View source for Black widow spider bite

==Background==
[[File:Western Black Widow (Latrodectus hesperus).jpg|thumb|Black widow spider]]
[[File:Blackwidow macro.jpg|thumb|Classic "hourglass" marking shape on ventral side of ''L. hesperus''.]]
*Identification: red hourglass on otherwise black spider. Females tend to be larger and deliver more venom <ref>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 </ref> 
*Genus: ''Latrodectus''
*Black widows live in southern Canada and every U.S. state except Alaska. Bites are more common in warmer months <ref>Isbister GK, Fan HW. Spider bite. Lancet. 2011;378(9808):2039-2047. doi:10.1016/S0140-6736(10)62230-1</ref> 
*Aptly named because of their sexual cannibalism (but only occurs approximately 2% of the time)<ref>Hack, J. (2021). Spider's Secret. ACEP NOW, 40(12), 16–18. </ref> 
*Most venomous spiders in North America<ref>Hack, J. (2021). Spider's Secret. ACEP NOW, 40(12), 16–18. </ref> 
**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.<ref>Hack, J. (2021). Spider's Secret. ACEP NOW, 40(12), 16–18. </ref>
*Rarely bites can be fatal
**High risk are the young, very old, and the infirm.<ref>Hack, J. (2021). Spider's Secret. ACEP NOW, 40(12), 16–18. </ref>
  

===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 pain|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==
{{Bites and stings DDX}}

==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<ref>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.</ref>

==Disposition==
*Generally may be discharged
*Consider admission for: 
**Symptoms of moderate or severe envenomation 
**Pregnant women 
**Children 
**Preexisting cardiovascular disease or hypertension

==See Also==
*[[Spider bites]]

==External Links==


==References==
<references/>

[[Category:Environmental]]
[[Category:Dermatology]]