Atropine to neutralize the Non depolarization muscle relaxant  effect in Cobra Envenomation
  • Krait Envenomation is mostly presynaptic and if axonal damage occurs Anti-Snake Venom is of no use
  • Mechanical Ventilation in Ventilatory failure in Elapid Bites
  • Renal Replacement Therapy in Viper Envenomation
  • Fresh Whole Blood for & Blood Products for VICC
  • Identifying Early Sepsis (ISE) and Early Goal Directed Therapy in Sepsis
  • Plasmapheresis may become the First Line of Treatment  in Snake Envenomation

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