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Emergency Medicine > ENVIRONMENTAL
Spider Envenomation, Widow
Article Last Updated: Aug 22, 2006
AUTHOR AND EDITOR INFORMATION
Section 1 of 11  
Author: Sean P Bush, MD, FACEP, Professor of Emergency Medicine, Envenomation Specialist, Department of Emergency Medicine, Loma Linda University School of Medicine; Consulting Staff, Loma Linda University Medical Center
Sean P Bush is a member of the following medical societies: American College of Emergency Physicians, Society for Academic Emergency Medicine, and Wilderness Medical Society
Coauthor(s):
Jennifer C Smith, MD, Fellow in Envenomation Medicine, Department of Emergency Medicine, Loma Linda Medical Center
Editors: Robert Norris, MD, Chief, Associate Professor, Department of Surgery, Division of Emergency Medicine, Stanford University Medical Center; John T VanDeVoort, PharmD, ABAT, Director of Pharmacy, Sacred Heart Hospital; James S Walker, DO, Program Coordinator, Associate Professor, Department of Emergency Medicine, University of Oklahoma Health Sciences Center; John D Halamka, MD, MS, Associate Professor of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center; Chief Information Officer, CareGroup Healthcare System and Harvard Medical School; Attending Physician, Division of Emergency Medicine, Beth Israel Deaconess Medical Center; Jonathan Adler, MD, Attending Physician, Department of Emergency Medicine, Massachusetts General Hospital; Division of Emergency Medicine, Harvard Medical School
Author and Editor Disclosure
Synonyms and related keywords:
Latrodectus, black widow spider, Latrodectus mactans mactans, brown widow, Latrodectus geometricus, red-legged widow, Latrodectus bishopi, redback spider, Latrodectus hasselti, button spider, Latrodectus indistinctus, Latrodectus variolus, Latrodectus hesperus, Latrodectus mactans tredecimguttatus, Latrodectus pallidus, spider envenomation
Background
Widow spiders belong to the genus Latrodectus and include the black widow spider (Latrodectus mactans mactans) in the United States. The term widow spider is used because not all species in the genus Latrodectus are black. Other widow spiders in North America include the brown widow (Latrodectus geometricus), the red-legged widow (Latrodectus bishopi), Latrodectus variolus, and Latrodectus hesperus. The redback spider (Latrodectus hasselti) is endemic to Australia. Latrodectus mactans tredecimguttatus and Latrodectus pallidus are found in Europe and South America, and the button spider (Latrodectus indistinctus) is found in South Africa.
The adult female black widow spider is approximately 2 cm in length and shiny black with a red-orange hourglass or spot on the ventral abdomen. The male is much smaller, brown, and incapable of envenomating humans. Juvenile females are also brown but have the general body morphology of the adult. Males and juveniles have a pale hourglass shape, similar to adult females. The female sometimes eats the male during or after copulation. Webs are irregular, low-lying, and commonly seen in garages, barns, outhouses, and foliage. Other widow spiders are generally black but may have red spots, such as Latrodectus mactans tredecimguttatus, or a dorsal red stripe, such as the redback spider. Latrodectus geometricus is brown with red and yellow markings.
Pathophysiology
Alpha-latrotoxin causes the toxic effects observed in humans by opening cation channels (including calcium channels) presynaptically, causing increased release of multiple neurotransmitters. This results in excess stimulation of motor endplates with resultant clinical manifestations. Clinically, the predominant effects are neurological and autonomic, in contrast to the dermonecrotic local effects associated with spiders causing necrotic arachnidism (eg, brown spiders [Loxosceles species]).
Frequency
United States
Approximately 2500 widow spider bites were reported to the American Association of Poison Control Centers (AAPCC) in 2001, although this figure is probably conservative because of underreporting.
Mortality/Morbidity
In the United States, an average of 4 deaths per year are reported to occur as a result of spider bites. However, no deaths caused by widow spider envenomation have been reported to the AAPCC since its first annual report in 1983. Deaths after black widow spider bites were reported in 2001 and 2003 in Spain and Greece, respectively.
History
- Pain at the bite site is generally trivial and may go unnoticed. It commonly is described as a pinch or pinprick; however, infants may present with unexplained crying.
- Within about 1 hour, systemic symptoms begin and may last for a few days.
- Muscle cramping
- Cramping may occur locally, around the area bitten.
- It may extend into large muscle groups, such as the abdomen, back, chest, and thighs.
- Case reports suggest involvement of smooth muscles, such as bronchial or endometrial.
- Nausea and vomiting
- Headache
- Anxiety
Physical
- Abnormal vital signs
- Diaphoresis
- Locally, around the area bitten
- Remote from site of envenomation
- Tiny fang marks may be visible.
- Local effects are usually limited to a small circle of redness and/or induration around the immediate bite site. A central reddened fang puncture site surrounded by an area of blanching and an outer halo of redness is described as a having a target appearance.
- Abdominal rigidity may mimic an acute abdomen.
- Neurologic effects, including mild weakness, fasciculations, and ptosis, have been described.
- Latrodectus facies, characterized by spasm of facial muscles, edematous eyelids, and lacrimation may occur. This can be mistaken for an allergic reaction.
- Bronchorrhea and pulmonary edema have been described in Europe and South Africa.
Acute Coronary Syndrome
Aneurysm, Abdominal
Anxiety
Appendicitis, Acute
Back Pain, Mechanical
Bites, Insects
Caterpillar Envenomations
Centipede Envenomations
Cholecystitis and Biliary Colic
Hypocalcemia
Mesenteric Ischemia
Millipede Envenomations
Myocardial Infarction
Pregnancy, Ectopic
Scorpion Envenomations
Spider Envenomations, Brown Recluse
Spider Envenomations, Redback
Spider Envenomations, Tarantula
Lab Studies
- If the diagnosis is uncertain, laboratory studies to rule out an acute abdomen may be indicated (eg, CBC, pregnancy test).
- The serum creatine kinase (CK) and peripheral white blood cell count may be elevated.
Imaging Studies
- Consider performing an acute abdominal series or an abdominal CT scan if the diagnosis is unclear in a patient presenting with abdominal pain.
Other Tests
- Skin testing variably may predict immediate hypersensitivity to antivenom and may influence the decision regarding its administration. Antivenom-induced anaphylaxis may be more life threatening than the envenomation itself.
- Obtain an ECG, if indicated (eg, comorbidity, chest pain, severe hypertension).
Prehospital Care
- Support the airway, breathing, and circulation per ACLS protocols with oxygen, monitors, and intravenous line.
- Negative pressure venom extraction devices (eg, The Extractor - Sawyer Products) have not been evaluated for treatment of widow spider envenomation.
- Electric shock and various folk and herbal remedies lack therapeutic value and are potentially harmful.
- Do not give antivenom in the field because of the risk of severe allergic complications.
- Attempts to secure the spider may be helpful in confirming widow spider envenomation.
Emergency Department Care
- Antivenom should be given for imminent risk of severe complication of envenomation (see Complications). The risk of allergy to antivenom must be weighed against the benefit of relieving prolonged discomfort, avoiding hospitalization, and preventing complications.
- Grade 1 - Mild envenomation
- Local pain at envenomation site
- Normal vital signs
- Grade 2 - Moderate envenomation
- Muscular pain in the envenomated extremity
- Extension of muscular pain to the abdomen if bitten on a lower extremity or to the chest if envenomated on an upper extremity
- Local diaphoresis of envenomation site or involved extremity
- Normal vital signs
- Grade 3 - Severe envenomation
- Generalized muscular pain in the back, abdomen, and chest
- Diaphoresis remote from envenomation site
- Abnormal vital signs (blood pressure >140/90 mm Hg, pulse >100)
- Nausea and vomiting
- Headache
Consultations
- Local poison control centers may assist management of difficult envenomations.
- The Antivenom Index, published by the American Zoo and Aquarium Association and the American Association of Poison Control Centers, lists the locations, amounts, and various types of antivenom stores.
Most widow spider envenomations may be managed with opioid analgesics and sedative-hypnotics. Antivenom may be indicated for patients who have severe envenomations with pain refractory to these measures. Antivenom should be considered when envenomation seriously threatens pregnancy or precipitates potentially limb- or life-threatening effects (eg, severe hypertension, unstable angina, priapism, compartment syndrome). On average, antivenom administration results in resolution of most symptoms one-half hour after administration, and it has been shown to decrease the need for hospitalization. A new antivenom (Aracmyn, manufactured by Instituto Bioclon) is currently undergoing phase 2 clinical trials in the United States, but it has not yet been approved for general use. It is thought to be safer than the existing antivenom, so its indications for use may differ from the current indications. Calcium gluconate is no longer recommended for widow spider envenomation. Studies suggest benzodiazepines are more
efficacious than muscle relaxants for treatment of widow spider envenomation. Antibiotics are not indicated.
Drug Category: Analgesics
Pain control is essential to quality patient care. It ensures patient comfort and promotes pulmonary toilet. Most analgesics have sedating properties that are beneficial for patients who have sustained trauma.
| Drug Name | Morphine sulfate (Duramorph, Infumorph, Astramorph injections) |
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| Description | DOC for narcotic analgesia because of its reliable and predictable effects, safety profile, and ease of reversibility with naloxone. Morphine sulfate administered IV may be dosed in a number of ways and commonly is titrated to the desired effect. |
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| Adult Dose | 2-10 mg IV/IM; titrate to relief of pain |
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| Pediatric Dose | 0.1 mg/kg IV/IM |
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| Contraindications | Documented hypersensitivity; hypotension; potentially compromised airway with uncertain rapid airway control; hypotension; respiratory depression; constipation; urinary retention |
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| Interactions | Phenothiazines may antagonize the analgesic effects of opiate agonists; tricyclic antidepressants, MAOIs, and other CNS depressants may potentiate adverse effects of morphine when used concurrently |
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| Pregnancy | C - Safety for use during pregnancy has not been established.
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| Precautions | Avoid in hypotension, respiratory depression, nausea, emesis, constipation, and urinary retention; caution in atrial flutter and other supraventricular tachycardias; has vagolytic action and may increase ventricular response rate |
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Drug Category: Benzodiazepines
By binding to specific receptor sites, these agents appear to potentiate the effects of gamma-aminobutyrate (GABA) and to facilitate inhibitory GABA neurotransmission and other inhibitory transmitters.
| Drug Name | Lorazepam (Ativan) |
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| Description | A sedative hypnotic in the benzodiazepine class that has a short onset of effect and relatively long half-life. By increasing the action of GABA, a major inhibitory neurotransmitter in the brain, it may depress all levels of the CNS, including the limbic and reticular formation. |
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| Adult Dose | 1-2 mg IV/IM |
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| Pediatric Dose | 0.01 mg/kg IV/IM |
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| Contraindications | Documented hypersensitivity; preexisting hypotension; narrow-angle glaucoma |
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| Interactions | Toxicity of benzodiazepines in CNS increases when used concurrently with alcohol, phenothiazines, barbiturates, and MAOIs |
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| Pregnancy | D - Unsafe in pregnancy
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| Precautions | Caution in renal or hepatic impairment, myasthenia gravis, organic brain syndrome, or Parkinson disease |
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| Drug Name | Diazepam (Valium) |
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| Description | Depresses all levels of CNS (eg, limbic and reticular formation), possibly by increasing activity of GABA. Third-line agent for agitation or seizures because of shorter duration of anticonvulsive effects and accumulation of active metabolites that may prolong sedation. |
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| Adult Dose | 5-10 mg IV q10-15min until symptoms resolve; not to exceed 30 mg |
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| Pediatric Dose | <30 d: Not established
30 days to 5 years: 0.2-0.5 mg IV (slowly) q2-5min until symptoms resolve; not to exceed 5 mg
>5 years: 1 mg IV (slowly) q2-5min until symptoms resolve; not to exceed 10 mg |
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| Contraindications | Documented hypersensitivity, hypotension, acute narrow-angle glaucoma |
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| Interactions | Increases toxicity of benzodiazepines in CNS with coadministration of phenothiazines, H1 blockers, barbiturates, alcohols, and MAOIs |
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| Pregnancy | D - Unsafe in pregnancy
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| Precautions | Caution with other CNS depressants, low albumin levels, or renal and hepatic disease (may increase toxicity); monitor for respiratory depression with high or repeated doses |
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| Drug Name | Midazolam (Versed) |
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| Description | Used as alternative in termination of refractory status epilepticus. Because water soluble, takes approximately 3 times longer than diazepam to peak EEG effects. Thus, clinician must wait 2-3 min to fully evaluate sedative effects before initiating procedure or repeating dose. Has twice the affinity for benzodiazepine receptors than diazepam. May be administered IM if unable to obtain vascular access. |
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| Adult Dose | 0.01-0.05 mg/kg (usually 0.5-4 mg, up to 10 mg) IV slowly over several min; may repeat q10-15min until adequate response achieved |
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| Pediatric Dose | <32 weeks: 0.5 mcg/kg/min IV infusion
>32 weeks: 1 mcg/kg/min IV infusion
Children: 0.05-0.2 mg/kg IV over 2-3 min, followed by 1-2 mcg/kg/min continuous infusion
Status epilepticus (refractory to standard therapy), > 2 months and children: 0.15 mg/kg followed by continuous infusion of 1 mcg/kg/min, titrating dose upward q5min until seizures controlled |
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| Contraindications | Documented hypersensitivity; preexisting hypotension, narrow-angle glaucoma, and sensitivity to propylene glycol (diluent) |
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| Interactions | Sedative effects may be antagonized by theophyllines; narcotics, cimetidine, ethanol, and erythromycin may accentuate sedative effects because of decreased clearance; reduce dose of thiopental by 15% when using together |
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| Pregnancy | D - Unsafe in pregnancy
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| Precautions | Caution in congestive heart failure, pulmonary disease, renal impairment, hepatic failure, neuromuscular disease, hypotension, and patients >60 y; monitor for respiratory depression with high or repeated doses; consider lower dosages in patients with organic brain syndrome and patients who may have inhibition of benzodiazepine metabolism and clearance (eg, using nicotine, taking cimetidine) |
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Drug Category: Antivenom
Used to neutralize the toxin of a widow spider bite.
| Drug Name | Antivenin Latrodectus mactans |
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| Description | Derived from horse serum and produced by Merck & Co., Inc. Consider for patients with grade 2 or grade 3 envenomations who are refractory to opiates and sedative-hypnotics and do not have risk factors for immediate hypersensitivity reactions. Some authorities advocate antivenom administration for certain patient groups, such as children and elderly persons. Package insert recommends skin testing for possible allergic reaction to the antivenom.
To mix the antivenom, dissolve 1 vial in 2.5 mL of sterile diluent with gentle agitation, then dilute this into a total volume of at least 20-50 mL NS. The package insert recommends intravenous injection over 15 min. However, adverse reactions may be averted by further diluting the antivenom (eg, to a total volume of 200 mL) and administering the infusion slowly (eg, over 1 h). Symptoms have been shown to improve within 1 h of antivenom administration and for as long as 48 h after envenomation. In Australia, antivenom for Latrodectus envenomation is available from Commonwealth Serum Laboratories and, in South Africa, from the South African Institute of Medical Research. Indications for antivenom use and routes of administration vary around the world. |
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| Adult Dose | 1 vial in 50-250 mL NS; administer IV infusion at 1 mL/min over 15 min, watching for signs of allergic reaction, then complete the infusion over 1 h |
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| Pediatric Dose | Administer as in adults |
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| Contraindications | Documented hypersensitivity; previous exposure to horse serum |
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| Interactions | None reported |
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| Pregnancy | C - Safety for use during pregnancy has not been established.
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| Precautions | Mortality from widow spider envenomation is extremely rare, and some argue against administration of antivenom when treatment may be more dangerous than the injury; some recommend routine premedication with antihistamines (H1 and H2 blockers); black widow spider envenomation is associated with abruptio placentae and fetal demise; benefits of antivenom administration in pregnancy must be weighed against risks |
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Drug Category: Immunizations
Tetanus immunization should be instituted following a black widow spider bite. Tetanus results from elaboration of an exotoxin from Clostridium tetani. A booster injection in previously immunized individuals is recommended to prevent this potentially lethal syndrome. Patients who may not have been immunized against C tetani products (eg, immigrants, elderly persons) should receive tetanus immune globulin (Hyper-Tet).
| Drug Name | Diphtheria-tetanus toxoid (dT) |
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| Description | Used for the passive immunization of any person with a wound that might be contaminated with tetanus spores. |
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| Adult Dose | Prophylaxis: 250-500 U IM in opposite extremity to tetanus toxoid lesion
Clinical tetanus: 3000-10,000 U IM |
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| Pediatric Dose | Prophylaxis: 250 U IM in opposite extremity as tetanus toxoid
Clinical tetanus: Administer as in adults |
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| Contraindications | Documented hypersensitivity; a history of any type of neurological symptoms or signs following administration of this product; FDA recommends that elective tetanus immunization be deferred during any outbreak of poliomyelitis because tetanus toxoid injections are an important cause of provocative poliomyelitis |
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| Interactions | Patients receiving immunosuppressants, including corticosteroids or radiation therapy, may remain susceptible despite immunization because of poor immune response; cimetidine may enhance or augment delayed-hypersensitivity responses to skin-test antigens; avoid concurrent use of medication with systemic chloramphenicol because it may impair amnestic response to tetanus toxoid; concurrent use of tetanus immune globulin may delay development of active immunity by several days (nevertheless, interaction is clinically insignificant and does not preclude its concurrent use) |
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| Pregnancy | C - Safety for use during pregnancy has not been established.
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| Precautions | Do not use to treat actual tetanus infections, or for immediate prophylaxis of unimmunized individuals (use tetanus antitoxin instead, preferably human tetanus immune globulin) diminished antibody response to active immunization may be observed in patients receiving immunosuppressive therapy; better to defer primary diphtheria immunization until immunosuppressive therapy discontinued; routine immunization of symptomatic and asymptomatic HIV-infected persons is recommended; persons with isolated immunoglobulin A (IgA) deficiency have potential for developing antibodies to IgA and could have anaphylactic reactions to subsequent administration of blood products that contain IgA; do not perform skin testing since the intradermal injection of concentrated gamma globulin may cause a localized area of inflammation that can be misinterpreted as a positive allergic reaction when it actually is a localized chemical tissue irritation; true allergic responses to human gamma globulin given in the prescribed IM mannerare
extremely rare; do not admix with other medications because usually incompatible |
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Drug Category: Antihistamines
Prevent the histamine response in sensory nerve endings and blood vessels. More effective in preventing histamine response than in reversing it.
Antihistamines act by competitive inhibition of histamine at the H1 receptor, which mediates the wheal and flare reactions, bronchial constriction, mucous secretion, smooth muscle contraction, edema, hypotension, CNS depression, and cardiac arrhythmias.
In the treatment of black widow spider envenomations, antihistamines are used before antivenom administration to reduce acute adverse reactions to the antivenom.
| Drug Name | Diphenhydramine (Benadryl) |
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| Description | Used for the symptomatic relief of allergic symptoms caused by histamine released in response to allergens. |
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| Adult Dose | 10-50 mg IV/IM q6-8h prn; not to exceed 400 mg/d |
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| Pediatric Dose | 5 mg/kg/d IV/IM or 150 mg/m2/d IV/IM divided qid; not to exceed 300 mg/d |
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| Contraindications | Documented hypersensitivity |
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| Interactions | Potentiates effect of CNS depressants; because of alcohol content, do not give syrup dosage form to patient taking medications that can cause disulfiramlike reactions |
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| Pregnancy | C - Safety for use during pregnancy has not been established.
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| Precautions | May exacerbate angle-closure glaucoma, hyperthyroidism, peptic ulcer, and urinary tract obstruction |
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Further Inpatient Care
- Admission to the hospital is indicated to the following patients:
- Severely symptomatic children
- Pregnant women
- Patients with a history of hypertension or heart disease
- Patients with intractable pain and contraindications to antivenom
- Patients with unusual complications of envenomation
- Patients who develop anaphylaxis to antivenom
- Discharge patients who experience relief with opioid analgesics, sedative-hypnotics, and/or antivenom (after a period of observation). Antivenom administration may reduce the need for hospitalization.
Further Outpatient Care
- Instruct patients to return if any of the following symptoms occur:
- Hematuria
- Rash
- Joint pain
- Swollen lymph nodes
- Difficulty breathing
- Signs of infection
In/Out Patient Meds
- Antihistamines and steroids should be given if serum sickness to antivenom develops. This is rare because treatment of widow spider envenomation usually requires only 1-2 vials of antivenom, and serum sickness usually occurs when more antivenom is given.
Deterrence/Prevention
- Pesticides may prevent exposures to widow spiders at home.
Complications
- Respiratory difficulty, reactive airway exacerbation
- Spontaneous abortion or preterm labor
- Hypertensive emergency with or without associated seizures (isolated normotensive seizures have not been described), acute myocardial infarction
- Rhabdomyolysis
- Priapism (rare)
- Compartment syndrome (rare)
- Toxic myocarditis (rare)
- Antivenom-associated complications
- Anaphylaxis, a type I (immediate) hypersensitivity reaction that may be life threatening, is characterized by urticaria, wheezing, and shock. It may occur to some degree in as many as 25% of patients given antivenom. Risk factors may include previous exposure to horse serum or antivenom or a history of reactive airways. It is treated with epinephrine, antihistamines, steroids, and ventilatory/circulatory support. One death has been reported from anaphylaxis to widow spider antivenom in the United States. The patient had a history of asthma and, after antivenom was administered, developed severe bronchospasm unresponsive to medical therapy.
- Serum sickness, a type III (delayed) hypersensitivity reaction characterized by fever, urticaria, lymphadenopathy, and arthritis, may occur 5 days to 3 weeks after antivenom administration. It usually is benign, self-limited, and treated with antihistamines and steroids. Serum sickness is dose related and uncommon following administration of widow spider antivenom because of the small amounts generally needed (1 or 2 vials).
Prognosis
- The vast majority of patients with widow spider envenomations recover fully.
Patient Education
Medical/Legal Pitfalls
- Sending a patient home who subsequently returns with persistent symptoms requiring antivenom and/or admission is a pitfall.
- Obtain informed consent before antivenom administration, if possible.
Special Concerns
- Envenomation is an uncommon occurrence with an extremely variable presentation.
- Treatment of envenomation often is based on speculation and anecdote, and much of the literature is contradictory.
- This article attempts to keep recommendations in agreement with the most current standards of care.
| Media file 1:
Black widow spider (Latrodectus mactans) with egg sac. Photo by Sean Bush, MD. |
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| Media file 2:
Black widow spider (Latrodectus mactans) and offspring. Photo by Sean Bush, MD. |
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- Watson WA, Litovitz TL, Klein-Schwartz W, et al. 2003 annual report of the American Association of Poison Control Centers Toxic Exposure Surveillance System. Am J Emerg Med. Sep 2004;22(5):335-404. [Medline].
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Spider Envenomation, Widow excerpt Article Last Updated: Aug 22, 2006
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