Lecture 5 2/4/25 Flashcards
What are the four components of the emetic reflex?
-visceral receptors
-vagal and sympathetic afferent neurons
-chemoreceptor trigger zone
-emetic/vomiting center
What are the two pathways that trigger the emetic center?
-humoral pathway
-neural pathway
What are the characteristics of the humoral pathway?
-involves bloodborne substances
-triggers emetic center indirectly via the chemoreceptor trigger zone
What are the characteristics of the neural pathway?
-involves inflammation, infection, malignancy, or toxicity of the GI tract
-triggers emetic center directly
What are the inputs to the emetic center?
-chemoreceptor trigger zone
-vestibular apparatus
-cerebral cortex
-abdominal viscera
What things act at the chemoreceptor trigger zone to trigger the emetic reflex?
-drugs, including chemo drugs, bacterial toxins, and opioids
-metabolic waste products, including uremic toxins, ammonia, and ketones
What things act at the vestibular apparatus to trigger the emetic reflex?
-motion sickness
-vestibular inflammation or trauma
How does the vestibular input path vary between dogs and cats?
-in cats, the vestibular input goes right to the emetic center
-in dogs, the vestibular input first goes to the chemoreceptor trigger zone
What things act at the cerebral cortex to trigger the emetic reflex?
-sight/smell/thoughts
-extreme fear
-anticipation of pain
What things act at the abdominal viscera to trigger the emetic reflex?
-gastric or intestinal distension
-inflammation/irritation of the viscera, peritoneum, or pharynx
What are the indications for antiemetic therapy?
-animal is NOT suffering from GI obstruction or toxicity
-vomiting is severe/persistent
What are the characteristics of maropitant/cerenia?
-prevents vomiting mediated via CRTZ and emetic center
-may be a better anti-emetic than anti-nausea drug
-well tolerated, but can see vomiting or hypersalivation
What are the characteristics of ondansetron?
-may better a better anti-nausea drug than maropitant
-better function when giving parenterally
-side effects include sedation, fecal incontinence, and p-glycoprotein substrate (caution in collies)
What are the characteristics of metoclopramide?
-not a great antiemetic or antinausea drug
-more often used for prokinetic effects
-side effects include restlessness, spasms, aggression, hyperactivity, and or sedation
-interacts with lots of drugs
What are the steps to approaching a vomiting patients?
-differentiate between vomiting, regurgitation, and dysphagia
-determine chronicity
-describe frequency
-describe severity
-generate differentials
-create diagnostic and therapeutic plans
What are the extra-GI differentials for vomiting?
-hepatic dz
-renal dz/azotemia
-pancreatitis
-endocrine dz
-CNS dz
-motion sickness
-pyometra
-drug-induced
What are the acute primary GI differentials for vomiting?
-obstructive
-nutritional
-neoplastic
-infectious
-iatrogenic
-toxic
What are the chronic primary GI differentials for vomiting?
-inflammatory
-infectious
-neoplastic
-anomalous
How does the work up/treatment approach differ between mild/acute/uncomplicated cases and severe/recurrent/chronic cases?
-mild/acute/uncomplicated cases can be approached symptomatically
-severe/recurrent/chronic cases warrant a diagnostic workup
Which diagnostics should be considered with mild/acute/uncomplicated cases of vomiting?
-PCV/TS
-zinc sulfate fecal float
-abdominal radiographs
What are the therapy options for mild/acute/uncomplicated vomiting?
*easily digestible, low residue diet
–small, frequent meals
–given for 3-5 days for until resolution and then transitioned back to regular diet
*antiemetic or antinausea medications
What is most important about monitoring a mild/acute/uncomplicated vomiting case?
if there is no improvement in 48 hours, additional diagnostics should be performed
What are the components of a diagnostic workup for severe/recurrent/chronic cases of vomiting, as well as unresolved acute cases?
-CBC
-chem + electrolytes
-UA
-zinc sulfate fecal float
-spec cPL/CPLI (dogs) or fPL/fPLI (cats)
-abdominal radiographs
-abdominal ultrasound
What are the indications for hospitalization of a patient with acute vomiting?
-fever
-dehydration
-abdominal pain
-hematemesis
-hemorrhagic diarrhea/melena
-continued vomiting despite outpatient supportive care
-known toxin exposure
-neonate or toy breed (hypoglycemia concerns)
What is the therapy for severe/recurrent/chronic vomiting?
-easily digestible, low residue food with similar instructions as mild cases
-potential for GI diet to become long term if cases are recurrent/chronic
What are the characteristics of bilious vomiting syndrome?
-vomiting of bile-stained material
-often seen in dogs that are fed once daily
-diagnosed via response to treatment
What is the treatment for bilious vomiting treatment?
-feed 2 to 3 smaller meals per day
-give late night snacks
-possibly add in an appetite suppressant
What are the characteristics of acute gastritis etiology?
-can be primary or secondary
-cause often not determined
-can occur with foreign materials, chemical irritants, toxins, systemic disease, parasites, and bacteria
What are the possible pathophysiologies of acute gastritis?
-ingestion of substances that disrupt gastric-mucosal barrier
-decreased mucosal blood flow
-mucosal ischemia
What are the clinical signs of acute gastritis?
-often mild and self-limiting
-sudden onset of vomiting
-possible hematemesis
-possible melena
-possible anemia
How is acute gastritis diagnosed?
-typically determined from history
-want to confirm no evidence of gastric outflow obstruction
What are the treatment options for acute gastritis?
-treat underlying cause if possible
-small, frequent feedings with easily digestible diet
-IV fluids if severe
-antibiotics if concerned about translocation
-acid suppressants if presence of hematemesis
-anti-emetics once obstruction is ruled out
When should acid suppressants be considered?
-hematemesis
-melena
-esophagitis
-ulceration
What are the characteristics of histamine-2 receptor antagonists?
-competitive inhibition of H2 receptor on parietal cells
-reduces gastric acid secretion
-less effective than proton pump inhibitors
What are the characteristics of proton pump inhibitors?
-irreversibly block proton pumps in parietal cells
-more effective in increasing gastric pH than H2 receptor antagonists
What are the characteristics of chronic gastritis?
-chronic inflammatory changes within gastric mucosa with clinical signs of gastritis
-etiology often not determined
-can occur with stomach worms, chemicals, antigens, drugs
-can have eosinophilic, lymphoplasmacytic, hypertrophic or granulomatous gastritis
What are the clinical signs of chronic gastritis?
-chronic vomiting
-decreased appetite and weight loss
-melena
-hematemesis
What are the diagnostic steps for chronic gastritis?
-rule out extra-GI causes
-rule out stomach worms
-abdominal imaging
-endoscopy
-histopathology
What is the treatment for chronic gastritis?
-treat underlying disease
-consider cytoprotective agents
-diet trial with easily digestible/low fat diet OR hydrolyzed, low protein diet
-may require immunosuppressants
What are the possible etiologies of gastric ulceration?
-any cause of acute or chronic gastritis
-NSAIDs or corticosteroids
-endocrine dz/hypoadrenocorticism
-systemic dz
-extra-GI neoplasia/mast cell tumors
-gastric neoplasia
What are the clinical signs of gastric ulceration?
-vomit with partially digested or fresh blood (hematemesis)
-melena
-abdominal pain
-anorexia +/- weight loss
How is gastric ulceration diagnosed?
definitive:
-endoscopic or surgical visualization
suspicion:
-gastric ultrasound that shows thickening, loss of mucosa, or gas tracking
-increased BUN with normal creatinine
-hematemesis and/or melena
What is the treatment for gastric ulceration?
-treat underlying cause
-treat hypovolemia
-blood transfusion
-acid suppressants
-cytoprotective agents
-surgery if perforation occurs or if medical management fails
What are the characteristics of sucralfate?
-cytoprotective
-basic aluminum salt of sulfated disaccharide
-given as a slurry
-can inhibit absorption of other drugs
What are the characteristics of misprostol?
-cytoprotective
-can cause significant GI distress
-synthetic prostaglandin; should not be prescribed to pregnant patients or patients with pregnant owners
What are the characteristics of pyloric stenosis?
-hypertrophy of the circular muscle fibers in pylorus reduce luminal diameter
-most commonly seen in brachycephalic dogs and siamese cats
What are the clinical signs of pyloric stenosis?
-vomiting following ingestion of solid food
-possible gastric distension
-weight loss
How is pyloric stenosis diagnosed?
-endoscopic exam
-diffuse thickening of pylorus on ultrasound
-serum gastrin in older dogs
What is the treatment for pyloric stenosis?
-surgery; pyloromyotomy or pyloroplasty
-low fat, low fiber canned diet or slurry
Which GI neoplasms are most common in dogs and cats?
cats: lymphoma
dogs: adenocarcinoma
How is GI neoplasia diagnosed?
-ultrasound +/- endoscopy or laparotomy
-FNA
-histopathology
How is GI neoplasia treated?
surgical resection and/or chemotherapy
