88
localized pain somewhat. If significant pain is present, immobilize the involved
extremity. Pressure immobilization with elastic bandage is not recommended as retention
of venom at the bite site increases local symptoms (Couser and Wiles, 1997) Oral
analgesics are useful for muscle pain.
If available, narcotics may be necessary for pain control, but care must be taken to
avoid hypotension and respiratory depression. A number of therapies for Latrodectus
envenomation (such as muscle relaxants and IV calcium gluconate) have been tried with
limited success.(Category 2 recommendation) Diazepam should be administered with
caution to an intoxicated victim as this potentiates CNS depression. There is little doubt
that antivenin is the most effective therapy, however the safety of the IV antivenin used
in North America is of concern. In Australasia and Japan, a different antivenin is used
IM with an excellent safety and efficacy record. Due to the difficulties of storing
antivenin its field use cannot be recommended. Immediate evacuation is recommended
for signs of serious envenomation.
(2) Fiddlebacks are often called brown recluses, but these spiders are not always
distinctively brown. They most often have a distinctive violin or fiddle-shaped mark on
the dorsal cephalothorax. They average 12 mm long with a leg span of up to 5 cm. The
bite of both sexes is equally venomous, although usually painless. Within a few hours, a
macule or vesicle may appear at the site. In a severe bite, erythema and blistering follow
within 6 to 12 hours. The classic picture is a hemorrhagic vesicle surrounded by a white
or pale ischemic zone, and then by an erythematous region--the so-called bull's-eye
lesion. By inspection of the lesion alone, however, it is usually impossible to differentiate
a Loxosceles bite from many other skin lesions and bites. Pruritus and rash can also
occur. Nausea, vomiting, headache, and fever are common systemic symptoms. The
lesion either resolves or becomes necrotic and indurated. This may require excision or
grafting. Symptoms of envenomation with fiddleback bites are caused by cell and tissue
injury and direct lytic action of sphingomyelinase on red cell membranes. Rarely, and
mostly in children, massive intravascular hemolysis develops early, often before the local
necrotic lesion is well established. If the systemic symptoms include pallor and bloody
urine, urgent evacuation is indicated. (Pitts RM in TCHA Poison Information Bulletin,
Oct 1992).
Treatment consists of local wound care. If the wound becomes necrotic and
extends to more than 1 cm in diameter, the use of oral dapsone may be indicated.
(Category 2 recommendation) Do not use dapsone unless the person has been tested for
G6P deficiency. The short-term application of ice packs to the bite site is as effective as
any other form of therapy. The patient may be placed on a corticosteroid, such as
prednisone 1 mg/kg daily for five days, during the acute phase.
REFERENCES:
Spider Bites
1) Vest DK in Boyer LV, McNally JT, and Binford, GJ: Spider Bites. In Auerbach P
(Ed) Wilderness Medicine, 4
th
ed, Mosby, St. Louis, MO, 2001, pp 829.
2) Couser GA and Wilkes GJ: A red-back spider bite in a lymphoedematous arm. Med
J Aust 1997; 166: 587- 588.
3) USP, Pharmacopeia of USA.
