Snake envenomation and its management

Ramu. V

Emergency Department, Kauvery hospital, Cantonment, Trichy

Introduction

Envenomation vs Poisoning

Ronald’s rule: ‘If you bite it and you die it’s poison, but if it bites you and you die, that’s venom’.

VenomPoison
It's introduced via a woundNo wound involved.
It can be injected through a number of means, including teeth, a sting, spines or claws.It can be absorbed into the bloodstream through the skin, inhaled or ingested

Epidemiology

Global incidence of snake bite is around 5.4 million with about 1.8 to 2.7million envenomation. South Asia is 70%, and India reports around 2-3 lakhs bites annually. In 2017, WHO listed snakebite envenoming as a Priority Neglected Tropical Disease.

As per Central Bureau of Health Intelligence (CBHI), in India there are approximately 3,00,000 snakebite cases resulting in 2000 deaths annually. Only 7.3% snake envenomation deaths were officially reported. Only 23% deaths occurs in hospitals. Others were unreported

Factors for high death rate in India

  • Only 22.19% snake bite patients reache hospital
  • 7 % deaths were due to common krait bite [1] Majumder et al, 2014
  • 7% received first aid at the site and 20.25% reached hospital after native treatment (ozhas, or mantrik and tandrik)- as reported by [2] Sing et al.

Poisonous Snakes of India

Among 3509 snake species, and  310 documented in India, only four have been identified as primary contributors to life-threatening snakebites- termed the “Big four,”

  • The spectacled cobra (Naja naja)
  • Russell’s viper (Daboia russelii)
  • Common krait (Bungarus caeruleus)
  • Saw-scaled viper (Echis carinatus).

Distribution Range of the snakes

  • Saw scaled viper
  • Common krait
  • Russel’s viper
  • Cobra

  • Monocled cobra
  • King cobra
  • Banded Krait
  • Hump nosed pit viper

Spot the difference

  • Elapidae: Neurotoxic syndrome
  • Viperidae: Vasculotoxic. Early, Pain, swelling, oozing out of wound
  • Colubridae: Late internal bleeding and AKI.

Snakebite Envenomation, essential principles of management

  • First aid treatment
  • Transport to hospital
  • Rapid clinical assessment and resuscitation
  • Investigations/laboratory tests
  • Clinical assessment and species diagnosis, if possible
  • Antivenom treatment
  • Observing the response to antivenom
  • Deciding whether further dose(s) of antivenom are needed
  • Supportive/ancillary treatment
  • Treatment of the bitten part
  • Follow-up
  • Rehabilitation

First Aid after Snakebite

Bitten by snake
Reassure
Immobilise
Avoid tourniquet
NPO
Don’t waste time finding and killing snake
Don’t waste time in seeking native treatments
Bike ambulance
Reach nearby PHC

Myth busting

Don’t

Do’s

Pressure between 40- and 70-mm Hg in the upper extremity and between 55- and 70-mm Hg in the lower extremity – slows lymph flow.

In emergency department

Check whether patient is

  • Critical on arrival
  • Symptomatic on arrival
  • Asymptomatic on arrival

Critical

Early clues that a patient has severe envenoming (including pregnant): WHO

  • Snake identified as a very dangerous one.
  • Rapid early extension of local swelling from the site of the bite.
  • Early tender enlargement of local lymph nodes, indicating spread of venom in the lymphatic system.
  • Early systemic symptoms: collapse (hypotension, shock), nausea, vomiting, diarrhoea, severe headache, “heaviness” of the eyelids, inappropriate (pathological) drowsiness or early ptosis/ophthalmoplegia.
  • Early spontaneous systemic bleeding.
  • Passage of dark brown/black urine

Symptomatic

Neuroparalytic symptoms: Cobra/Krait

  • Develops within 30 min – 6 hr in cobra and 6–12 hr in Krait bite
  • Ptosis, Diplopia, Dysarthria, Dysphonia, Dyspnoea, Dysphagia – paralysis of intercostal and skeletal muscles occur
  • Diminished or absent deep tendon reflex and head lag may present.

Identify impending respiratory failure

  • Single breath count – number of digits counted in one exhalation – >30 normal
  • Breath holding time – breath held in inspiration – normal > 45 sec
  • Ability to complete one sentence in one breath.

Vasculotoxic: Viper bites

  • Systemic manifestations
  • Life threatening complications
  • Painful progressive swelling (PPS)

Systemic manifestations

  • Elevated Whole Blood Clotting Time (WBCT) , normal is 8 to 15 mts, (Due to consumptive  coagulopathy) develops as early as 30 min

The 20 min whole blood clotting test (WBCT20) is a simple bedside test of coagulation that requires only a clean glass tube to perform and is routinely used to identify and treat patients with clinically significant venom-induced consumption coagulopathy (VICC).

A clean, dry glass bottle or vial into which 1-2 millilitres of venous blood is added, is allowed to stand at room temperature for 20 minutes, and is then inverted and the presence or absence of a complete clot is recorded.

  • Acute abdominal tenderness – GI or retroperitoneal bleed
  • Asymmetric pupil and neurological signs – IC bleeding
  • Visible systemic bleeding

Life threatening complication

Renal involvement

  • B/L renal tenderness
  • Hematuria
  • Hemoglobinuria
  • Myoglobinuria
  • Oliguria/anuria
  • Progressively elevating renal parameters

Painful progressive swelling (PPS)

  • Russel’s > Saw scaled > pit viper
  • Local swelling, bleeding, blistering and necrosis
  • Compartment syndrome
  • Tender draining lymph nodes

Myotoxic: Sea snake

  • Muscle aches/ swelling/ involuntary contractions
  • Myoglobinuria
  • Compartment syndrome
  • Hyperkalemia and AKI

Occult snakebite

  • No history but still consider it
  • Endemic area (Krait bite)
  • Typical history healthy person , gets bitten at night, develops severe abdomen pain/around umbilicus – neuroparalytic symptoms with 4–6 hr
  • Unexplained respiratory distress with ptosis in children
  • Acute appendicitis, acute abdomen, stroke, GB syndrome, myasthenia gravis and hysteria
  • Time delayed for ASV
  • Do Atropine-Neostigmine (AN) test to rule out snake bite

For all patients

  • MLC
  • NPO
  • Close monitoring

Check clotting time – Hourly for 3 hrs and 6th hourly for remaining 24 hrs

Measure compartment pressure; if raised plan for fasciotomy after reversal of coagulopathy otherwise the patient will bleed to death.

Late onset envenomation happens after 24 hrs to 36 hrs

Local examination of bitten part

  • Look for bite mark if any
  • Swelling
  • Colour
  • Demarcation
  • Draining lymph node examination
  • Distal pulse
  • Smell of rotten fish (putrefaction)

Before removing the Tourniquet

  • Check distal pulse
  • Untie from distal one
  • The most proximal one should be removed with all precautions.
  • Be prepared to handle respiratory and circulatory collapse.
  • In case of snake envenomation, remove only after starting ASV.

Treatment: Atropine-Neostigmine (AN)

  • Atropine 0.6mg
  • Neostigmine 1.5mg

Followed by 0.5mg with atropine every 30 min for 5 doses 1, 2nd, 6th, 12th hour respectively

Stop AN dosage schedule if;

  • Patient has complete recovery
  • Patient shows side effects in the form of fasciculations or bradycardia.
  • If there is no improvement after 3 doses.

Investigations

  • Neurotoxic – ABG
  • Vasculotoxic – Sr. Fibrinogen, D-Dimer Assay, LDH, Peripheral smear
  • Myotoxic – Urine Myoglobin, CPK
  • Infection – Procalcitonin, Culture (blood, urine, wound)

Pharmacological and supportive treatment

  • Anti-Snake Venom
  • Pain – paracetamol and opioids
  • Antibiotics – amoxyclav 1.25 TDS 7 day, Metrogyl
  • Coagulopathy – clotting factors and blood products
  • HD in acute renal failure
  • Cellulitis and Compartment syndrome – surgery

Anti-snake venom (ASV)

Monovalent and polyvalent

India and many developing countries produce polyvalent ASV

  • No objective means of identify the species
  • Costly to develop ELISA testing

Guidelines for ASV

  • Indicated if signs and symptoms of envenomation are there, even before lab reports are available.
  • No absolute contraindication
  • Don’t give incomplete dose

Risk of waiting or denying ASV

  • Risk of anaphylaxis to ASV
  • Risk of presenting with fully dilated B/L pupils
  • Respiratory arrest
  • Even if the patient presents to hospital after days ASV is indicated as long as coagulopathy persist

Dose and Dosage

Route: only IV

  • Epinephrine kept ready
  • Start slowly and watch for any reaction

Dosage

Viper bites (10 – 30 vials)

  • 10 vials over 1 hr, repeat 20WBCT after 6hr; if not clotted. again 10 vials of ASV
  • Low dose continuous :10 vials over 30mins followed by 2vials every 6hrs (in 100ml NS infusion) till clotting time(CT) normalise or for 3 days
  • High dose intermittent: 10 vials bolus followed by 6 vials 6th hrly till CT normal

For neuroparalytic snakebite

  • 10 vials stat as infusion over 30 min followed by 2nd dose of 10 vials after 1hr if no improvement within 1st

Initial dose exception for ASV

  • 30 vials over 1hr given in case of life saving surgery and need of reversal of coagulopathy after a panel discussion.
Bind with circulating venom moleculeReversal of necrotic action on tissue
Prevents patient condition from worseningReverse or prevent local swelling
Reverse renal failure
Reverse coagulopathy: Do that after poison neutralised by ASV

ASV reactions are straightforward to manage if

  1. Identified early (20 min)
  2. Treated immediately
  3. Treated with the drug of choice
  • (0.01mg/Kg) or 0.5mgIM adrenaline 1:1000 (1 or 2 dose)
  • Chlorpheniramine Maleate (CPM) 10mg (0.2mg/Kg) IV
  1. The correct mode of administration of the drug is used
  2. Correct reassessment period is used
  • Restart ASV after 15 min.

Response to ASV

  • Patient feels better
  • Spontaneous bleeding stops within 15 – 30 mins
  • 20WBCT restore in 3-9Hrs
  • In shocked patient: BP increases within 30 mins and arrhythmias settles
  • Neurotoxic symptoms: cobra envenomation improves within 30mins but not Krait
  • Active haemolysis and rhabdomyolysis ceases within few hours

Complications

Airway management in neurotoxic

  • Use of adjunct airways, LMA, definitive airway

Vasculotoxic

  • Coagulopathy not reversed by ASV
  • Needs FFP, cryoprecipitate
  • PRBC in case of haemorrhagic shock.

Venom-induced thrombin

  • Heparin is ineffective against it and may cause bleeding so never to be used in cases of snake-bite.

Vascular puncturing

  • Avoid repeated venous puncture; secure indwelling cath
  • Avoid arterial puncture

Acute renal failure

ARF can occur with Russel’s viper envenomation

Contributors

  • Intravascular hemolysis
  • DIC
  • Direct nephrotoxicity
  • Rhabdomyolysis

Forced alkaline diuresis may be tried in early stages; if fails, and in cases of late presentation, initiate HD.

Indications for dialysis

  1. Absolute value of
  • Blood urea >130 mg/dl (BUN 100 mg/dl),
  • Creatinine > 4mg/dl
  • daily rise in blood urea 30 mg/dL (BUN > 15),
  • Creatinine > 1 mg/dL,
  • Potassium > 1 mEq/L and
  • fall in bicarbonate >2 mmol/L
  1. Fluid overload leading to pulmonary oedema
  2. Hyperkalaemia (>7 or hyperkalaemic ECG changes)
  3. Unresponsive to conservative management.
  4. Uremic complications
  • Encephalopathy,
  • Nausea, vomiting, hiccups, fetor,drowsiness, confusion, coma, flapping tremor, muscle twitching, convulsions, pericardial friction rub, signs of fluid overload.

Complications Pregnant Women

  • Breast feeding encouraged
  • Snake bite may cause abortion
  • Snake venom/ASV crossing placenta is unclear
  • No dose adjustment of ASV in pregnant mother/ lactating mother/ childrens
  • No dose adjustment for repeat snake envenomation.

Discharge and follow-up

  • If no signs of envenomation in observation after 24 hr
  • If clinically stable discharge the patient after 48hrs in case of administration of ASV
  • Educate the patient about recurrence of symptoms and serum sickness
  • CPM 2mg 6th hourly for 5 days (if fails 1-2days)
  • Prednisolone 5mg 6th hourly for 5 days.

Dr Ramu

Dr. Ramu. V
Emergency Department

Journals

Kauvery Hospital
Find Doctor
Book Appointment