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HKEC Inter-department Toxicology Interest Group Meeting April 9, 2010

HKEC Inter-department Toxicology Interest Group Meeting April 9, 2010. Snake Bite. By Dr. Rex PK Lam FHKAM (Emergency Medicine), HKCEM. Snake bite is NOT uncommon in HK. Dr. Rex Lam PYNEH Tox Team 2010. Don’t forget the Snake shops!. Dr. Rex Lam PYNEH Tox Team 2010.

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HKEC Inter-department Toxicology Interest Group Meeting April 9, 2010

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  1. HKEC Inter-department Toxicology Interest Group Meeting April 9, 2010 Snake Bite By Dr. Rex PK Lam FHKAM (Emergency Medicine), HKCEM

  2. Snake bite is NOT uncommon in HK Dr. Rex Lam PYNEH Tox Team 2010

  3. Don’t forget the Snake shops! Dr. Rex Lam PYNEH Tox Team 2010

  4. And … some people keep snake at home Dr. Rex Lam PYNEH Tox Team 2010

  5. Know your enemies! • NOT all snakes are venomous • 4 families of venomous snake in HK • Bamboo snake is the most common offender (95%) Dr. Rex Lam PYNEH Tox Team 2010

  6. Envenomation • 20% dry bite (Fang mark ≠ envenomation) • envenomation – local vs systemic • Analphylaxis • Consider each case individually • Different venom amount delivery, compositions, body reaction • Risk of mis-identifcation Dr. Rex Lam PYNEH Tox Team 2010

  7. Characteristics of venomous snake • Triangular head (venomous gland) • Fang • Pupils (vertical elliptical in viperids, round in elapidae) • Facial pit in pit viper • Brightly colour rings encircle the body (not head or tail) • Subcaudal scale (single in krait, paired in pit-vipers) Dr. Rex Lam PYNEH Tox Team 2010

  8. The Big 4s + 1 • Viperidae 蝮蛇科 • Bamboo snake • Elapidae 眼鏡蛇科 • Cobra • Krait • Colubridae 游蛇科 • Hydrophiidae 海蛇科 • Imported snake : Russel’s viper Dr. Rex Lam PYNEH Tox Team 2010

  9. Viper -Bamboo snake (Trimeresurus albolabris)

  10. Viper – Bamboo snake • Most common offender > 95% • Local – pain, swelling +/- brusing • Systemic – thrombin-like effect -> coagulopathy Dr. Rex Lam PYNEH Tox Team 2010

  11. Elapidae – Cobra (Naja atra) Local tissue necrosis Dr. Rex Lam PYNEH Tox Team 2010 Neurotoxicity

  12. Elapidae – Banded Krait (Bungarus fasciatus) Dr. Rex Lam PYNEH Tox Team 2010

  13. Elapidae – Many-banded krait(Bungarus multicinctus) Dr. Rex Lam PYNEH Tox Team 2010

  14. Krait envenomation • local – minimal reaction • Systemic – paralysis • Ptosis, neck flexor, limbs, respiratory paralysis • Bungarotoxins • α Bungarotoxin – Antagonistic effect to Ach receptors NMJ • Β Bungarotoxin – inhibit pre-synatpic Ach release Dr. Rex Lam PYNEH Tox Team 2010

  15. Russell’s viper (Vipera russelli) • Causing most death in SE Asia • Local • swelling, pain • Systemic • Coagulopathy • Rhabdomyolysis • Renal failure Dr. Rex Lam PYNEH Tox Team 2010

  16. Envenomation syndrome SnakeBite Severe local tissue reaction Minimal/mild local tissue reaction Renal failure rhabdomyolysis Coagulopathy Neuropathy Neuropathy Viper – Bamboo snake Cobra Krait Russell’s viper Dr. Rex Lam PYNEH Tox Team 2010

  17. General approach to snake bite • Stay Clam ! • Supportive treatment – ABC • Assessment of the extent and severity envenomation Dr. Rex Lam PYNEH Tox Team 2010

  18. Snake bite assessment • Focused history • Time, place, event • Allergy • First aid measures in the field • Snake type identification • Patient’s description • Envenomation features • Dead specimen • Dead snake can bite! Dr. Rex Lam PYNEH Tox Team 2010

  19. Dr. Rex Lam PYNEH Tox Team 2010

  20. Baseline investigation • CBP • APTT, PT, INR, WBCT • Fibrinogen, FDP • RFT • CK • ECG • Urine x myoglobulin • +/- CXR Dr. Rex Lam PYNEH Tox Team 2010

  21. Continuous monitoring

  22. Principle of antivenom use (1) • Need risk-benefit assessment • Use early if indicated • more specific better • Same dose in children (different dilution) • Skin test NOT needed • Premedication • piriton + hydrocortisone +/- adrenaline • Need close monitoring • Dose depends on clinical response Dr. Rex Lam PYNEH Tox Team 2010

  23. Principle of antivenom use (2) • Horse sera products • Major concerns • Early : anaphylaxis • Late: serum sickness syndrome Dr. Rex Lam PYNEH Tox Team 2010

  24. Principle of antivenom use (2) • Close monitor area – R-room / ICU • Resucitation personnel and equipment immediately available • At least 2 large bore IV • Pre-treatment • iv piriton • Iv hydrocortisone • +/- SC adrenaline Dr. Rex Lam PYNEH Tox Team 2010

  25. Never forget! • Supportive case • Wound dressing and monitoring • ATT • Analgesic • Antibiotics • Observe for at least 12 hrs even for asymptomatic patient Dr. Rex Lam PYNEH Tox Team 2009

  26. Why prophylactic antibiotics? • A cross-sectional study on stray snake • 32 Chinese Cobras and 7 Bamboo snakes • Wide range of bacteria: • Gram-neg: Morganella morganii, Aeromons hydrohilia and Proteus • Gram-pos: Enterococcus faecalis • Anaerobes: clostridia Levofloxacin + augmentin Dr. Rex Lam PYNEH Tox Team 2010

  27. Multidisciplinary care • ICU care – severe neurotoxicity, ARF… • Surgical intervention • Debridement • Compartment syndrome • Medical input – severe coagulopathy… • Psychiatrist - PTSD … Dr. Rex Lam PYNEH Tox Team 2010

  28. Real Case Scenarios Dr. Rex Lam PYNEH Tox Team 2010

  29. Case 1 • F/78 • Phx HT • 16:50 Left M/F bitten by a green snake in Cheung Chau • 17:49 attended SJH for marked L hand swelling • 19:21 arrived PYNEH AED (Casevac A) with the dead snake Dr. Rex Lam PYNEH Tox Team 2010

  30. On arrival • GCS 15/15 • BP 167/77 p 76 • SaO2 98% • Temp 37.2oC • Left M/F markedly swollen, swelling spread to left forearm > 10cm What is the snake? What are the major concerns ? Dr. Rex Lam PYNEH Tox Team 2010

  31. Viper -Bamboo snake (Trimeresurus albolabris)

  32. Yes, it is a Bamboo snake • Major concerns • Envenomation • Local tissue cytotoxic effect • swelling, pain, blistering, bruise, compartment syndrome • Systemic • Thrombin-like effect -> coagulopathy, bleeding tendency • Nausea, vomiting, dizziness, hypotension • Anaphylaxis Dr. Rex Lam PYNEH Tox Team 2010

  33. Investigations • CBP • WBC 11.1 • Hb 12.5 • Plt 68 (baseline 273) • Clotting APTT/PT/INR normal • RFT normal • CK normal Would you give antivenom? Dr. Rex Lam PYNEH Tox Team 2010

  34. Antivenom is indicated because: • Local envenomation • Rapid progression • Crossed one major joint already • Systemic envenomation • thrombocytopenia What are the antivenoms available in PYNEH? Dr. Rex Lam PYNEH Tox Team 2010

  35. Agkistrodon halys Shanghai Institute of Biological Products, Ministry of Health Make up to 500ml 0.9% NS Start at 100ml/hr If no allergic reaction in the first 5-10 mins, give the whole vial over 30mins Dr. Rex Lam PYNEH Tox Team 2010

  36. Refrigerator Dr. Rex Lam PYNEH Tox Team 2010

  37. Green Pit Viper Thai Red Cross 2-4 vial Need reconstitution in sterile water included in the package Slow IV infusion ∼ 2ml/min Dr. Rex Lam PYNEH Tox Team 2010

  38. Progress (1) • NS q4h • Tramadol IMI in SJH • Bandage and ice • IV piriton + IV hydrocortisone • 3 vials of Green Pit Viper given in AED • ATT and wound dressing • Admitted to EMW • Started A&C Dr. Rex Lam PYNEH Tox Team 2010

  39. Progress in EMW (2) • Given 2 more doses of antivenom in EMW • Left UL swelling decreased gradually • Clotting profile remained normal • No allergic reaction • Discharged on day 4 Dr. Rex Lam PYNEH Tox Team 2010

  40. Progress (3) • FU at AED on day 7 • Still mild swelling and hotness • Plt 191 • No rash • FU at AED on Day 11 • Swelling subsided • Case closed Dr. Rex Lam PYNEH Tox Team 2010

  41. Case 2 • M/37 GPH • 19:50 Bitten by a black-colored snake at right 4th and 5th toe • 20:02 presented to SJH for marked pain and numbness • 21:11 arrived at PYNEH AED (Casevac A) with the dead snake Dr. Rex Lam PYNEH Tox Team 2010

  42. On arrival • GCS 15/15 • BP 161/86, P 82 • SaO2 98% RA, RR 18 • Temp 36.4oC • Limb power full Dr. Rex Lam PYNEH Tox Team 2010

  43. Dr. Rex Lam PYNEH Tox Team 2010

  44. Dr. Rex Lam PYNEH Tox Team 2010

  45. What is this snake? Dr. Rex Lam PYNEH Tox Team 2010

  46. Cobra (Naja atra) Local tissue necrosis Dr. Rex Lam PYNEH Tox Team 2010 Neurotoxicity

  47. Investigations • CBP • WBC 13.0 • Hb 13.5 • Plt 262 • Clotting profile – normal • RFT normal • CPK 334 Would you give antivenom? Dr. Rex Lam PYNEH Tox Team 2010

  48. AED management • Analgesic • Tramadol, toradol in SJH • Morphine in PY • NS drip • Antivenom: 2 vials of Naja Naja with iv piriton and hydrocortisone as pre-med • Wound dressing and ATT • Admit ICU Dr. Rex Lam PYNEH Tox Team 2010

  49. Progress (1) • No ptosis nor neurological symptoms • Swelling slightly improved • Given augmentin and ciprofloxacin • D/C from ICU 22 hr post-bite to EMW • D/C from EMW on day 3 Dr. Rex Lam PYNEH Tox Team 2010

  50. Progress (2) • FU AED on day 10 • Increase pain and swelling since D/C • Not taking antibiotics • Patient refused in-patient care • FU AED on day 15 • Wound tissue necrosis Dr. Rex Lam PYNEH Tox Team 2010

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