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wikitox:problems_for_discussion_4_snakes

Problems for Discussion - 4 - Snakes

BROWN SNAKES

Objectives

  • Detail the clinical effects of Brown snake envenomation.
  • Understand the differences in the toxicity of different species of Pseudonaja .
  • Detail the appropriate first aid for snake bites.
  • Understand the indications for Brown snake antivenom.
  • Understand how to monitor victims of Brown snake bite and how long asymptomatic patients should be observed in hospital.
  • Understand the pros and cons of pre-treatment prior to administering antivenom.
  • Understand when fresh frozen plasma should be administered for coagulopathy following brown snake envenomation.

Problem 1

A 36-year old male felt a sharp ‘slapping feeling’ on his right foot while passing urine around the back of a sheering shed in Western Australia. He did not see a snake and did not think of snakebite. Ten minutes later, while helping a friend load a motorcycle onto the back of a trailer, he abruptly felt unwell with nausea, dizziness, weakness and a mild headache. He collapsed to the ground but does not think he lost consciousness. His wife thought he might have bitten by a snake and put a pressure immobilisation bandage (PIB) on his leg.

He arrived at a peripheral urban hospital by ambulance 70 minutes later. He appeared pale and sweaty. His vital signs were normal and there was no evidence of abnormal bleeding or neurotoxicity. The PIB was reinforced and IV access obtained.

Blood test results showed INR > 10, APTT > 180, Fibrinogen < 0.3, CK 275, normal renal function and normal full blood picture (Hb 148, platelets 178). Venom detection kit (VDK) undertaken on urine was strongly positive for Brown snake. The hospital has limited after hours laboratory support and 5 ampoules of Brown snake antivenom.

  1. What is your risk assessment
  2. Is antivenom indicated and if so, how much should be administered?
  3. The patient is one and a half-hours drive from the nearest tertiary referral centre. Should the patient be moved or should antivenom be brought to the hospital?
    Repeat bloods four hours after being bitten showed INR > 10, APTT > 180, Fibrinogen < 0.3, CK 248, > normal renal function, Hb 135 and platelets of 132. LDH was 1620 U/L.
  4. Why is the LDH elevated?
  5. Is antivenom indicated and if so, how much should be administered?
  6. When should the pressure immobilisation bandage be removed?
  7. What are the indications for administering fresh frozen plasma?
    Eight hours after being bitten bloods showed INR > 10, APTT > 180, Fibrinogen < 0.3, CK 160, normal renal function, Hb 111 and platelets of 90. LDH was 1500 U/L.
  8. Is antivenom indicated and if so, how much should be administered?
    Twelve hours after being bitten blood tests showed INR 2.4, APTT 48, fibrinogen 0.4, CK 121, normal renal function, Hb 101 and platelets 99.
  9. Is antivenom indicated and if so, how much should be administered?
  10. When should investigations be repeated?

Problem 2

A 25 year old male snake handler was bitten on the left middle finger by a captive Ingram’s Brown snake during routine cage maintenance. He had a history of three previous snake bites; twice by Death Adders, once requiring antivenom and a Tiger snake. After being bitten the patient flicked the snake onto the floor, sucked the bite site and recaptured the snake. He then felt nauseated and generally unwell with a severe headache. A compression bandage was applied and the limb splinted.

On arrival at hospital thirty minutes later he had photophobia, nausea and a headache. Blood tests 1 hour after being bitten showed INR > 10, APTT > 160, creatinine 100, Hb 147 and platelets of 112.

  1. What should the patient have done differently immediately following being bitten?
  2. What other tests would you undertake?
  3. Is antivenom indicated and if so, how much should be administered?
  4. If antivenom is administered should the patient be pre-treated with adrenaline, promethazine or hydrocortisone? Does the patient’s past history influence this decision? Is there any potential adverse effects that influences this decision?
    Eight hours after the bite the patient is feeling symptomatically improved. Repeat blood tests showed INR > 10, APTT > 249, Fibrinogen < 1.0, creatinine 160, Hb 141, platelets 115 and LDH 543.
  5. What are the possible causes of the elevated creatinine and how should it be treated?
  6. Is antivenom indicated and if so, how much should be administered?
    16 hours after the bite repeat blood tests showed INR 2.2, APTT 50, Fibrinogen 1.6, creatinine 150, Hb 125, platelets 138 and LDH 379.
  7. Is antivenom indicated and if so, how much should be administered?

Case adapted from Brimacombe J, Murray A. Envenomation by Ingram’s Brown snake (Pseudonaja Ingrami). Anaesth Intens Care 1995; 23: 231-233.

TAIPAN

Objectives

  • Detail the clinical effects of Taipan envenomation.
  • Appreciate the rapid time course following Taipan envenomation and the severity of effects.
  • Understand the indications for Taipan antivenom.
  • Understand how to monitor victims of Taipan snake bite and how long asymptomatic patients should be observed in hospital.
  • Understand the risk of serum sickness following antivenom administration and the potential role for prophylactic corticosteroids.

Problem 1

A peripheral hospital is expecting a herpetologist who has been bitten by a snake. The herpetologist believes he has been bitten by his Inland Taipan. There is no information about symptoms or first aid undertaken. The Hospital only has 2 ampoules of polyvalent antivenom and are seeking advice on initial management.

1. What do you advise?
2. What investigations are indicated?
3. Under what situations would you recommend the administration of polyvalent antivenom and what initial dose would you advise?

Further information is made available after the patient arrives at the hospital. The 33-year-old male herpetologist bitten by a presumed Taipan presented at 1730 hours. He was bitten on the right thumb at approximately 1700 hours and immediately applied a pressure immobilisation bandage but did not splint the limb. The patient complained of pain in the right axilla. He felt flushed and complained of mildly heavy eyes.

There were no objective neurological signs and the patient’s physical examination was normal. Coagulation profile showed INR of 1.0 and APTT of 27. Fibrinogen is not yet available. The VDK was strongly positive for taipan at the bite site.

At 2030 hours the patient was asymptomatic. Repeat blood tests show an INR of 20.8 and APTT of 150 secs. There is evidence of haemolysis with bilirubin of 34. Fibrinogen is pending. CK is 134. The hospital has sourced three ampoules of taipan antivenom and six ampoules of polyvalent antivenom. A haematologist has been consulted and recommended 10 units of cryoprecipitate be administered.

4. What further clinical information would assist in this assessment?
5. Is antivenom indicated; if so how much of which one?
6. What do you think of the advice from the Haematologist?
7. At 0330 the patient remained asymptomatic Repeat blood tests showed an INR of 2.1, APTT of 15 and fibrinogen less then 0.3 g/L.
8. Is antivenom indicated?
9. The peripheral hospital is 20 minutes by road from a tertiary hospital. Should the patient have been transferred?
10. If the patient receives antivenom should prophylactic steroids be commenced?

Problem 2

A 28 yr old woman presents following a single bite to her hand from a 1.6m Taipan she had just purchased. She applied no first aid and was severely inebriated at the time of the bite. She is uncooperative, then lapses into unconsciousness.

  1. What special risks should you consider in this situation?
  2. What investigations are indicated?
  3. Is antivenom indicated when this patient first presents and prior to obtaining the results of any investigations?
  4. What further problems might you encounter?
  5. How would you manage this case?
  6. What advice should be offered to this woman on discharge?

Objectives

  • Detail the clinical effects of Tiger snake envenomation and related species.
  • Understand the differences in the toxicity of different species of Notechis, Austrelaps, Tropidechis and Hoplocephalus.
  • Understand the indications for Tiger snake antivenom.
  • Understand how to monitor victims of Tiger snake bite.
  • Understand the pros and cons of pre-treatment prior to administering antivenom.
  • Understand when fresh frozen plasma should be administered for coagulopathy following Tiger snake envenomation.

Problem 1

A 44 year old male was bitten by a snake on his finger at approximately midnight. The patient breeds tiger snakes. The patient apparently collapsed shortly after being bitten but the exact details of the collapse are not known. A pressure immobilisation bandage was placed on the arm and the patient was transported to hospital by ambulance, arriving one hour after being bitten. On arrival at hospital he is drowsy and is mildly disorientated. Vital signs are normal. There are multiple petechiae on the face and limbs.

The patient received antivenom for a Tiger snake bite last year. The hospital has a total of 4 ampoules of tiger snake monovalent antivenom.

  1. What specific findings on examination are important?
  2. What initial treatment do you recommend?
  3. What investigations are indicated?
    Blood tests show an INR > 10 and APTT > 150. CK is 195 and electrolytes are normal. The bite site swab is positive for tiger snake.
  4. Is antivenom indicated and how much should be administered?
  5. Should promethazine, hydrocortisone or adrenaline be administered prior to antivenom?
  6. How long should the pressure immobilisation bandage remain in place for?
  7. When should blood tests be repeated?

Problem 2

A 44 year old man presents following a bite from a captive rough scaled snake, while working in a venom collection facility. Shortly after the bite, despite immediate application of appropriate first aid, he developed a runny nose, red rash, then chest tightness. These are now resolving, but he has a headache and nausea.

  1. What special risks should you consider in this situation?
  2. What further problems might you encounter?
  3. What are the possible causes of the rash and chest tightness?
  4. How would you manage this case?
  5. Is antivenom indicated now; if so how much would you administer?

MULGA, COLLETT'S BUTLER'S MULGA AND EASTERN SMALL EYED SNAKES

Objectives

  • Understand the distribution of these snakes
  • Compare the toxicity of Mulga, Collett’s and Butler’s Mulga snakes with the other members of the genus Pseudechis.
  • List the investigations required for monitoring a bitten patient.
  • Detail the indications for antivenom treatment.

Problem 1

A 24 year old amateur snake handler was bitten at the base of the right thumb as he was dropping a Mulga snake into a bag. Immediately after the bite he applied a tight tourniquet around the right arm. He arrived at hospital 30 minutes after the bite complaining of severe pain in the right hand. He appeared pale and apprehensive. The right hand was swollen and tense and the skin was bluish white in colour. Two deep 3 mm long lacerations were present on the palmar aspect at the base of the thumb. The past history is significant for previous bites by P. australis but he had not received antivenom before.

  1. Outline your initial management?
  2. What investigations are indicated?
  3. Is antivenom indicated?
    Over the next few hours the pain and swelling extended up the length of the right arm. The only abnormal results were proteinuria, an APPT of 45 and INR of 1.7.
  4. What management would you advise now?
  5. What monitoring is required?

Problem 2

A 64-year-old snake handler was bitten on the right wrist by a Collett’s snake while cleaning out its cage. Immediately after the bite he placed an arterial tourniquet to his right upper arm. A pressure immobilisation bandage was then applied and he was transported to hospital by ambulance. His only symptoms were nausea. In the past he has been envenomated by Tiger and Brown snakes and received antivenom to both without developing an allergic reaction.

On examination he is awake and alert, with stable vital signs. He has no ptosis. Puncture marks are noted to the anterior and posterior aspects of the wrist; they are not bleeding. The right hand is cold and there is no capillary return.

He is given 10 mg of intravenous metoclopramide and develops an urticarial rash within 5 minutes.

  1. What is your initial management?
  2. Is there an indication for antivenom; if not what further information is required?
    The initial blood results 45 minutes after the bite are:
    • Na 144
    • K 3.9
    • Cl 106
    • CO2 22
    • Urea 8.4
    • Creat 104
    • CK 186
    • WCC 6.8
    • Hb 167
    • Plt 205
    • APTT 73
    • INR 1.2
    • Fibrinogen 364
  3. What would you do now?
  4. Is antivenom indicated?
    The patients nausea is controlled with a combination of antiemetics and his main complaint is of pain in the right forearm. On examination he is haemodynamically stable. The right forearm appears swollen and erythaematous but is neurovascularly intact. For the first time since arriving at hospital he has passed 200 ml of urine which is described as “chocolate coloured”. Repeat blood tests 17 and half-hours after the bite are:
    • Na 144
    • K 4.9
    • Cl 109
    • CO2 18
    • Urea 13.9
    • Creat 255
    • CK 7929
    • WCC 49.5
    • Hb 153
    • Plt 57
    • APTT 29
    • INR 1.2
    • Fibrinogen 385
  5. What would you do now?
  6. Is antivenom indicated?
    Over the following 5 hours the patient becomes anuric and complains of abdominal pain. Repeat blood test 23 hours after the bite are:
    • Na 139
    • K 5.3
    • Cl 106
    • CO2 18
    • Urea 16.5
    • Creat 310
    • CK 9737
    • WCC 53.1
    • Hb 139
    • Plt 40
    • APTT 30
    • INR 1.3
    • Fibrinogen 469
  7. What would you do now?
  8. Is antivenom indicated?
  9. Why have only snake handlers been reported to be envenomated by Collett’s snakes?

DEATH ADDERS

Objectives

  • To understand the clinical effects of Death Adder envenomation.
  • Describe the management of Death Adder envenomation.
  • Discuss therapies other than antivenom and when these may be indicated.
  • Comment on the prognosis of treated Death Adder envenomation and the response to antivenom.

Problem 1

A 35 year old bushwalker is flown to hospital by rescue helicopter from a valley in far North Queensland. He gives a history of stepping on a snake that he described as a Death adder. The snake bit him on the dorsum of his right foot penetrating the cloth material of the upper sole of his shoe.

A pressure immobilisation bandage and splint were applied and the patient’s companion left him to climb to higher ground so that he was within mobile phone coverage to call for assistance. Over the next hour the patient developed nausea and a headache. The bite site was painful and swollen but not bleeding.

On returning after two hours the patient’s companion noted that his eyelids were drooping. On arrival of a rescue team by helicopter three hours after the bite the patient described blurring of vision and diplopia. On examination ptosis and opthalmoplegia were noted. Limb strength appeared normal.

  1. The rescue team includes an Emergency Physician. They have brought two vials of polyvalent antivenom with them. Flight time to the nearest major hospital is 25 minutes. Should they administer antivenom prior to transport?
  2. What additional information would assist in answering this question?
    On arrival at hospital the patient still had ptosis and opthalmoplegia and described heaviness of the limbs and difficulty breathing. On examination 4/5 power is demonstrated in limb muscles. Oxygen saturation on room air is 97%. Forced vital capacity is 2 litres. The following results were obtained:
    • Na 141
    • K 3.9
    • Cl 106
    • CO2 26
    • Urea 5.5
    • Creat 87
    • CK 155
    • WCC 11.5
    • Hb 148
    • Plt 356
    • APTT 30
    • INR 1.0
    • Fibrinogen 338
      The pressure immobilisation bandage and splint are still in place. The hospital has a snake venom detection kit and polyvalent antivenom but no Death Adder antivenom. Death Adder antivenom can be obtained from another hospital about 30 minutes away by road.
  3. Should the antivenom detection kit be utilised?
  4. What treatment options are there and which do you recommend?
  5. When should the splint and pressure immobilisation bandage be removed?
  6. What is this patient’s prognosis?

Problem 2

You are contacted for medical advice by a hospital in Alice Springs. They have a patient, an 18-year-old boy who was bitten by a snake three hours previously. One of the patient’s friends shot the snake and brought it to hospital with them. The head of the snake is difficult to identify because of the gun shot wound but the Doctor thinks it is a Death Adder. The patient is extremely anxious and is complaining pain at the bite site, and of nausea, a headache, and a sense of impending doom. The bite site shows two puncture marks but is not swollen or bleeding.

The hospital has the complete range of CLS antivenom available.

  1. What specific question do you ask?
  2. What other tests would you undertake?
  3. Is antivenom indicated?
  4. What additional treatment is indicated?
    The bite site was swabbed and the snake venom detection kit was positive in wells 4 and 7.

Biochemistry, haematology and coagulation studies are all within normal limits. Over the next hour the patient is not improving and says he feels he is “going to die” and is short of breath. An arterial blood gas shows:

  • pH 7.49
  • PO2 106
  • PCO2 28
  • HCO3 20
  1. What additional tests may assist in evaluating this patient?
  2. Is antivenom indicated and if so which one?
  3. What is the prognosis?

Problem 3

A 24 year old man presents drunk, some 4 hours after being bitten by his pet death adder. He has not used first aid. He is allergic to antivenom, he says.

  1. What problems should you be looking for?
  2. What should be done to establish if he is envenomed?
  3. Should you consider using antivenom in this case and if so, on what indications?
  4. What other actions should you consider?

BLACK SNAKES

Objectives

  • Detail the clinical effects of Black snake envenomation and related species.
  • Understand the differences in the toxicity of different species of Pseudechis and Demansia.
  • Understand the indications for Tiger snake antivenom and why this is preferable to Black snake antivenom.
  • Understand how to monitor victims of Black and Whip snake bite.

Problem 1

You are contacted by Panawonica Hospital in the Pilbara Region, Western Australia. A 58-year old prospector was bitten on the forearm by a 2 metre snake as he was sorting firewood. The snake was aggressive and required considerable effort to remove. The patient washed the bite site with bourbon and presented to the local hospital 40 minutes after the bite without any pressure bandage or attempt to immobilise. He complains of considerable pain and mild swelling at the bite site, abdominal pain and headache. He has vomited several times.

Examination shows fang marks and mild swelling on the forearm. Vital signs are normal. There is no evidence of abnormal bleeding at the bite site, gingiva, or venepuncture site. There is no evidence of neurotoxicity. There are no laboratory facilities in Panawonica and they only have 2 ampoules of polyvalent antivenom. The doctor calls for advice.

  1. What venomous snakes are present in this region?
  2. What snakes could produce this clinical picture?
  3. What management do you advise?
    The patient was retrieved to Port Hedland. At Pt Hedland there are 10, 2 and 2 ampoules of Brown, Black and Death adder monovalent antivenom respectively.
    On arrival at Pt Hedland the patient still complained of headache and abdominal pain, plus pain at the bite site. Renal function was normal, CK 1586 IU/L, INR 2.1, APTT 48 seconds and fibrinogen 4.2. Full blood picture was normal. Bite site venom detection was not attempted. VDK undertaken on urine was faintly positive in black snake and brown snake wells at 13 minutes.
  4. How do you interpret the VDK result?
  5. What management do you advise?
  6. What are the indications for antivenom administration?
  7. If indicated what antivenom do you advise and how should be given?

EXOTIC SNAKEBITES

Objectives

  • To understand the spectrum of envenoming by these snakes and apply this to the diagnosis and treatment of envenoming.
  • Understand the natural evolution of envenoming and how this may influence diagnosis.
  • Understand the appropriate type and scheduling of investigations.
  • Understand the appropriate choice and use of antivenom, and potential adjunctive treatments.

Problem 1

A 42 year old man presents following a bite from a forest cobra at the zoo he was working at. This is not his first bite and he has had antivenom previously, though no adverse reaction is recorded.

  1. What should you expect if he is envenomed?
  2. What should be done to establish the extent of the problem?
  3. What is the appropriate treatment?
  4. What problems might be encountered?

Problem 2

A 21 year old man is bitten on the lip by a western diamondback rattlesnake while he is cleaning its cage at a zoo. He has not been bitten by a snake before.

  1. What special risks should you consider in this situation?
  2. What further problems might you encounter?
  3. How would you manage this case?
  4. What advice should be offered to this man on discharge?

Problem 3

A 5 year old child is brought in comatose following a bite from a 50cm long snake thought to be a python by his parents. The snake had been purchased in a pub. The snake is identified by an expert as a Russell’s Viper.

  1. What special risks should you consider in this situation?
  2. What further problems might you encounter?
  3. How would you manage this case?
  4. What other actions should you consider in this case?
wikitox/problems_for_discussion_4_snakes.txt · Last modified: 2018/09/01 09:01 (external edit)