Bamboo Snake Bite with Defibrination By Dr. Wong Oi Fung

Case History 5/F Attended A&E of TMH at 22:13 on 7/9/2004 Bamboo snake bite over dorsum of right foot at 21:45 on 7/9/2004 Vital signs: pulse 110/min; afebrile; GCS 15/15 Cat. 3 Disposal: admitted into pediatric ward for further management

Progress Initial assessment: Alert and conscious 2 small fang marks over dorsum of right foot No obvious swelling over other parts of lower limb Circulation and pulse--->normal Other systems--->normal

Progress…….. Initial investigation: CBP, L/RFT--> normal INR--> 1.1 Fibrinogen-->low D-dimer-->high Cardiac enzyme--> normal ECG-->no arrhythmia

Progress…….. Treatment: Antivenom Tetanus booster One dose given ( in view of rapid progression of local reaction) Tetanus booster Antibiotics (Cloxacillin, Claforan, Flaygl)

Progress…….. Outcome of initial treatment Significant swelling over right lower limb from toe to thigh noticed ??Pulses of dorsalis pedis and popliteal artery were negative Capillary refill ~ 1 sec Orthopedic surgeon consulted and suggested for conservative treatment

Progress…….. Further Investigation USG of right lower limb done: femoral and popliteal veins patent no intraluminal filling defect no fluid collection

Progress……... Transferred to PICU for close monitoring (11to 16/9/2004) Developed prolonged INR >4.5 Given repeated doses of antivenom and FFP First 2 doses from Shanghai institute; last dose from Thai Red Cross INR return to 1.2 on 14/9/2004 Discharged on 18/9/2004 Defaulted WFU on 24/9/2004

Progress of blood result and Therapy given

Discussion

Discussion Why the patient developed prolonged defibrination?? ?? Highly potent venom of the snake ?? High venom load per body mass ratio ?? Administration of coagulation factors for the unneutralized venom produced more degradation products, which are also anticoagulant ?? Antivenom from Shanghai institute was not potent enough

Discussion General information for snake bite: ~3000 species of snake found worldwide ~15 % considered to be dangerous to humans 14 common venomous species in Hong Kong White-lipped pit viper/ bamboo snake is the commonest species involved ~95% Often occurs in summer and autumn

White-lipped pit viper snake (Trimeresurus albolabris) General information: vipers are venomous snake generally short with thick body 2 subfamilies : typical vipers ( Viperinae) e.g. Russell’s viper pit vipers ( Crotalinae) e.g White-lipped pit viper

Descriptions of Bamboo Snake Length-->15 to 25 inches; max. 36 inches Female >male First upper lip shield fused with nasal shield White lateral line in males only Upper lip is pale green, yellow or white Body is green Iris are yellows Tail is dark red

Clinical Features for bamboo snake envenomation Degree of illness : >20% are dry bite Amount of venom injected Size of snake Mechanical efficiency in which the bite occurred ( e.g. both fangs penetrated the skin, repeated strikes) **repeated bites do NOT result in a depletion of venom stores.** Primary effect--->coagulopathy, thrombocytopenia, hypotension and local swelling

Venom properties Chemically complex mixtures of proteins ranging from 6 to 100KD Highly stable, resistant to temperature changes, drying and drugs 80 to 90 % of viper venom and 25 to 70% of elapid venom consists of enzymes e.g. phospholipase A. damages mitochondria, red blood cells, leucocytes, platelets, peripheral nerve endings, muscle, vascular endothelium, produces presynaptic neurotoxic activity, opiate-like sedative effect, autopharmacological release of histamine

Viper venoms Causes haemostatic defects by Venom procoagulant enzymes activate the blood clotting cascade at various sites Thrombin-like fibrinogenases remove fibrinopeptides from fibrinogen directly Activate endogenous plasminogen Inhibit platelet aggregation Combination of consumptive coagulopathy, defibrination, thrombocytopenia, vessel damage result in massively incontinent bleeding

Clinical Features for bamboo snake envenomation Local effect: Immediate severe pain, erythema and swelling Tissue necrosis due to proteolytic enzymes and phospholipases A more likely to develop in fingers and toes due to poor systemic absorption Blistering eruption presence of blister more likely to lead to necrosis or secondary infection Local infection of wound

Clinical Feature for bamboo snake envenomation Systemic effect: Haematological: Disseminated intravascular coagulation DIC due to the disorder of platelet aggregation and coagulation-fibrinolysis system Increased fibrin degradation product (FDP), increased APTT and PT, thrombocytopenia Systemic bleeding or local bleeding

Clinical Feature for bamboo snake envenomation Musculoskeletal: Rhabdomyolysis ( Russell’s Viper ) Compartment syndrome (rare after viper bite) Cadiovascular: Hypotension Arrhythmia due to myocardial toxicity Respiratory: Not characteristic of viper envenomation May occurred after Russell’s viper bite

Clinical Feature for bamboo snake envenomation Neurological: Cerebral hemorrhage Endocrine: Sheehan’s syndrome (anterior pituitary gland haemorrhage) in Russell’s viper bite GI: Nausea, vomiting and abdominal pain Renal: Acute renal failure; hyperkalaemia Other: e.g. anaphylaxis

Management in AED Physical Examination: Local signs: Systemic signs: fang marks, swelling, ecchymosis, blister, bleeding, skin necrosis, sign of compartment syndrome, regional lymphadenopathy Systemic signs: severe coagulopathy e.g. gum bleeding, epistaxis, haematuria, GIB hypotension paralysis

Management in AED Investigation: Blood testes: CBP, L/RFT, Clotting profile, muscle enzyme, Cross-match Urinalysis for haemoglobin/myoglobin ECG +/- CXR +/-FVC if available

Management in AED Release bandage for examination Analgesic Ideally pressure dressing should NOT be removed until: patient is at a medical facility resuscitation equipment is at bedside antivenom therapy has begun if systemic envenomation present Analgesic Aspirin and NSAID is CONTRAINDICATED Wound management Tetanus prophylaxis, antibiotic +/- debridment

Management in AED Close monitoring: Any patient who has been bitten by a proven or suspected venomous viper should be admitted into hospital or stay in observation ward for close monitoring for at least 12 hours Repeat the measurements of extent of swelling and ecchymosis Close monitor distal circulation Repeat CBP, RFT and clotting profile every 6 hours( avoid arterial puncture) Urine output+/- cardiac monitoring

Management……. Administration of FFP, platelet count if indication Renal replacement therapy Ventilation support

Assessment of Severity Envenomation for Viperidae Degree Clinical features Treatment No envenomation Asymptomatic Fang marks, but no local or systemic features after 6 hours from time of accident Observe for 12 hours (from time of accident) in Observation Ward. Baseline investigations. Mild Fang marks, pain, swelling less than 10cm on presentation and no significant progression after 6-12 hrs. No significant systemic symptoms. Observe for 24 hours. Baseline investigations. Repeat test 4-6 hours later if evidence of progress. Moderate Fang marks, moderate pain and swelling more than 10cm in first hour. May have petechiae or ecchymosis of bite area. Occasional minor systemic symptoms. Admit into hospital for close observation and supportive treatment. May need Antivenin treatment. Severe Marked progressive swelling and pain. Early ecchymosis and blistering. Systemic symptoms and coagulation defects. Admit into hospital for observation and treatment, preferably in ICU. Need Antivenin Tx.

Antivenom therapy Indications: Severe local envenomation Systemic Toxicity Coagulopathy Rhabdomyolysis Neurotoxicity **Antivenom can reverse systemic envenomation even after several hours after bite but is NOT effective for local envenomation unless given within several hours after bite**

Administration of Antivenom From Thai Red Cross or Shanghai institute Dilute before infusion Slow rate Preferably in ICU for close monitoring

Response to antivenom Often marked symptomatic improvement soon after administration Spontaneous systemic bleeding usually stops within 15 to 30 min Restoration of blood coagulability within 6 hours Recurrence of systemic envenomation may be due to the continuing absorption of venom form the injection site Half-life of antivenoms range from 26 to 95 hours

References Dr. WS Ng. COC guidelines for Management of snake bites (revised September 2000) Gold, BarryS.; Dart, Richard C.; Barish, Robert A. Current Concepts: Bites of Venomous Snakes. The New England Journal of Medicine. Vol. 347(5), August 2002, 347 to 356 Poisindex Management : Asian Snakes-Viperidae Oxford Textbook of Medicine 4th edition Vol. 1 pp923 to 936

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