Pediatric emergency medicine trisk 2024 2024
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cm proximal to this level every 30 minutes for 6 hours, then at least every 4 hours
for a total of 24 hours. Table 90.24 is derived from a grading system suggested by
the Scientific Review Subcommittee of the American Association of Poison
Control Centers.
Any prehospital care (e.g., extremity immobilization) should be rechecked. If
an occluding tourniquet is inappropriately present, the physician should place a
more proximal constriction band and then cautiously remove the tourniquet,
being prepared to respond therapeutically to a systemic release of venom.
The older antivenin Crotalidae polyvalent (AVCP; Wyeth-Ayerst
Pharmaceuticals) is no longer available; it was derived from horse serum and was
highly antigenic. It has been replaced by CroFab, which was licensed in 2000 and
is a polyclonal, polyvalent Fab affinity purified antivenin (FabAV; CroFab
Protherics Medicines Development Ltd.) derived from sheep. It has significantly
fewer adverse reactions than seen with AVCP. CroFab is effective for rattlesnake
and cottonmouth/water moccasin envenomations. As copperhead venom was not
used in the development of CroFab, its efficacy in copperhead envenomizations is
unclear, especially in patients only with minor local symptoms and without
systemic effects. In 2018 mercury was removed from the CroFab manufacturing
process due to concerns of potential toxicity. For maximal venom binding, the
antivenin should be given within 4 to 6 hours of the snake bite. The benefits of
antivenin administration after 12 hours are questionable, and antivenin use
generally is not indicated after 24 hours (an exception may be continued
coagulopathy). The dosage regimen for CroFab is different than AVCP. As
unbound CroFab may be cleared before venom emerges from tissue deposits,
CroFab is given either on a fixed schedule or on a sliding scale. Relative
contraindications for use include known hypersensitivity to papain, papaya, or
CroFab. It is unknown whether CroFab can harm the fetus when administered to a
pregnant woman. Its use during pregnancy should be discussed with the regional
Poison Control Center.
For patients receiving CroFab, an initial dose of four to six vials is given over 1
hour. Pediatric patients should receive the same CroFab dose as adults as the
antivenom is dosed according to the amount of venom injected rather than body
weight. Skin testing is not needed for CroFab. Each vial is reconstituted with 18
mL of normal saline, and then all vials are mixed with normal saline to create a
final volume of 250 mL. The infusion should be started slowly, at a rate of 25 to
50 mL/hr for 10 minutes, while observing for allergic reaction. The rate should be
increased so the 250 mL is given over 1 hour. If mild allergic manifestations
develop, the infusion should be stopped and diphenhydramine (1 to 2 mg/kg IV)
