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Envenomation

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Envenomation

Management

First aid

  • aim is to delay systemic absorption of venom
  • venom moves in superficial lymphatics and capillaries
  • for all rapid acting venoms use bandage and splint method. Firm bandage is applied over bitten area and up the limb which is then splinted. Patient is not allowed to move and should be carried to ambulance/hospital as muscle activity speeds systemic absorption. For bites on trunk firm pressure should be applied over the bitten area and a firm bandage applied
  • there is no role for arterial tourniquets
  • localization of venom by bandage may lead to its local detoxification
  • for venoms which produce late life-threatening effects (eg stonefish and red back spider) bandage and splint techniques are not indicated and may increase pain
  • pain from stonefish, fortescue and bull rout envenomation responds to warm water and Portugese man of war to ice.
  • application of vinegar is advised for box jellyfish envenomation as this paralyses the stinging apparatus

Emergency room treatment

  • depends on what first aid measures have been taken and on the patients symptoms
  • history of headache, abdominal pain, nausea and vomiting or abnormal coagulation accurately predict envenomation in children who have a presumptive diagnosis of envenomation
  • if initial management is observation this should continue for 6h in adults and 24h in children. In adults virtually all serious envenomations produce symptoms within 4h
  • if the patient has received no first aid immediate treatment is only indicated if there are signs of significant envenomation: wound should be bandaged, definitive treatment given and then the bandage removed. For those with no or only minor symptoms initial plan should be to observe
  • patients treated with bandage and splint: remove bandage and observe unless there are signs of significant envenomation in which case give definitive treatment and then remove bandage
  • those treated with arterial tourniquet:
    - if there are no symptoms remove tourniquet and observe;
    - minor symptoms: prepare for definitive treatment, remove tourniquet and depending on result either treat or simply observe;
    - features of significant envenomation: definitive treatment prior to removing tourniquet

Anaphylaxis

  • in snake handlers, zoo keepers and people who have previously been bitten anaphylaxis to venom may occur. This may confuse and complicate diagnosis and management. The same patients are also at greater risk of anaphylaxis in response to anti-venom
  • Portugese man of war , bee, wasp and jumper ant stings more likely to kill through allergic than toxic means
  • severe hypotension in snake bite due to Australian snakes should lead to anaphylaxis being considered
  • use of mast cell tryptase assays may confirm the diagnosis of anaphylaxis in reactions to the venoms of snakes and Hymenoptera

Antivenom

Indications

Indicated only if there is evidence of significant envenomation but do not wait for life-threatening symptoms

Pretreatment

  • appears to reduce incidence of adverse reactions to anti-venoms although there is no controlled data to support this
  • current recommendation is to give parenteral anti-histamine and IM epinephrine (0.5 mg) prior to anti-venom. Latter is controversial, particularly because of risk of intracerebral haemorrhage. However there is no increase in ICH in those given IM epinephrine compared to those who are not.

Administration

  • dose governed by the amount of venom injected and not the size of the patient. Dose should not be reduced in children
  • administer in at least 500 ml saline by slow infusion. Patient should be carefully monitored during infusion

Assessing effects

  • should result in prompt improvement
  • continued deterioration or failure to improve may result from inadequate dose or wrong antivenom

Adjunctive treatment

  • 5 day course of steroids after polyvalent or large doses of antivenom are recommended by some to prevent serum sickness. Incidence of delayed reaction to Australian antivenoms is about 5%. There are no controlled trials of the use of such adjunctive treatment

Management of envenomation by specific species

Funnel web spiders

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  • largely confined to east coast of Australia
  • bites often associated with envenomation
  • envenomation results in release of endogenous transmitters which produce an "autonomic storm" leading to salivation, hypertension, tachycardia, gastric dilatation, pulmonary oedema, muscle spasms, metabolic and respiratory acidosis and possibly raised intracranial pressure
  • symptomatic treatment includes muscle paralysis, artificial ventilation, vasodilators, high levels of PEEP to control pulmonary oedema and volume replacement with colloid
  • antivenom rapidly reverses all symptoms and appears to be effective in all species

Red back spider

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  • bites usually to trunk rather than limbs
  • female is poisonous
  • symptoms related to release of acetyl choline and catecholamines from autonomic terminals
  • severe pain within minutes of bite. Spreads across body. Associated with localized sweating which also spreads across the body
  • other clinical features include: lymphadenopathy, shivering, headache, nausea and vomiting, pyrexia, hypertension, tachycardia, muscle spasms and paralysis
  • ice-packs may produce symptomatic relief
  • IM antivenom 500 U repeated after 2h if there is no improvement. Can be given IV in severe cases. Pretreatment indicated in patients allergic to horse serum and if antivenom is given IV
  • diazepam may help control muscle spasms. Effective up to 2 weeks after envenomation

Ticks

  • found in scrub and bush country in east-coast regions of Australia
  • tick buries bytosome into host tissues
  • as well as being vectors of disease ticks may produed symptoms via acquired allergies to secretions or a potent neurotoxin in saliva
  • clinical features: ataxia, progressive motor weakness leading to paralysis. May be mistaken for Guillain Barre syndrome or polio. Other features include difficulty reading, toxic myocarditis, rhabdomyolysis and lymphadenopathy
  • search carefully for ticks in all cases presenting with muscle weakness. Ticks should be removed by dousing with kerosene and then prising the tick free with curved forceps
  • antitoxin for significant paralysis. Give 2 ampoules in severe cases

Jellyfish

  • Pelagia noctiluca (little mauve stinger) and Physalia physalis (Portugese man of war) produce marked local pain and redness and may produce anaphylaxis. Pain and redness may be relieved by cold compress
  • Irekandji (Carukia barnsei) produces pain, nausea, vomiting, profuse sweating and backache. Vinegar for first aid and treatment with analgesia
  • Box jellyfish is most dangerous jellyfish in the world. Envenomation causes severe pain and skin whealing which leads to necrosis. Rapidly followed by hypotension and paralysis. Treatment is by dousing with vinegar and applying a bandage and splint over the envenomated area. Mechanical ventilation until antivenom can be administered. Plasma expanders and analgesia may be required. Cliropsolins quadrigatis envenomation produces similar but less severe effects

Blue-ringed octopus

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  • bite may be totally painless
  • ± cerebellar signs in mild cases
  • usual presentation is paralysis from tetradotoxin. Treatment is bandage and splint first aid and mechanical ventilation. There is no antivenom

Stonefish

  • characteristically envenomate through dorsal fins when trod on
  • stings extremely painful
  • ± muscle paralysis, weakness, cardiovascular collapse and skin necrosis
  • first aid: apply warm-hot water to decrease pain.
  • better analgesia can be obtained with injection of local anaesthesia. Regional block should be considered in multiple stings
  • debride puncture wound
  • antivenom unless minor discomfort is the sole feature. One ampoule for every two punctures up to 3 ampoules

Bees and ants

  • most life-threatening feature is anaphylaxis
  • massive stinging may result in similar clinical picture
  • other major complication is upper airway obstruction following airway sting

Snakes

Known effects of snake venoms in Australia:

  • muscular paralysis
  • coagulopathy and DIC
  • rhabdomyolysis
  • hypotension
  • All of the above should be treated along conventional lines and antivenom should be administered
  • brown snake also has a nephrotoxin and renal failure in the absence of rhabdomyolysis may occur
  • local tissue damage: symptomatic. Necrotic tissue should be debrided but tissue necrosis is less common with Australian snakes than species such as rattlesnakes and cobras
  • sudden collapse and death may occur in brown snake bite
White-lipped viper (Bamboo snake)

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Further reading

Fisher MM. Envenomation. In Oh TE (ed), Intensive Care Manual, 4th Ed., Butterworth Heinemann, Oxford, 1997, pp 646-50


© Charles Gomersall December 1999

 

©Charles Gomersall, April, 2014 unless otherwise stated. The author, editor and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from the use of this webpage.
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