Gastroenterology - Vomiting Flashcards
What are the vomiting phases?
Phase 1 - nausea
Phase 2 - retching
Phase 3 - forceful expulsion
What occurs during phase 1 of vomiting?
Nausea
- hiding or seeking attention
- ptyalism, yawning, shivering, tachycardia, pallor
What occurs during phase 2 of vomiting?
Retching
- abdominal muscles, chest wall, and diaphragm contract
- deep inspiratory movements
- respiratory center inhibited
What occurs during phase 3 of vomiting?
Forceful Expulsion
- force arise from contraction of abdominal muscles and diaphragm
- stomach, esophagus, and sphincter relax
Describe the mechanism of “motion sickness”
inner ear/labyrinth stimulation
> dopamine and serotonin released from CRTZ activation
> Ach released from emetic center
What is stimulated with chemo-agent induced emesis?
5-HT3 and CRTZ
How does uremia cause emesis?
- decreased gastrin clearance > ulcers and gastritis
- toxins crossing BBB > stimulate central and peripheral receptors
- activates CRTZ via dopaminergic receptors
Describe the physiological pathway of emesis
- activation of chemoreceptors and mechanoreceptors
- stimulation of visceral afferent receptors
- direct stimulation of cerebral cortex and limbic system, or, vestibular system stimulation
What is the CRTZ?
Chemoreceptor Trigger Zone
- stimulated by vestibular system
- free nerve endings bathed in CSF
How does intestinal inflammation stimulate emesis?
direct afferent input to vomiting center
What are the effects of opioids?
stimulation of CRTZ
increased vestibular sensitivity
gastric stasis
impaired intestinal motility and constipation
What are the possible differentials for acute vomiting?
- toxin
- dietary indiscretion
- medication
- diet change
- foreign body
- pancreatitis
- Addisonian crisis
- acute manifestation of chronic disease
What are the possible differentials for chronic vomiting?
- intermittent foreign body
- organ failure/dysfunction
- chronic pancreatitis
- primary gastric disease
- primary small intestinal disease
- atypical Addisons, hyperthyroidism
What tests are included in the “Big 4”?
PCV
Total solids
Blood glucose
AZO stick
What diagnostics can be done for the vomiting patient?
- CBC, Chem, UA
- fecal
- coagulation profile
- baseline cortisol
- PLI to assess for pancreatitis
- radiographs, ultrasound, endoscopy
What should be looked for on an abdominal radiograph of a vomiting patient?
- GDV
- GI or urinary obstruction
- large mass
- pyometra
- effusion
What should be looked for on a chest radiograph of a vomiting patient?
- aspiration pneumonia
- dilated esophagus
- diaphragmatic hernia
What should be looked for on an abdominal ultrasound of a vomiting patient?
- obstruction
- large or small mass lesions
- alteration in lining of stomach or SI
- pancreatitis
- other organ problems
What is the purpose/benefit of doing an endoscopy on a vomiting patient?
- visual exam of esophagus, sphincters, stomach, and duodenum
- remove foreign bodies
- biopsy tissue
What therapy should be done for an acutely vomiting, but not ill, patient?
- medical: fluid therapy, diet modification, and time
- no water for 6 hours, then small frequent amounts
- if no vomiting, small meals every 4-6 hours
What therapy should be done for acute or chronic vomiting patient that is ill?
- IV fluids
- antacids, mucosal protectants
- pain management
- nutritional support
Which fluids are used for maintenance?
Normosol
Plasmalyte
LRS
Sodium Chloride 0.9%
What is the mechanism of histamine receptor antagonists?
Name some drugs
- affect gastric parietal cell receptors
- limit acid secretion with mild to little effect on pH
- Famotidine, Ranitidine, Cimetidine
What is the mechanism of proton pump inhibitors?
Name some drugs
- inhibits transport of hydrogen ions into the stomach
- inhibits the hepatic cytochrome P-450 mixed function oxidase system
- Pantoprazole, Omeprazole
What is the main mechanism of action of antiemetic drugs?
block/compete with neurotransmitters at the receptor sites associated with emesis
What is Scopalamine?
What does it do?
M1-Cholinergic receptor antagonist
- crosses BBB
- causes excitement in cats
What are possible side effects of M1-Cholinergic receptor antagonists?
sedation and hypotension
Name some M1-Cholinergic receptor antagonists
Phenothiazines
Propantheline and Isopropamide
Are Histamine antagonists used in cats?
Why or why not?
no because cats do not have histamine receptors on their CRTZ
What are some histamine antagonists?
Diphenhydramine
Meclizine - vestibular disease
Cyproheptadine - appetite stimulation
What type of drug is Metoclopramide?
What are the effects and side effects?
- D2-Dopaminergic antagonist
- stimulates movement of distal esophagus
- 5-HT3 antagonist and 5-HT4 agonist
- side effects: constipation and mentation change
Is Metoclopramide more effective in dogs or cats? Why?
more effective in dogs
- cats have fewer dopamine receptors
What type of drugs are Ondansetron and Dolasetron?
What are their side effects?
- 5-HT3 Serotonin antagonists
- effect receptors in GIT and CRTZ
- side effects: dry mouth, fatigue, constipation
What type of drug is Maropitant?
What is the mechanism of action?
What are the side effects?
- NK-1 receptor antagonist
- competes with substance P
- s/e: ataxia, anorexia, diarrhea, injection soreness, and bradycardia with high dose
Describe the action of Sucralfate/Carafate
- stimulates PG E2
- reacts with HCl to form a paste that sticks to ulcers
- inactivates pepsin and binds bile acids
What is Misoprostal?
What are does it do?
- prostaglandin analog
- treat/prevent gastric ulcers
- direct action on parietal secretion of gastric acid
What is Octreotide?
What does it do?
- stomatostatin analog
- treatment of insulinomas and gastrinomas
What are some examples of prokinetics?
- Metoclopramide
- Cisapride
- Ranitidine
- Erythromycin
What is cyproheptadine?
What is it used for?
- H1 receptor blocker
- serotonin antagonist
- appetite stimulation
What is a tricyclic antidepressant?
What is it used for?
- 5-HT3 antagonist
- increases NE and appetite
