Question 41#

Brown snake envenoming is the most common cause of death from snake bite in Australia. Severe envenoming results in venom-induced consumptive coagulopathy (VICC). The laboratory characteristics of VICC are all of the following EXCEPT:

A. Elevated or unrecordable international normalized ratio (INR)

Answer: B: Brown snake venom contains potent procoagulants, cardiotoxins and presynaptic neurotoxins. VICC is the hallmark of brown snake envenoming and can cause death due to uncontrolled haemorrhage. The onset is usually early after the bite and presents as bleeding from the gums and venepuncture sites, as well as intracerebral haemorrhage. The INR and D-dimer are elevated in VICC, whereas fibrinogen is consumed and its levels are almost undetectable.

In addition to VICC envenomed patients may have thrombocytopenia and microangiopathic haemolytic anaemia. Apart from brown snake envenoming, tiger snake and taipan envenoming are also likely to cause VICC.

Reference:

1. Murray L, Daly F, Little M, et al. Toxicology handbook. 2nd ed. Brown snake. Sydney: Churchill Livingstone Elsevier; 2011. p. 433–4.

Question 42#

Regarding clinical effects due to envenoming by Australian elapidae snakes, which ONE of the following statements is FALSE?

A. Tiger snake envenoming causes consumptive coagulopathy, neurotoxicity and rhabdomyolysis

Answer: D: Important species of black snakes such as the mulga snake cause myotoxin-induced rhabdomyolysis leading to generalized myalgia, weakness, elevated creatine kinase (CK), myoglobinuria and renal failure. Although venom of these snakes contains anticoagulants (not procoagulants), these anticoagulants do not generally cause significant clinical problems or abnormalities of the coagulation profile. Bites from red-bellied and blue-bellied black snakes rarely cause significant systemic envenoming features. Minor myolysis may occur but features of paralysis or coagulopathy do not.

Clinical features due to neurotoxicity and rhabdomyolysis are uncommon with brown snake envenoming, whereas these features are more prominent with taipan and tiger snake envenoming. Tiger snake envenoming causes VICC similar to brown snake envenoming. In addition to procoagulants, the venom also contains pre- and postsynaptic neurotoxins and myolysins. In contrast to brown snake envenoming, neurotoxicity and rhabdomyolysis are prominent features and usually develop over the ensuing hours.

References:

1. Murray L, Daly F, Little M, et al. Toxicology handbook. 2nd ed. Brown snake. Sydney: Churchill Livingstone Elsevier; 2011. p. 433–4.
2. Murray L, Daly F, Little M, et al. Toxicology handbook. 2nd ed. Black snake. Sydney: Churchill Livingstone Elsevier; 2011. p. 430–2.
3. Murray L, Daly F, Little M, et al. Toxicology handbook. 2nd ed. Tiger snake. Sydney: Churchill Livingstone Elsevier; 2011. p. 439–42.
4. Murray L, Daly F, Little M, et al. Toxicology handbook. 2nd ed. Taipan. Sydney: Churchill Livingstone Elsevier; 2011. p. 442–5. 

Question 43#

Regarding the choice of antivenom to be given in the treatment of envenoming due to snake bite, which ONE of the following statements is TRUE?

A. Protein loads given in single doses of polyvalent and monovalent antivenom are equal

Answer: B: In an envenomed patient the choice of antivenom depends on patient’s clinical symptoms, the laboratory results, the SVDK test result (which indicates the genus of the snake involved), and knowledge of distribution of snakes in the geographical location.

Monovalent antivenom is the preferred type of antivenom as it significantly reduces the protein load given to a patient. A single ampoule of polyvalent antivenom contains one ampoule from each of the monovalent antivenom available. The indications for use of polyvalent antivenom include the following:

• When there are clinical features of severe life-threatening envenoming and the SVDK result is not immediately available.
• Mixing three or more monovalent antivenom is required to cover all the possible snakes found in the geographical location.
• SVDK cannot be done.

The rate of anaphylaxis and anaphylactoid reactions is 1% for monovalent antivenom and 5% for polyvalent antivenom. As this prevalence is low, prophylactic treatment is not required irrespective of the type of antivenom used.

There is a risk of developing serum sickness from both types of antivenom.

Reference:

1. Murray L, Daly F, Little M, et al. Toxicology handbook. 2nd ed. Approach to snakebite. Sydney: Churchill Livingstone Elsevier; 2011. p. 36–43.

Question 44#

All of the following statements are TRUE regarding redback spider antivenom EXCEPT:

A. Antivenom can be recommenced with caution after an acute allergic reaction once control of clinical manifestations has been achieved

Answer: B: Redback spider antivenom is indicated in cases of redback spider bite with refractory local pain or with features of systemic envenoming. These features include:

• Initial local pain becoming regional or generalized
• Autonomic dysfunction with local or generalized sweating
• Tachycardia
• Mild hypertension

The antivenom can also be trialed in patients who had a suspected redback spider bite when that diagnosis is uncertain. Pregnancy is not a contraindication. Children receive the same dose as adults as reversal of venom is the principle of treatment. The antivenom dose does not depend on the age of the patient. However, when using antivenom on children the volume needed to dilute may need to be adjusted. Antivenom can be given intravenously as a diluted preparation with close monitoring. It is equally effective intramuscularly when given undiluted.

Acute allergic reactions are uncommon and occur more frequently with intravenous than intramuscular administration. When such a reaction does occur the antivenom infusion should immediately be stopped, oxygen and fluids given, and if needed, IM adrenaline administered. The antivenom infusion may be recommenced cautiously when the clinical manifestations are controlled. Rarely, it might be necessary to administer an ongoing adrenaline infusion to complete the antivenom administration.

References:

1. Murray L, Daly F, Little M, et al. Toxicology handbook. 2nd ed. Redback spider. Sydney: Churchill Livingstone Elsevier; 2011. p. 459–60.
2. Murray L, Daly F, Little M, et al. Toxicology handbook. 2nd ed. CSL redback spider antivenom. Sydney: Churchill Livingstone Elsevier; 2011: 486–8.

Question 45#

Funnel-web spider bite is potentially lethal. All of the following are features of funnel-web spider bite EXCEPT:

A. Local erythema and swelling

Answer: A: Patients often give a history of witnessing a painful bite by a big black spider with large fangs. Local erythema and swelling are not features of funnel-web spider bite. Funnel-web spider bite is potentially life threatening. Severe envenoming features rapidly develop within 30 minutes to two hours. Clinical features include:

• General: agitation, vomiting, headache and abdominal pain
• Autonomic: sweating, salivation
• Cardiovascular: tachy- or bradycardia, hypo- or hypertension, pulmonary oedema
• Neurological: paraesthesia, fasciculation, muscle spasm, coma

Young children may present with inconsolable crying and vomiting.

Reference:

1. Murray L, Daly F, Little M, et al. Toxicology handbook. 2nd ed. Funnel-web (big black) spider. Sydney: Churchill Livingstone Elsevier; 2011. p. 461–2.