Page 474 - Clinical Small Animal Internal Medicine

442 Section 5 Critical Care Medicine

only asymptomatic patients should be made to vomit, as clearance by the liver. If prolonged vomiting occurs after
VetBooks.ir the risk for aspiration pneumonia is greatly increased by apomorphine treatment, administration of an injectable
antiemetic (e.g. maropitant, metoclopramide, or ondan-
CNS dysfunction or neuromuscular weakness. The risk
of esophageal or oropharyngeal injury is increased if
occur after apomorphine administration. The sedative
large or sharp objects have been ingested along with the setron) is indicated. Rarely, significant sedation will
toxin. Though uncommon, these possible complications effects of apomorphine can be reversed using naloxone.
must be considered and discussed with the client when Induction of emesis in cats is more challenging than in
deciding whether or not to induce emesis in a patient dogs. Injectable administration of an alpha‐2‐adrenergic
that has ingested a toxin. Patients that have ingested agonist is currently the method of choice. Xylazine
caustic substances (e.g., bleach) or hydrocarbons (e.g., is commonly given at a dose of 0.44 mg/kg IM for
gasoline) should never be made to vomit. Ingestion of this purpose; as much as 1.1 mg/kg can be given.
zinc phosphide rodenticide leads to liberation of phosphine Dexmedetomidine (20–40 μg/kg IM) can also be used.
gas in the acidic environment of the stomach; induction One major drawback to the use of alpha‐2‐adrenergic
of emesis following zinc phosphide rodenticide must be agonists for this purpose is that profound sedation
done carefully in a well‐ventilated area (ideally, outdoors) may occur. Reversal of the alpha‐2‐adrenergic agonist
to reduce the risk of dangerous phosphine gas inhalation using yohimbine (0.1 mg/kg IM or IV) or atipamezole
by veterinary staff. (50 μg/kg IM) is recommended following emesis to pre-
Hydrogen peroxide and apomorphine are the two vent sedation from interfering with interpretation of
most common agents used to induce emesis in dogs. symptoms of poisoning.
Due to an increased risk of side‐effects, the use of syrup
of ipecac, sodium chloride salt, dishwashing liquid or Gastric Lavage
mustard powder is not recommended. Inducing emesis When induction of emesis is unsuccessful or contraindi-
is typically easy in canine patients. Hydrogen peroxide cated and an ingested toxicant is likely to cause signifi-
(3%) can be given PO at a dose of 2.2 mL/kg (up to cant morbidity or mortality, gastric lavage may be
a maximum of 45 mL) and repeated if vomiting has considered. Gastric lavage should always be done under
not occurred within 10–15 minutes of administration. general anesthesia (unless the patient is already uncon-
Hydrogen peroxide causes vomiting by acting as a scious), and a cuffed endotracheal tube should always be
local irritant in the oropharynx and stomach. Rarely, placed to guard the airway against aspiration of gastric
protracted vomiting can occur after administration. contents. Lavage is performed using warm (body temper-
Occasionally, mild side‐effects such as lethargy and diar- ature) water given through a large orogastric tube, keeping
rhea can occur. Very rare instances of symptomatic gastric the head below the level of the chest throughout the pro-
ulceration or even gastric dilation and volvulus (GDV) cedure to discourage aspiration of gastric contents (which
have been anecdotally reported following administration can occur even in the presence of a cuffed endotracheal
of hydrogen peroxide. A prospective observational study tube). Initial lavage volumes are typically 5–10 ml/kg, and
reported a relatively low incidence of mild side‐effects lavage is repeated until the fluid obtained from the stom-
(14%) in 70 clinical canine patients following induction ach is completely clear. If indicated, a dose of activated
of emesis using hydrogen peroxide; no serious or life‐ charcoal can then be given through the orogastric tube
threatening side‐effects were reported in this study. prior to its removal. The tube should be kinked in more
Apomorphine is a centrally acting emetic agent that than one place during removal from the stomach to pre-
reliably induces emesis in dogs by stimulation of the vent fluid within the tube from spilling into the airway.
chemoreceptor trigger zone. It can be given as a 0.03– Gastric lavage carries risks, including anesthesia and
0.04 mg/kg intramuscular (IM) or IV injection. Vomiting aspiration pneumonia; careful consideration of the
typically occurs soon after apomorphine injection. risk:benefit ratio must precede this intervention.
If vomiting does not occur, dosing can be repeated once
or twice more, but the drug may depress the vomiting GI Adsorption
center in the medulla, so repeat administration may be Activated charcoal (AC) has been, and will likely con-
unlikely to induce vomiting if the first dose was unsuc- tinue to be, one of the most common treatments admin-
cessful. Conjunctival application of apomorphine is also istered to veterinary patients who have ingested a toxin.
a very effective way of inducing emesis in dogs. The con- The use of AC in human medicine has recently been
junctiva should be thoroughly flushed after emesis to critically reevaluated, and routine use has been discour-
limit further absorption of apomorphine and decrease aged due to a lack of evidence that its administration
the risk of CNS depression or protracted vomiting. PO affects outcome. There have been no published veteri-
administration of apomorphine to induce emesis is not nary studies comparing conventional therapy with AC
recommended due to slow absorption and high first‐pass versus conventional therapy alone. Inherent differences