Black widow spider bite
(Redirected from Black widow)
Background
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- Identification: red hourglass on otherwise black spider. Females tend to be larger and deliver more venom [1]
- Genus: Latrodectus
- Black widows live in southern Canada and every U.S. state except Alaska. Bites are more common in warmer months [2]
- Aptly named because of their sexual cannibalism (but only occurs approximately 2% of the time)[3]
- Most venomous spiders in North America[4]
- Venom several times more potent than rattlesnake venom
- Most people who are envenomated have no serious damage due to the low volume of venom delivered.[5]
- Rarely bites can be fatal
- High risk are the young, very old, and the infirm.[6]
Mechanism
- α-Latrotoxin envenomation causes massive release of neurotransmitters (norepinephrine, dopamine, acetylcholine, glutamate and GABA) from the nerve terminals → muscle cramps, tachycardia, hypertension
- This clinical envenomation syndrome is known as latrodectism
Clinical Features
Local
- Pinprick sensation; then increasing local pain that may spread to entire extremity
- Erythema appears 20-60 min after the bite; may develop characteristic halo or targetoid lesion
- Pain begins to abate after several hours and disappears by 2-3d
Systemic
- Muscle cramp-like spasms in large muscle groups (although exam rarely reveals rigidity)
- Pain becomes generalized
- Severe abdominal wall musculature pain and cramping
- Difficult to differentiate from peritonitis
- Headache, nausea/vomiting, diaphoresis, photophobia, dyspnea
- A-fib, myocarditis, priapism, and death are rare
Grading System
- Grade 1: Range from no symptoms to local pain at the envenomation site with normal vital signs
- Grade 2: Involve muscular pain at the envenomation site to migration to the trunk, diaphoresis at bite site and normal vital signs
- Grade 3: Include grade 2 with abnormal vital signs; diaphoresis distant to envenomation site, generalized myalgia to back, chest and abdomen, nausea vomiting and headaches.
Differential Diagnosis
Envenomations, bites and stings
- Hymenoptera stings (bees, wasps, ants)
- Mammalian bites
- Closed fist infection (Fight bite)
- Dog bite
- Marine toxins and envenomations
- Toxins (ciguatera, neurotoxic shellfish poisoning, paralytic shellfish poisoning, scombroid, tetrodotoxin
- Stingers (stingray injury)
- Venomous fish (catfish, zebrafish, scorpion fish, stonefish, cone shells, lionfish, sea urchins)
- Nematocysts (coral reef, fire coral, box jellyfish, sea wasp, portuguese man-of-war, sea anemones)
- Phylum porifera (sponges)
- Bites (alligator/crocodile, octopus, shark)
- Scorpion envenomation
- Reptile envenomation
- Spider bites
Evaluation
- Generally clinical diagnosis
- For high-risk patients (pregnancy, children, older adults w/ cardiovascular issues), rule out peritonitis, UTI, and rhabdomyolysis
- CBC
- Creatinine phosphokinase
- Lactic acid
- UA
Management
- Local wound care, analgesia and tetanus prophylaxis are mainstays of treatment
- Grade 1: Cold packs and NSAIDs
- Grade 2/3: IV Opioids and Benzodiazepines
- Antivenin - indicated for systemic illness only
- Dosage: Usual dose is one to two vials diluted in 50 to 100 mL 5% dextrose or 0.9% sodium chloride, then infused over 1 hour
- Use is controversial - Morbidity (pain, cramping and autonomic disturbances) are high, but mortality is low. Antivenin is horse serum derived, and can lead to anaphylaxis and serum sickness
- Consider for: Pediatric patients, pregnant women (category C), elderly
Not Indicated
- Routine antibiotic use is not indicated
- IV calcium gluconate to reduce muscle spasm is an outdated therapy not favored by toxicologists[7]
Disposition
- Generally may be discharged
- Consider admission for:
- Symptoms of moderate or severe envenomation
- Pregnant women
- Children
- Preexisting cardiovascular disease or hypertension
See Also
External Links
References
- ↑ Maretić Z. Latrodectism: variations in clinical manifestations provoked by Latrodectus species of spiders. Toxicon. 1983;21(4):457-466. doi:10.1016/0041-0101(83)90123-x
- ↑ Isbister GK, Fan HW. Spider bite. Lancet. 2011;378(9808):2039-2047. doi:10.1016/S0140-6736(10)62230-1
- ↑ Hack, J. (2021). Spider's Secret. ACEP NOW, 40(12), 16–18.
- ↑ Hack, J. (2021). Spider's Secret. ACEP NOW, 40(12), 16–18.
- ↑ Hack, J. (2021). Spider's Secret. ACEP NOW, 40(12), 16–18.
- ↑ Hack, J. (2021). Spider's Secret. ACEP NOW, 40(12), 16–18.
- ↑ Clark RF et al. Clinical presentation and treatment of black widow spider envenomation: a review of 163 cases. Ann Emerg Med. 1992 Jul;21(7):782-7.