Emergency Medicine

196 Toxinology Emergencies

Spider Bites

The majority of spider bites are associated with local symptoms of pain and
erythema. Certain species are associated with significant envenomation, and
may be fatal.

DIAGNOSIS

1 Latrodectus species includes the red-back (Australia), the black widow

(America), and the katipo (New Zealand) spiders. Envenomation is by the

female. Clinical features of latrodectism include:

(i) Local pain, erythema, sweating, lymphadenopathy and

piloerection.

(ii) Systemic features such as headache, nausea, vomiting, abdominal

pain, generalized sweating and hypotension.

2 Over 40 species of funnel-web spider occur in Australia, with the most

significant envenomation by the male Sydney funnel-web spider. Clinical

features of funnel-web spider envenomation include:

(i) Severe localized pain, with erythema.

(ii) Generalized muscle fasciculations, nausea, vomiting, abdominal

pain, sweating, lacrimation and salivation.

(iii) Initial tachycardia and hypertension progressing to hypotension,

pulmonary oedema and finally convulsions and coma.

3 Base the diagnosis on history and clinical examination, as no laboratory

tests are helpful.

4 Perform an ECG and request a CXR if funnel-web spider bite is suspected.

MANAGEMENT

1 Apply a pressure-immobilization bandage immediately after a funnel-web

spider bite to retard the spread of the venom. Never use this in red-back

spider envenomation.

2 Otherwise, give general first-aid treatment by applying ice or heat and giving

oral analgesia as symptomatic relief.

3 Observe all patients in a monitored resuscitation area, assess and secure the

airway, and administer oxygen. Gain i.v. access only if antivenom is

indicated.

4 Antivenom administration:

(i) Red-back spider antivenom

(a) administer red-back spider antivenom to patients with

clinical manifestations of systemic toxicity or severe

uncontrolled local symptoms

(b) give one to two vials (500–1000 units) red-back spider

antivenom i.m.