Snake Bite-2.pdf

SNAKE BITE:
CLINICAL PRESENTATION AND
MANAGEMENT
Prof. GARBATI, MA
Infectious Diseases
UMTH, Maiduguri, Borno State
FACULTY OF INTERNAL MEDICINE
NPMCN GENERAL MEDICINE UPDATE COURSE, JULY 2022

Introduction
• Snakebite:
• More than 5 million snakebites
• 2.5 million envenomations
• Deaths - 81,000 to 138,000.
• Most occur in developing countries with poorly developed health reporting
systems.
• Regions with the highest incidence:
• Southeast and South Asia
• sub-Saharan Africa
• Latin America
• Many have limited access to health care.
WHO, 2017. Warrell Lancet 2010; Kasturiratne et al, 2008
7/29/2022 NPMCN_GM_UPDATE COURSE 2022 2

Introduction cont’d
• WHO designated snakebite as an NTD in 2017
• Snakebites affect poorer populations in rural areas.
• Common patterns of bites:
• to the arm, foot, ankle, or lower leg.
• on the head or trunk.
• The risk of snakebite also increases during the rainy season and after
floods.
WHO 2017; Bawaskar, Lancet 2019; Hunter et al, Lancet 2019;

Introduction cont’d
• Nigeria:
• Incidence - 20,000 cases of snakebite
• Mortality - 2,000 deaths occur each year
• Amputations - 1,700-2,000
• High incidence States– Adamawa, Bauchi, Benue, Borno, Enugu, Gombe, Kebbi, Kogi, Nassarawa, Oyo,
Plateau and Taraba.
• Common families of venomous snakes:
• Viperidae
• Elapidae
• Colubridae
• Actraspididae or Stiletto snakes
• Most important snakes – carpet viper (Echis ocellatus), black-necked spitting cobra (Naja nigricollis) and
puff adder (Bitis arietans).
• Habib et al, 2001

Composition of snake venom
VENOM PROPERTIES
• Snake venoms have wide variations in composition, potency, and sites of
action.
• Snake venom is a complex mixture of toxins and comprise 50–200
components distributed in dominant and secondary families.
Enzymes
• phospholipase A 2( Lecithinase), 5’nucleotidase, collaginase, L-aminoacid
oxidase, protinases, hyaluronidase, Ach, Phospholipase-b (ellipdae),
Endopeptidases, kininogenase, factor-X, prothrombin activating enzyme
(viper).
Warrell, 2012

Composition of snake venom 2
Non Enzyme Peptides:
• α- bungarotoxin, β- bungarotoxin, Crotamine, Cardiotoxin.
• Peptide - Pyroglutamyl peptide Nucleoside-Adenine, Guanine,
Inosine. Lipid-Phospholipid, Cholestrol Amine-Histamine, Serotonin,
Spermin
• Metal-Cu, Zn, Ni, Mg.

Pathogenesis
• Venoms exert a wide range of toxic activities in the body.
• Elapid venoms, and some viperid venoms, induce neuromuscular paralysis.
• Most viperid venoms, and some elapid venoms, inflict prominent local
tissue damage.
• Viperid venoms cause systemic haemorrhage, which, together with
increased vascular permeability, can lead to cardiovascular shock.
• Viperid and some elapid and some colubroid venoms act at various levels
of the coagulation cascade and on platelets, thereby affecting haemostasis.
• Some venoms cause rhabdomyolysis.
• Acute kidney injury can result from a multifactorial pathogenesis.

Pathophysiology
• Cytotoxins act on tissue at the site of the bite or on tissues that directly
absorbs the venom.
• Neurotoxins act on nervous system.
• Myotoxins targets skeletal muscles
• Hemotoxins act on the blood coagulation system and may cause bleeding.
• Cardiotoxins act on heart tissue.

Pathophysiology cont’d
• The spectrum of clinical features depends on components
and physiologic sites of action for snake venom:
• Locally acting toxins
• Swelling, blistering, ecchymosis, tissue necrosis, and pain
• Local effects are minimal or absent after bites of many elapid
snakes
• However, other elapid snakes can cause serious tissue necrosis (eg,
some African and Asian cobras)

• Systemically acting toxins
• Targets nervous system, skeletal muscles, heart, circulatory system and the
kidneys:
• Neurotoxins:
• target the neuromuscular junction (NMJ) presynaptically, postsynaptically, or
at both sites.
• Presynaptic – PLA2 and damage the terminal axon at the NMJ.
• This type of paralysis is not reversible with antivenom or anticholinesterase and may take days to
weeks for recovery of function.
• Postsynaptic – peptides which target the acetylcholine receptor on the
muscle endplate, blocking response to acetylcholine.
• This type of paralysis can sometimes be fully reversed with antivenom, or the neuromuscular block
overcome with anticholinesterases (eg, neostigmine).
Ranawaka UK, 2013

• Myotoxins –may act either systemically or locally.
• Rhabdomyolysis which occurs from enzymatic tissue damage adjacent to the bite wound (sea
snakes, some kraits, rattlesnakes, and some vipers).
• Secondary hyperkalemia and AKI
• Cardiotoxins – usually due to:
• Hemorrhage or hypovolemia.
• Less commonly, angiotensin-converting enzyme inhibitors and natriuretic peptides.
• Nephrotoxic – may occur due to:
• direct action of some venoms (especially following bites by vipers).
• AKI can also occur as a result of hypotension, coagulopathy or rhabdomyolysis.

Systemic hemostasis toxins
• Interference with blood clotting and results in consumptive coagulopathy
and hemorrhage.
• Usually reversed by timely administration of antivenom.
• There may be clotting and thrombosis resulting in DVT, PE and cerebral
infarction.
• Vascular toxicity due to damage to blood vessels
• Toxins targeting the coagulation cascade include factor X, IX, and V
activators.
• Toxins inhibiting or stimulating platelet activation.
• The hemorrhagins target blood vessel walls.

Clinical Manifestations
History
• Where and when the bite occurred
• A description of the snake
• How the bite occurred and whether there was more than one bite
• Any signs or symptoms and the timing of onset, some may be non-specific
• Initial treatment and first aid that was provided
• Any recent ethanol or recreational drug use
• Past medical history

Physical examination
• Frequent measurement of vital signs.
• Monitoring for ptosis and partial ophthalmoplegia (neurotoxic snakes)
or persistent oozing from any wounds or gums (venom-induced
coagulopathy).
• Monitor urine output and quality.
• Wound site
• Presence of fang marks
• Local evidence of envenomation.
• Repeated examinations.
• Examine regional lymph nodes.

Systemic examination
Cardiovascular
• Tachycardia and findings of shock, including hypotension and/or poor
tissue perfusion:
• prolonged capillary refill time, altered mental status, and decreased urine
output.
Tissue and muscle toxicity
• Muscle pain on palpation or with muscle use, muscle weakness, and
dark urine may indicate the presence of rhabdomyolysis.
• Look out for compartment syndrome – repeated compartment
measurements maybe required.

Systemic examination – Neurotoxicity
• Ptosis
• Ophthalmoplegia (partial or
complete)
• Pupillary dilation (often
unresponsive to light)
• Poor facial tone
• Limited mouth opening or
tongue extrusion
• Drooling
• Limb weakness or flaccid
paralysis
• Gait disturbance
• Decreased or absent reflexes
• Cranial nerve effects are
generally observed first.
• Frequent assessment of the
patients’ airway and breathing,

Asymptomatic (dry bite)
• A snake bite victim can present without any symptoms.
• Admit for observation for monitoring in case of suspected neurotoxic
bites.
• In regions with neurotoxic snakes, observe victims for up to 24 hours
post-bite.
• Bites that will result in coagulopathy usually manifest within 12 hours
after envenomation.
• Do not hasten discharge from the emergency.

Nonvenomous Snakebite
• A nonvenomous (nonpoisonous) snake bite should be distinguished
from a dry bite.
• A dry bite is a bite by a venomous snake that does not inject any
venom.
• Bites assumed to be nonvenomous need to be evaluated as they can
lead to significant tissue damage or infections.

Clinical effects of snake venoms.
A B
C D
E F
G
7/29/2022 Images courtesy of D.A.W., University of Oxford, UK. 20

Investigations
Coagulopathy
• Complete blood count with platelets
• Prothrombin time (PT)/International normalized ratio (INR) and activated partial
thromboplastin time (aPTT)
• Fibrinogen
• Fibrinogen and fibrin degradation products or D-dimer
• The 20 minute whole blood clotting test (20WBCT) - using a clean glass tube.
• Sensitivity was only 40 percent
• specificity of 100 percent in this study.
Sano-Martins IS et al. Toxicon 1994. Isbister GK et al. QJM 2013.

Investigations cont’d
Rhabdomyolysis — can be identified with the following tests:
• Rapid urine dipstick for RBCs
• Urine for myoglobin
• Microscopic hematuria
• Serum creatine kinase
• Serum electrolytes, calcium, phosphate, uric acid, blood urea
nitrogen, and creatinine
• 12-lead electrocardiogram

Pre-hospital Care
• The first priority is scene safety.
• Prevent creating additional victims.
• Do not insist on catching the snake.
• Killed snakes can still bite and inject venom.
• Obtain a photograph of the snake, if feasible to identify the
specie of snake.

Initial evaluation
Shock
• Hypovolemia from hemorrhage secondary to coagulopathy, fluid shift into
the bitten limb, and/or direct venom effects.
• Treat with rapid infusion of crystalloid solution or blood or vasoactive
medications.
• Monitor central venous pressure to avoid fluid overload.
Coma
• Patient may be comatous unable to give a history.
• Support airway, breathing, and circulation
• Exclude hypoglycemia
• May require neuroimaging.

20 Minute whole-blood clothing test
• A 20min bedside whole-blood clothing test (20WBCT) can indicate the presence
of a coagulopathy.
• Add 2mls of venous blood, into a clean, dry, glass bottle or vial and allow to stand
undisturbed for 20mins at room temperature and is then inverted.
• The presence of a clot, renders the test negative, whereas if the blood remains
liquid, the test result is positive for coagulopathy, therefore, the need for
antivenom treatment.
• Avoid IM injections
• Manage pain with paracetamol or narcotic analgesics
• Avoid NSAIDS & Aspirin
• Give tetanus toxoid to all patients and antibiotics if there is secondary bacterial
infection.

Treatment
• Patients receiving antivenom require frequent monitoring
• Resuscitation equipment and medications to treat anaphylaxis should
be made available.
• Commence antivenom immediately with the early symptoms
• In Nigeria, no deaths among 400 patients with bites due to Echis spp.
compared with a historical mortality of 10 to 20 percent among
untreated patients with similar bites.
• In the United States, mortality from snakebite dropped from as high
as 36 percent to 0.06 percent following the introduction of ASV.
Abubakar IS et al, PLoS Negl Trop Dis 2010

Anti Venom Therapy
Route of administration
• The IV route of administration is preferred to intramuscular (IM)
injection
• In small children, if IV access is not possible, use intraosseous
route.
• Snake antivenom can be administered in one of two ways:
• Antivenom diluted in a compatible solution (eg, normal saline) and
infused over 30 to 60 minutes.
• Reconstituted (if required; eg, lyophilized antivenoms) and given
by slow IV injection over 10 to 20 minutes.

Anti Venom Therapy2
• Ideally administer within 4 hrs of the bite but effective if given within
24 hrs.
• In mild cases-5 vials (50 ml)
• In moderate cases-5 to 10 vials
• In severe cases-10 to 20 vials
• Additional 5 to 10 vials might be required in cases with slow
response.
• Avoid local injection of ASV.

Monitoring of patients
Response to treatment
• Administration of inadequate amounts of antivenom or use of the wrong
antivenom.
• Late administration antivenom to be effective, in advanced paralysis due to a
neurotoxic venom.
Coagulopathy
• Spontaneous bleeding ceases by about 20 minutes.
• Coagulation tests normalize by about six to eight hours.
Hypotension and cardiotoxicity
• Marked improvement should occur within 20 to 30 minutes.
Neurotoxicity
• Detectable improvement within 30 minutes.

Adjunctive therapy
• Cobra spit ophthalmia
• The venom of the spitting cobras (Naja spp.) can cause corneal damage
• Irrigate eyes with copious quantities of water or saline.
• Slit lamp examination should be performed to evaluate for corneal ulceration
• Use topical antibiotic ointment.
• Tetanus prophylaxis
• This should be considered tetanus in all cases
• Antibiotics
• To be used on case by cases basis
• Blood products
• whole blood or fresh frozen plasma (FFP) can be given to address coagulopathy.
• platelet transfusions are indicated in patients with thrombocytopenia and bleeding.
Goldman DR et al, 2010.

7/29/2022
Black-necked spitting Cobra Naja nigricollis spit resulting in blindness
NPMCN_GM_UPDATE COURSE 2022 32

Adverse reactions to antivenom
• Allergic reactions
• Early allergic reactions
• Pyrogenic reactions
• Late allergic reactions (serum sickness)
• resuscitation equipment and medications to treat anaphylaxis should be
made available.
• Rates of anaphylaxis can be as high as 80 percent
• Serum sickness can occur several days or weeks after treatment
• Symptoms include fever, chills, rash, muscle aches, joint aches, itching, and
hematuria.
Lalloo DG, 2003; Alirol E, 2010

Adverse reactions to antivenom
Seen in 20 % patients
Early anaphylactic reaction-
• Seen within 3 min to 60 min
• Urticaria, pruritus, bronchospasm, angioedema, diarrhoea,
tachycardia, fever, hypotension.
Late reactions (Serum Sickness)
• May occur 5-24 days
• Fever, itching, urticaria, nausea, vomiting, diarrhoea,
arthritis, nephritis, myoglobinuria.

PROGNOSIS
• Prognosis usually good if managed early and appropriately.
• Delayed treatment often leads to unfavorable outcomes.
• Retrospective review of cases (2007-2009) in Kaltungo General Hospital
(KGH), Gombe State.
• Overall snakebite mortality of 1.41%.
• Potential reasons of increased mortality:
• Obtaining antivenoms from the retail outlets.
• Use of insufficient amount of ASV.
• Delay in buying antivenoms because of prohibitive cost.
• Use of unreliable or fake products.
• Use of geographically inappropriate antivenoms.
Habib and Abubakar, 2011

PREVENTION OF SNAKEBITE
• Public education especially in high-risk communities.
• Using the media using radio, TV, social media, posters, and drama
performances.
• People should watch out for snakes during walking, working and
sleeping.
• Early transportation to clinics where they can receive medical care.
• People should be discouraged regarding visiting traditional therapists.

PREVENTION OF SNAKEBITE
• Avoid handling snakes..
• A US study showed that about 40% of all snake bites occur in people
that consumed alcoholic.
• Wear protective clothes in endemic areas.
• Avoid walking or putting hands in dark places.

SUMMARY
• Snakebite is one of the neglected tropical diseases
• Potentially life-threatening disease.
• High-risk groups mainly in rural communities
• Occasionally bites can be dry
• Every snake bite case should be treated as a medical emergency
• Prevention of bites should be given priority

THANK YOU
QUESTIONS AND COMMENTS ARE WELCOME

Snake Bite-2.pdf

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