To Treat or Not to Treat, That is the Question
A number of factors should be considered in deciding the best approach to case management.
These factors include: Substance ingested, amount of substance ingested, co-ingestants, time post ingestion, prior intervention(s),
species/age of animal, and concurrent health problems (particularly problems that might interfere with detoxification or elimination
of the ingested substance, e.g., liver or kidney dysfunction)
In asymptomatic, recently exposed animals, it is important to attempt to determine the severity of exposure to the toxicant
(exposure assessment). Such an assessment will assist you in choosing the appropriate sequence of management steps to follow
(see Figure1). For example, if a dog has recently ingested an amount of an anticoagulant rodenticide that is well below a
reported toxic dose (less than or equal to 1/10th of an LD50*), then close monitoring at home for several days may be sufficient. Ingestion of higher doses may warrant administration
of an adsorbent such as activated charcoal (AC), with or without a cathartic, followed by close monitoring in the hospital.
In symptomatic animals, the first priority is to stabilize the patient and then to consider whether decontamination procedures
are warranted. In such situations, an exposure assessment may need to be postponed until a later time.
Figure 1. Treatment alogrithm for initial management of small animal intoxications. AC = activated charcoal, WBI = whole bowel
*The 1/10th of an LD50 rule of thumb is only a General Guideline. Non-toxic doses are dependent on a number of factors including the nature of the dose-response curve for the exposed species.
Extrapolations from available data are often required.
In many situations, even where there is a strong suspicion of intoxication, no specific toxicant can be identified and therefore,
no exposure determined. Fortunately, with many toxicant exposures, appropriate symptomatic and supportive care will result
in a positive case outcome. Sometimes a known toxicant may have been ingested, but there is no information available concerning
its toxicity to the particular animal species exposed. In such situations, extrapolation of toxicity data from other species
such as laboratory rodents may be all that is possible. Ultimately, the advice to "treat the patient and not the toxicant"
Prioritizing Your Priorities
Once a determination is made that an animal has been exposed to (or potentially exposed to) a toxicant or is intoxicated,
a general approach to case management should adhere to the following principles: (1) stabilize vital signs (this may include
administration of an antidote if sufficient information concerning a specific toxicant exposure is immediately available),
(2) obtain a history and clinically evaluate the patient, (3) prevent continued systemic absorption of the toxicant, (4) administer
an antidote if indicated and available, (5) enhance elimination of absorbed toxicant, (6) provide symptomatic and supportive
care, and (7) closely monitor the patient. Obviously, each situation is unique and one or more of the steps may be eliminated
or their priority changed depending on the circumstances of the case. For example, there may not be an antidote for a given
toxicant or a way to significantly enhance its elimination once it has been systemically absorbed. In some situations with
a known exposure, it may be critical to administer an antidote quickly. For example, in suspected cholinesterase-inhibiting
insecticide intoxications, administration of atropine may be critical to control life-threatening signs before proceeding
with subsequent management steps.