Page 475 - Clinical Small Animal Internal Medicine

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between veterinary small animal patients and human Few dogs (and almost no cats) willingly ingest AC
VetBooks.ir patients make the veterinary application of human solutions. One commonly utilized clinical method of
administration involves combining the charcoal with a
guidelines questionable. Veterinary patients may be
more likely than human patients to ingest large quanti-
binds to the charcoal and reduces binding capacity, a
ties of toxins, and paradoxically veterinary patients may small amount of highly palatable food. While the food
present for medical care sooner after ingestion than published veterinary study suggests the reduction in
human patients due to the intentional nature of many toxin‐binding capacity is clinically insignificant.
human intoxications. Furthermore, advanced treatments
such as hemofiltration for toxin removal or prolonged, Cathartics
aggressive hospital‐based care for treatment of organ Cathartics are given to speed GI transit times in an effort
dysfunction are more readily available and more often to decrease the time a toxin is available for absorption
pursued in human medicine than in veterinary patients, within the GI tract. The two types of cathartics used in
making it that much more important to limit toxin veterinary medicine are saccharides (e.g., sorbitol) and
adsorption in veterinary patients as much as possible saline (e.g., magnesium sulfate); sorbitol is the most
prior to signs of intoxication. commonly used cathartic, and it is most commonly
Products containing AC are administered at a dose of stocked in veterinary hospitals as an AC‐sorbitol com-
1–5 g/kg body weight PO or via orogastric intubation to bination product. Because cathartics such as sorbitol act
bind any remaining toxin within the GI tract and prevent by drawing water into the GI lumen, significant risk of
further absorption of the toxin. AC administration is dehydration and hypernatremia exists with repeated use
indicated when the ingested poison binds to AC, is likely of these products. When a cathartic is used, it is typically
to cause significant toxicity, and has been recently only administered as a one‐time dose. The most com-
ingested (within the past 4–6 hours) and/or undergoes mon clinical practice is to give only the first dose of AC
enterohepatic recirculation. Repeated dosing (every with sorbitol, utilizing AC products without a cathartic
4–6 hours for four total doses) is recommended for for repeated doses.
dangerous toxins for which enterohepatic recirculation
is known to occur and no antidote is available. The use Decontamination of Blood
of AC‐containing products may lead to vomiting, and
aspiration of gastric contents or charcoal creates a risk Extracorporeal Therapies
of pneumonia. Injection of an antiemetic prior to AC One of the most effective methods to treat certain
administration may help decrease the incidence of emesis. poisonings is removal using extracorporeal therapies
AC may bind water within the GI tract, and repeated such as hemodialysis and hemoperfusion. Hemodialysis
doses have been associated with dehydration and involves circulating blood through an extracorporeal cir-
hypernatremia in rare cases. When repeated doses of AC cuit and allowing for transfer of solutes and water across
are needed, many sources recommend the repeat doses a semipermeable membrane. Toxins are good candidates
be given at a lower dose (for instance, half the initial for removal via hemodialysis if they are relatively small
administered dose), and IV fluid administration is rec- (<1500 daltons), poorly protein bound and with a low
ommended to help prevent significant dehydration. It is volume of distribution. Ethylene glycol and aspirin are
also important that veterinarians and clients know which examples of compounds that are readily cleared by hemo-
patients have received AC so that the resultant black dialysis. Hemoperfusion refers to the direct exposure of
stools are not misinterpreted as melena. blood in an extracorporeal circuit to an adsorbent col-
Activated charcoal binds to most but not all toxins; it umn of charcoal or (less commonly) a different adsorbent
does not bind alcohols, heavy metals, or small organic specially designed to bind a specific toxin. Hemoperfusion
molecules. Use of AC is therefore not indicated for toxic greatly increases the number of poisons that can be
ingestions of xylitol, ethylene glycol, zinc, nitrates, or removed using extracorporeal therapy. Hemodialysis and
sodium chlorate, among others. It is important to con- hemoperfusion require specialized, often expensive,
firm that the suspected toxin binds to AC prior to equipment and highly trained personnel. The availability
administration of AC. If the binding affinity of a poison of hemoperfusion is currently limited in veterinary medi-
to AC is unknown by the clinician, a poison control cine, but the number of facilities offering this potentially
hotline should be contacted prior to administration. life‐saving intervention will likely increase in the future.
Studies have shown that the timing of AC administration
in relation to toxin ingestion directly influences the Intravenous Lipid Therapy
percentage of ingested toxin that is bound within the GI Administration of intravenous lipid emulsions (IVLE) is
tract. If AC use is indicated, it is important that the treat- a common therapy for the treatment of poisoning with
ment be administered as soon as possible. lipophilic toxins. IVLE therapy was first used to treat