Derm Emergencies Flashcards
Within the United States, three genera
contain species whose bites are toxic to man:
● Latrodectus “Black Widows”
● Loxosceles “Brown Recluse”
● Eratigena Agrestis “Hobo Spider”
Latrodectus “Black Widows”
● Black body with red, hourglass shaped
markings on their abdomen
● Found in most states
● Non aggressive spiders; human bites
are often from accidental provocation.
● Webs can be found in corners of doors
or windows, underneath woodpiles, in
garages and sheds, undersides of
leaves, basements, etc.
Bites of the black widow spider:
● Painful bites
● Within 20- 60 minutes: localized
erythema develops, piloerection, and
sweating at the wound site.
● Numbness or aching pain may develop.
● A small red macule may develop to a
larger target lesion with a blanched
center and surrounding erythema
Black widows venom
● Venom contains a neurotoxin which releases
neurotransmitters: acetylcholine and
norepinephrine
● Bites may produce crampy abdominal pain
and muscle spasm (may mimic an acute
abdomen)
○ May be misdiagnosed as drug
withdrawal, appendicitis,
meningitis, tetanus, etc
● Hypertension
● Tachycardia
● Headache
● Nausea/vomiting
● Diaphoresis
Treatment for black widow spider bites
● Most require local wound care
● Patients at increased risk for serious complications? Very young,
very old, and cardiovascular disease
Mild Envenomation:
● Clean bite site
● Administer PO pain meds or benzodiazepines, as needed
● PO muscle relaxants may be helpful (evidence is lacking though, per UTD)
● Administer tetanus prophylaxis
Moderate to Severe Envenomation care for black widow spider bites:
● Local wound care and tetanus prophylaxis
● IV/IM opioids for pain
● IV/IM benzodiazepines to reduce the
frequency and severity of muscle spasms
● Administer antiemetic therapy for nausea
and vomiting
● Latrodectus antivenom, if severe
Don’t give IV calcium (an older treatment modality).
It does not appear to be effective
Antivenoms
can reduce pain, have more prolonged effect than analgesics,
can reduce the need for hospitalization
Loxosceles “Brown Recluse”
● Dark brown marking on their thorax in
the shape of a fiddle
● Most abundant in Midwest and
Southeast
● Recluses are named because they
will live in closets, attics, and
storage areas
● Bites occur when the spider feels
threatened or provoked
Loxosceles “Brown Recluse” bite symptoms
● Initial bite is usually painless
● Pain increases over the next 2-8 hours,
may become severe
● Site may be identified by two small
cutaneous puncture marks with
surrounding redness
● Usually a red plaque or papules is
present, developing a central pallor
● Self-limiting and may resolve in one
week
● In some patients, the lesion will
develop a dark, depressed center
over 1-2 days that results in a dry
scab that ulcerates.
The hallmark “red, white, and blue” is a
central violaceous area surrounded by
blanched skin, surrounded by large area of
erythema - seen with which bite?
Loxosceles “Brown Recluse”
Brown recluse venom
● Venom contains many enzymes and biologically active substances that
contribute to destruction.
● Systemic symptoms are an infrequent complication and may
develop within 1–2 days:
○ Malaise, nausea, vomiting, headache, fever, myalgias.
● Rare but severe symptoms: angioedema, renal failure, hemolytic
anemia, rhabdomyolysis, hypotension, DIC, coma, death
Treatment for Loxosceles “Brown Recluse” bite
● Clean the bite
● Apply cold compress
● Analgesics
● Administer tetanus prophylaxis
● Antibiotics can be used to treat
secondary infection
For dermal necrosis from brown recluse bite:
● There is an antivenom used in Brazil, but it’s not available in the US
● Necrotic wounds may require surgical excision/debriding later on, but
not initially
● Don’t use dapsone (an older treatment); no clear evidence of benefit
Eratigena Agrestis “Hobo spiders”
● Brown in color with a gray herringbone
pattern on the abdomen
● Build funnel shaped webs in
basements, wood piles, and bushes
● Most bites occur July - September
● Aggressive house spider
● Most common cause of necrotic
spider bites
● Live in most climates Alaska-Utah
Eratigena Agrestis “Hobo spiders” bites
● Bite sites may have localized
erythema, itching, pain, and
swelling
● Little documentation supports
the occurrence of necrosis
Scorpiones “Scorpions” sting
● Sting produces an immediate, sharp
burning pain; followed by numbness
● Regional lymph node swelling
Scorpion sting venom
● Venom contains a powerful neurotoxin
that produces muscle spasm, blurred
vision, slurred speech, excessive salivation,
respiratory distress, myocarditis
● Infant and young children are at the
greatest risk
Scorpion sting treatment
● Mild stings only need symptomatic
treatments (analgesics and ice)
● Any child stung should be hospitalized to monitor respiratory, cardiac, and neurologic status
● Antivenom is the treatment of choice for pts with severe systemic symptoms
Most common cause of drug
reaction is _____
antibiotics
Exanthematous Eruptions
● An adverse hypersensitivity reaction to
ingested or parenterally administered
drugs
● Most common form of drug eruptions,
95% of skin reactions
● Macules and/or papules bright red;
Lesions become confluent
● Typically starts on the trunk and spreads
in a symmetric fashion
● Pruritus is almost always present
● May mimic viral exanthem, like measles
Exanthematous Eruptions course
● Can occur within 1 week of starting
therapy to 1-2 days after stopping
treatment
● Typically resolves in 7-14 days
● After discontinuing the drug, the rash
usually fades, however it may worsen
for a few days
● Eruption usually recurs with
rechallenge (not always)
Exanthematous Eruptions treatment
● Identify the offending drug and discontinue it
● PO antihistamine for itching (ie. benadryl)
● Glucocorticoids
○ Potent Topical Preparation- May help speed resolution of
eruption (ie. hydrocortisone, betamethasone)
○ Oral or IV- Provides symptomatic relief (ie. solumedrol)
Exanthematous Eruptions treatment
● Patients must be aware of their specific
drug hypersensitivity and that other drugs
of the same class can cross-react
● Consider wearing a medical alert bracelet
Urticaria and Angioedema
● Two variations of the same process,
IgE mediated
● Urticaria: characterized by
pruritic red wheals of various
sizes
● Individual lesions that last less
than 24 hours, but new lesions
may occur
Angioedema: a larger edematous
area that involves the dermis and
subcutaneous tissues and is ill
defined
● Angioedema is nonpruritic, and
lasts for 1-2 hours
Urticaria and angioedema indicate an _____
immunoglobulin igE mediated hypersensitivity
Signs and symptoms of Urticaria and Angioedema include:
○ Pruritus, urticaria, cutaneous flushing, angioedema, nausea, vomiting, diarrhea, abdominal pain, nasal congestion, rhinorrhea, laryngeal edema, and bronchospasm or hypotension
