Lecture 19: Basic Approach to Treatment of Poisoned Animals 2

what is the body’s natural way of removing things?

emesis

do not induce vomiting if the patient

• is a horse, ruminant, rodent, rabbit, reptile, bird

• is not fully alert and fully conscious

• has any significant respiratory compromise

• has abnormal pharyngeal reflexes

• is seizuring or has imminent risk of seizures

• has already vomited multiple times

• has ingested substance with rapid onset of action 

do not indice vomiting if

• re-exposure to the nesophagus, pharynx, or mouth will cause additional injury (caustic/corrosive agents, ingested toxin is mixed with something that can damage the esophagus)

• toxin is a volatile hydrocarbon or petroleum distillate 

use caution and avoid emesis if the patient has

• a seizure condition

• serious heart disease

• megaesophagus

• recent abdominal or chest surgery or trauma

how long after toxin ingestion does emesis become futile?

it depends on:

• consistency and amount of material in stomach

• caloric density of stomach contents

• fat content of stomach contents

• intragastric pressure

• the toxin ingested

liquids 

• generally pass quickly in an empty stomach

• gastric emptying starts within 15-45 minutes, complete within 1-4 hours 

solids

• are retained in stomach until almost liquid

• some non-absorbable solids can remain in stomach for weeks to months if no outflow obstruction or mucosal irritation

when do cats fed a meal with barium show gastric emptying?

within 30-60 minutes, complete within 9-12 hours

what can help determine if a stomach is full?

x-rays

rule of thumb for emesis

• the sooner, the better

• < 30 minutes post-ingestion is best

• up to 2 hours is reasonable

• > 4 hours can be questionable

what is the major risk of emesis?

aspiration

aspiration is rare in

dogs, cats, ferrets, pigs

when should emesis be done at home?

• if transport time to vet clinic is > 30 minutes

• if you are convinced that the patient has no “DO NOT” conditions, the owner can follow instructions and give the emetic

what is the best emetic for home use?

hydrogen peroxide 3%

hydrogen peroxide 3% MOA

irritates pharyngeal and gastric mucosa 

risks of hydrogen peroxide 3%

• rarely: aspiration and lung injury

• rarely: can cause mucosal erosions

how many times can you repeat hydrogen peroxide 3%?

1-2 times if no effect within 10-15 minutes

time to effect for hydrogen peroxide 3%

• within 10-20 minutes

• animal may vomit multiple times

efficacy for hydrogen peroxide 3% is very good in

dogs, ferrets, pigs

using hydrogen peroxide 3% is less effective in

cats

what is less effective or more dangerous than hydrogen peroxide?

• table salt

• liquid dishwashing detergent

• copper sulfate

• dry mustard powder

• manual pharyngeal stimulation

why should syrup of ipecac not be used?

horrible taste, cardiotoxic, CNS depressant, prolonged vomiting, diarrhea, etc

apomorphine

• synthetic derivative of morphine

• stimulates dopaminergic receptors in CRTZ in dogs

• IV administration preferred

• single use only as vomit center is depressed following initial CRTZ stimulation

• produces excitement in cats

xylazine

• activates alpha 2-receptors in CRTZ in dogs

• works well in cats in conjunction with pre-surgical sedation

apomorphine usually comes as a

6mg tablet

apomorphine is unstable in

light, air, and solution

what is the most common way to administer apomorphine?

place tablet or portion of tablet under eyelid in conjunctival sac

ropinirole

• dopamine D2 agonist

• developed for human Parkinson’s disease

• formulated as ophthalmic solution for dogs only

• 0-30 min for effect

• can give second dose after 20 minutes

• avoid human skin exposure

if decontamination is necessary but emesis is unsafe, then what do you consider?

gastric lavage

do not perform gastric lavage if

• the toxin ingested is caustic, corrosive

• volatile hydrocarbon

• an increased risk of gastric perforation exists

• if sharp objects are in the stomach

gastric lavage is indicated over emesis if

• the patient has altered mental status

• the patient has respiratory compromise

• emesis is unsuccessful

how should gastric lavage be performed in small animals?

under anesthesia, with a cuffed ET tube in place

anesthesia and endotracheal tube are not required for gastric lavage in

horses or ruminants 

what can help determine if risks from toxin outweigh risks from lavage?

toxic dose calculations

complications with gastric lavage

• aspiration (major risk)

• damage to GI tract

• fluid and electrolyte imbalances

what is the technique for placing a rumen lavage?

• animal is not anesthetized

• using a mouth gag, place large tube into rumen

• easiest if you have a source of running water

when should you consider a gastrotomy or rumenotomy?

• large items or imbedded items in the stomacg/rumen

• if emesis or lavage not safe or unlikely to be effective

when should you consider an endoscopic removal?

• if discrete item or imbedded item in stomach

• if emesis or lavage not safe or unlikely to be effective 

what is used for whole bowel irrigation?

polyethylene glycol → give large amount via stomach tube and the volume forces GI contents through intestines quickly

what is used for massive overdoses of sustained release drugs or toxins poorly bound by activated charcoal?

polyethylene glycol

oral chelators

• used more in large animals

• form insoluble compounds in GI tract to decrease absorption