3
- Calcium gluconate (10% soln) IV over 10-20 min
-
adults:
1.0
gm/dose
- children: 50 mg/kg/dose up to 250 mg/kg/day
- repeat every 3-4 hr prn
- if first dose produces < 1 hr of pain relief, repeat doses unlikely to be beneficial
- Methocarbamol (10% soln) IV over 5-10 minutes
- adults: 1.0 gm initially, followed by 0.5-1.0 gm in 250-500 ml D
5
W over 3-4 hr
-
children:
15
mg/kg
every
6
hr
- hypertension usually responds to bed rest, muscle relaxants, analgesics, and sedation; specific
antihypertensives can be used if necessary
- Antivenin: produced by Merck, Sharp and Dohme (Antivenin Latrodectus mactans); effective for
all Latrodectus species; blocks ability of venom to bind to synaptic membranes
- indications for its use are controversial - justifiable for significant envenomations in patients who
are < 16 yr, > 60 yr, pregnant, or have a history of cardiovascular disease or other major medical
problems; may be considered in the rare patient with severe envenomation who is otherwise
healthy;
administration
solely
to
reverse
significant pain unrelieved by other measures is
effective,
but
controversial
due
to the risks of complications (see below)
- informed consent should be obtained
- epinephrine at the bedside (tape to IV bag)
- skin test (outlined in package insert)
- after negative skin test, premedicate with IV antihistamines (H1 & H2 blockers)
- give 1 vial diluted in 50 to 100 ml of NS IV over 15 minutes (with the physician @ the bedside)
- generally, 1 vial is adequate; a second can be administered if necessary
- majority of symptoms resolve within a few hr of antivenin
- adverse reactions to antivenin: anaphylaxis (IgE mediated), anaphylactoid reaction (direct
complement activation), or serum sickness (IgG, IgM mediated; less common than with snake
antivenin
[less
foreign
protein
infused])
- clinical course usually benign, but significant pain and spasm can persist for 12 to 48 hr
c.
Disposition/Outcome:
- if symptomatic (particularly if very young, very old or underlying medical problems) admit for
observation
- reliable, adult patients in good health with normal vital signs and easily controlled symptoms can
be discharged home for bedrest
- current mortality rate from widow spider venom poisoning in the United States is < 1%
- recovery may be slow; weakness, fatigue, paresthesias, headache, and insomnia may persist for
several
months
B. Brown Spiders (Loxosceles sp.):
1.
Introduction:
- the "fiddle-back" or "violin" spider
- 13 species in the U.S.; the brown recluse (L. reclusa) being the best known
- violin-shaped marking on the dorsal aspect of the cephalothorax
- 3 pairs of eyes (most spiders have 4 pairs)
- adult body is 10 to 15 mm in length; leg span of 2-3 cm
- both the male and female are dangerous
- L. reclusa is found throughout the southern, south-central, and midwestern U.S.; other species occur
in
the
west
- these spiders are easily transported about the country; therefore, possible for envenomations to occur
in
any
locality
- all Loxosceles spiders capable of causing dermonecrosis ("necrotic arachnidism"), but most bites
result
in
insignificant
lesions
- many other etiologies can produce similar lesions: other spiders, ticks, scorpions, ants, fleas, kissing
