Pediatric emergency medicine trisk 2017 2017
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Snakebite envenomation is a complex poisoning because of the combination of
the effects of venoms and the human and snake variables that influence venom
toxicity. Venoms are mixtures of potent enzymes, primarily proteinases, and low–
molecular-weight peptides that possess extensive pathophysiologic properties. A
crotalid venom often has a combination of necrotizing, hemotoxic, neurotoxic,
nephrotoxic, and cardiotoxic substances. Many venoms induce increased
endothelial permeability and venous pooling, creating intravascular depletion. A
transient hemoconcentration may be present during this plasma “leak.”
Hemotoxic effects induce hemolysis, fibrinogen proteolysis, and
thrombocytopenia, which along with activation of plasminogen, can lead to a
bleeding diathesis in severe envenomation. Respiratory failure may occur because
of pulmonary edema or a shock state.
Human factors that influence toxicity to snakebites include the victim’s size
and general health and wound characteristics. A small child is more susceptible to
a given volume of venom than a larger person and unfortunately, young children
are commonly bitten more than once. Fang penetration of a vessel or subfascial
compartment ensures a more rapid absorption and serious systemic effects.
Likewise, a bite on the head, neck, or trunk hastens systemic absorption.
