SNAKE BITE

Dr.A. Sridhar Ist year pg

Snake bite
3000 species of snakes, out of them only 10-15% of snakes are venomous 300 species are in India .INDIAN snakes ranges from Wormsnakes10cm to KING COBRA6M.

.70% bites are from non-venomous species,5O%bites by venomous species doesnt cause envenomation.{dry bites}

Important species in INDIA

Cobras(nagraj) Naja naja,N.oxiana, N.kabuthia Common krait(karayat)-Bungarus caeruleus Russells viper(kander)-Daboia russelii Saw scaled viper - Echis.carinatus(afai)

COBRA

COMMON KRAIT

RUSSELS VIPER

ECHIS CARINATUS

Poisonous Snakes
Head Triangle Fangs Present Pupils - Elliptical pupil Anal Plate - Single row Bite Mark - Fang Mark

Non Poisonous Snakes

Head - Rounded Fangs - Not present Pupils - Rounded Anal Plate - Double row Bite Mark - Row of small teeth.

 How to identify a dead snake if it is brought to the ER

Carefully handle the snake because even dead snake fangs can transmit poison Viper fangs are anterior,lengthy & loose Elapidae have short,thick anterior fangs

SNAKE VENOM
Snakes that inject venom use glands, which are actually modified salivary glands. Venom is a modified form of saliva and probably evolved to aid in chemical digestion. Varying degrees of toxicity also make it useful in killing prey.

VENOM APPARATUS
The venom glands of elapidae & viperidae are situated behind the eyes & surrounded by compressor muscles Venom duct opens withinin the sheath at the base of the fang Venom is conducted to fang tip through a canal

Venom properties
Contain 20 or more components

>90% of the dry Wt of venom is protein- in the form of enzymes,non enzymatic polypeptide toxins & non toxic proteins .
Most venoms contain L-aminoacid oxidase, phosphomono & diesterases, 5nucleotidase,DNAase,NAD-nucleosidase, phospholipaseA2 & peptidases

Contd
Phospholipase A2(lecithinase) damages mitochondria,RBCs,WBCs,platelets, peripheral nerve endings,skeletal muscles, vascular

endothelium & other membranes, produces

presynaptic neurotoxic activity & release of

histamine

Contd
Proteolytic enzymes(endopeptidases & hydrolases) are responsible for local changes in vascular permeability leading to

edema,blistering & bruising & to necrosis

Hyaluronidase promotes the spread of venom

through tissues

POLYPEPTIDE TOXINS
Postsynaptic () neurotoxins such as bungarotoxin and cobrotoxin,are bind to acetylcholine receptors at the motor endplate Presynaptic()neurotoxins such as bungarotoxin,crotoxin,& taipoxin release acetylcholine at the nerve endings at NMJs & then damage the endings,preventing furthur release of the transmitter

PHARMACOLOGY
Absorbed through the blood & lymphatics Spitting cobra- venom can be absorbed through the intact cornea Most venoms are concentrated in the kidneys & some are eliminated in urine Bungarotoxin are tightly bound at the NMJ Most venoms donot cross the blood brain barrier

Clinical features
When venom not injected : Anxious people-hyperventilation-stiffness, tetany of hands and feet, dizzines Vasovagal shock-few First aid measures-constriction bands-pain, swelling, congestion

When venom injected

Nausea & vomiting are common early symptoms

of systemic envenoming
Early syncope,vomiting,colic,diarrhoea, angioedema & wheezing may occur Local pain & bleeding from the fang punctures,swelling, bruising ,lymphangitis & regional lymphadenopathy

Bites by cobra
More of neurotoxic ,local effects

Neurotoxic Ptosis Ciliary mussle paralysis Partial/total opthalmoplegia Broken neck sign

Bulbar palsy
Locked-in syndrome

Bites by kraits
Most poisonous snake in india Local urticaria-rare Delayed neuropathy of affected limb-rare Bulbar palsy Respiratory paralysis Asphyxic cardiac arrest No local pain or tissue damage

Bites by Viper
cytotoxic & hemotoxic Severe local effects Rapid devlopment of DIC Immediate shock Neuroparalysis-ptosis,respiratory paralysis Sheehans syndrome

 Pain & tenderness in regional lymph nodes with bruising of overlying tissues & lymphangitic lines Bruising ,blistering & necrosis may appear in the next few days Compartment syn may develop

Contd
Haemostatic abnormalities are characteristic of envenoming by viperidae Hypotension & shock are common Myocardial involvement may be present Early collapse after bites has been attributed to coronary & pulmonary thromboembolism

Contd
Oliguria & loin pain indicate renal ischaemia

Generalised rhabdomyolysis
myoglobinuria Renal failure is a common mode of death Sawscaled viper doesnt causeneurological or renal complications

ecchymosis

Necrosis

Bite marks

Bites by Sea snake

Both myotoxic&haematotoxic Trismus is common Between 30mins to 3.5hrs,generalized aching,stiffness & tenderness of the muscles. Later there is generalized flaccid paralysis

Contd
Myoglobinuria appears 3 to 8hrs after the bite Myoglobin & potassium released from damaged skeletal muscle can cause renal failure

Investigations
CBC RFT Coagulation studies Blood grouping & cross matching Sr.electrolytes Urinalysis

Contd
20 min whole blood clotting test Sr.creatine kinase,myoglobin & potassium levels ECG-sinus bradycardia,ST-T changes, various degrees of AV block & hyperkalaemic changes Immunodiagnosis

MANAGMENT
Do it R.I.G.H.T. It consists of the following: R. = Reassure the patient. I = Immobilise in the same way as a fractured limb. Use bandages or cloth to hold the splints, Do not apply ligatures G. H. = Get to Hospital Immediately.. T= Tell the doctor of any systemic symptoms such as ptosis that manifest on the way to hospital.

Antivenom ,antivenin,antivenene & antisnake serum

POLYVALENT ANTIVENINS MONOVALENT ANTIVENINS: Highly effective against a particular species & are available only in some countries based on the epidemicity of specific snakes

POLYVALENT ANTIVENIN
Manufactured by hyper immunizing horses against venoms of four standard snakes Cobra (naja naja) Krait (B.caerulus) Russels viper(V.russelli) Saw scaled viper(Echis carinatus)

 Lyophilised form:stored in a cool dark place & may last for 5 years Liquid form:has to be stored at 4c with much shorter life span,2Yrs Each 1ml of reconstituted serum neutralise 0.6 mg of naja naja 0.45 mg of Bungarus caerulus 0.6 mg of V.russelli 0.45 mg of Echis carinatus

Approximate initial dose

Common krait-100ml Russellviper- 100ml Indian cobra-100ml Echis spp-100ml Given at the rate of 2ml/min IV push or as iv

infusion with 5ml/kg of isotonic fluid ,all ASV has2be administered in 1hr

 ROUTE OF ADMINISTRATION--IV
WHY NOT IM?

WHEN TO GIVE IM?

Indications for antivenom

Local envenoming 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)

Indications for antivenom

Local envenoming Rapid extension of swelling (for example beyond the wrist or ankle within a few hours of bites on the hands or feet) Development of an enlarged tender lymph node draining the bitten limb

Indications for antivenom

Systemic envenoming Haemostatic abnormalities: spontaneous systemic bleeding (clinical), coagulopathy (20WBCT or other laboratory) or thrombocytopenia (<100 x109/litre) (laboratory)

Indications for antivenom

Neurotoxic signs: ptosis, external ophthalmoplegia, paralysis etc (clinical) Cardiovascular abnormalities: hypotension, shock, cardiac arrhythmia (clinical), abnormal ECG

Indications for antivenom

Acute renal failure: oliguria/anuria (clinical), rising blood creatinine/ urea (Haemoglobin-/myoglobin-uria:) dark brown urine (clinical), urine dipsticks, other evidence of intravascular haemolysis or generalised rhabdomyolysis (muscle aches and pains, hyperkalaemia)

Treatment of antivenom reactions

Early (anaphylactic) reactions,occur within 10180 min Adrenaline 0.5 mg ,1:1000,IM . If hypotension,severe bronchospasm or

laryngeal edema give 0.5 mg,1:10000of

adrenaline IV

Contd
A histamine anti H1 blocker-chlorpheniramine maleate-10 mg IV Pyrogenic reactions-occurs 1-2hrs after treatment, give antipyretics Late reactions-occur 1-12daysafter treatment respond to CPM-2 mg, 6 hrly or oral

prednisolone-5 mg 6 hrly

Contd
If patient goes for airway obstruction & respiratory paralysis MECHANICALVENTILATION

Supportive treatment
First do NEOSTIGMINE TEST IF VICTIM RESPONDS CONTINUE WITH 0.5 mg of neostigmine IM ,half hourly plus 0.6mg of atropine IV over an 8hr period by continuous infusion If there is no improvement after 1hr neostigmine should be stopped

Contd
Hypotension & shock-a plasma expander, dopamine. Oliguria & renal failure-fluids,diuretics, dopamine-if no response,fluid restriction, dialysis Local infection-TT,antibiotics

Contd
Intracompartmental syn & fasciotomy Haemostatic disturbances-FFP,fresh whole blood,cryoprecipitates

Treatment of snake venom ophthalmiatopical antimicrobial,0.1% adrenaline relieves pain