Prehospital Care
Pressure immobilization of the bitten limb is not recommended due to the slow and non–life-threatening progression of symptoms. Pressure dressings may also exacerbate pain in the affected area.
Ice packs to the bite site may be helpful.
Analgesia should be provided in accordance with local protocols.
Do not administer antivenom in the field, owing to the risk of a severe allergic reaction.
Collection of the spider, if it is safe to do so without endangering providers, may aid its proper identification at the emergency department. Digital photography may be a safer way to aid in identification without handling a potentially venomous spider.
Emergency Department Care
The cornerstone of treatment of any redback envenomation is aggressive pain control; in severe cases, sedation may be necessary. There are no data to suggest superiority of any specific analgesic. Oral or parenteral NSAIDs, acetaminophen, or opioids are reasonable depending on the degree of pain. Benzodiazepines may be used for sedation if needed.
In patients with severe symptoms and signs of severe envenomation, redback spider antivenom is often given. A large amount of anecdotal and observational evidence [10, 5, 14] suggests antivenom is rapidly effective in reducing pain and systemic symptoms, although two randomized control trials (RCTs) do not show benefit over analgesia alone. A small RCT of 24 patients suggests that antivenom reduced pain more rapidly than analgesics alone but no difference in overall pain reduction and clinical outcome was noted. [15] A more recent RCT of 224 patients did not show any significant reduction in pain or systemic symptoms with antivenom administration, although a trend toward more rapid pain relief was noted. [16]
There is some controversy regarding these results, [17] however, as the treatment effect appears to be much smaller than previous experience, with most patients not experiencing pain relief at 4 hours. Consultation with a toxicologist is recommended if treatment with antivenom is being considered.
Intravenous calcium does not appear to be effective [18] and is not recommended.
If compartment syndrome due to redback spider envenomation is suspected, antivenom administration and direct measurement of intracompartmental pressure is recommended. Although compartment syndrome suspected to be caused by Latrodectus envenomation has been reported, [19] it is exceedingly rare. Prophylactic fasciotomy or fasciotomy based on clinical diagnosis of compartment syndrome should not be performed. If the compartment pressure is elevated, it should be rechecked after administration of antivenom before surgical intervention is considered.
Inpatient Care
Hospitalization is generally not required, after a period of observation, for patients whose symptoms have been alleviated with antivenom or are easily controlled with oral analgesics. Patients requiring large doses of opioid analgesics or who require sedation for symptomatic control should be hospitalized. [4] Hospitalization is also recommended in the following situations:
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Pregnant women
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Severely symptomatic children
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Elderly patients with significant comorbidities
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Patients who develop anaphylaxis to antivenom
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Patients with complications of envenomation
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Patients with hemodynamic instability
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Patients with uncontrolled hypertension
Consultations
The local poison control center should be consulted for spider identification and management of severe envenomations.
Consultation with a toxicologist is recommended in severe cases or in cases in which antivenom is being administered.
A surgeon may be consulted if compartment syndrome is suspected due to persistently elevated compartment pressures after administration of antivenom.
Complications
Antivenom-associated complications are anaphylaxis and serum sickness.
Anaphylaxis (type I hypersensitivity reaction) is characterized by urticaria, wheezing, and circulatory collapse. The risk of allergic reaction in patients receiving redback antivenom is 0.5% and is higher in patients with prior exposure to horse serum proteins or history of reactive airway disease. Anaphylaxis is treated with epinephrine, corticosteroids, antihistamines, intravenous fluids, and ventilatory support in the usual medical fashion.
Serum sickness (type III hypersensitivity reaction) is characterized by fever, urticaria, pruritus, nephritis, and arthritis. This condition occurs in 1.4% of patients receiving antivenom and is self-limiting. Treatment is usually supportive, but severe cases may be treated with systemic steroids and occasionally plasmapheresis.
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Female redback spider showing a distinctive red stripe over the abdomen. Image courtesy of John Paterson.
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Female redback spider with egg sacs. Image courtesy of John Paterson.
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Female redback spider. Image courtesy of John Paterson.
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Female redback spider. Image courtesy of John Paterson.
