Redback Spider

Redback Spider bites are the most common envenoming in Australia. Venom is from the latrodectus genus which is abundant in different countries around the world. Some of which use antivenom and some do not. This is a hot debated topic in toxicology and will shall explain further in this post.

Classically an intense pain develops 5-10 minutes after a bite, followed by sweating and piloerection on the affected limb. The pain is usually controlled by analgesia but there are a spectrum of patients who develop systemic features that can be debilitating the the use of antivenom remains controversial.

Resus
  • Redback spider envenomation is not life threatening.
Risk Assessment


Typical symptoms include:

  • Local bite site pain followed by sweating and piloerection within an hour. A puncture mark may not always be present
  • Systemic envenoming occurs in a minority causing regional and then generalised pain (classic stories of appendicitis mimics). Autonomic features include severe sweating, hypertension and tachycardia.
  • Non-specific features include a headache, nausea, vomiting and dysphoria.
  • Children may present with inconsolable crying, abdominal pain and priapism
  • Untreated symptoms usually resolve in 1-4 days with a few patients feeling unwell for unto one week

Supportive Care

  • Analgesia First aid measures including an ice pack and simple analgesia including paracetamol and ibuprofen are often effective. For those patients refractory to this oral opiates like oxycodone 0.1 mg/kg (max 10mg) every 4 hours have been effective before proceeding to IV opiates (0.1 mg/kg of morphine).
  • Antivenom maybe used in cases of severe pain refractory to opiates and severe systemic features after an informed discussion with the patient. See Controversies section.
Investigations
  • Not required
Differential Diagnosis:
  • Envenoming by cupboard or brown house spiders closely resembles a redback spider envenomation
  • Funnel-web spider envenoming should not be mistaken for a redback as these can potentially be fatal. Funnel-webs are associated with immediate pain, fang marks with characteristic sweating, agitation, piloerection, cardiovascular and neurological symptoms.
Antivenom
  • CSL Redback Spider Antivenom Used to treat moderate to sever pain and systemic symptoms. Recent literature has questioned its utility but there is also longstanding anecdotal experience in patients with severe symptoms showing some benefit. The pro’s and con’s (risk of anaphylaxis) need to be discussed with the patient before use and it would be worth discussing with your local toxicology team for their advice
Disposition
  • Envenomed patients maybe discharged when their symptoms are mild or under control
Controversies
  • The latest trial regarding antivenom administration for latrodectism (RAVE II) suggests there is no significant clinical benefit above standard analgesia for the control of pain and systemic symptoms of redback envenoming.

References and Additional Resources:

Additional Resources:

Zeff – James Hayes Fellowship teaching Spider bite

References:


toxicology library antidote 700 1

Toxicology Library

TOXINS

Dr Neil Long BMBS FACEM FRCEM FRCPC. Emergency Physician at Burnaby Hospital in Vancouver. Loves the misery of alpine climbing and working in austere environments. Supporter of FOAMed, toxicology, tropical medicine, sim and ultrasound

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