Vomiting in Small Animals Flashcards
What is the generic ‘diagnostic approach’ which we can apply to vomiting cases?
Problem
System
Location
Lesion
What might owners confuse with vomiting?
Regurgitation
Gagging
Coughing
What are the phases of vomiting?
Nausea phase
Retching
Vomiting
What happens during the nausea phase of vomiting?
- Salivation and sensation of nausea
- Reduced gastric tone
- Reverse peristalsis
This results in depression, hypersalivation and repeated swallowing
What is meant by the term anti-peristalsis?
Proximal duodenum emptying back into the stomach - moving in the wrong direction.
What happens during the vomiting phase?
- Glottis closes
- Breath is held mid inspiration
- Abdominal wall muscle contraction
- Chest held on fixed position
- Lower oesophageal sphincter and oesophagus relax
- Gastric contents ejected
Why does the glottis close during vomiting?
Prevents aspiration of vomitus
How is the intra abdominal pressure increased during vomiting?
Holding breath,
Chest held in fixed position,
Contraction of abdominal muscle.
How can the CVRS be affected by vomiting?
Cardiac rhythm disturbances - arrhythmias
What is a potential GI effect of vomiting?
Changes in colonic motility - diarrhoea
Physiology of vomiting:
Pharyngeal stimulation
Pharyngeal stimulation — CNIX —> Nucleus tractus solitarius —> Programmed vomiting response vomiting centre Medulla Oblongta.
Physiology of vomiting:
Gastric irritation
Gastric mucosa — CNX —> Nucleus tracts solitarus —>Medulla oblongata
What is the area postrema ?
A medullary structure not protected by BBB (privileged) therefore can act as a sensor for circulating chemicals in blood.
Physiology of vomiting:
Drugs (opiates and chemo), Uraemia (renal failure), radiation
Circulating chemicals sensed by chemoreceptors in AREA POSTREMA —> Nucleus tractus solitaries —> MO vomiting centre
Physiology of vomiting:
Pain, anticipation
Higher centres : diencephalon and limbic system —> MO vomiting centre
Physiology of vomiting:
Motion/ vertigo, middle ear disease
Labyrinth —> cerebellum —> MO vomiting centre
How can antihistamines help with vomiting?
Act on chemoreceptor trigger zone (area postrema)
Act on vestibular system
How can phenothiazine help with vomiting?
Act on vestibular system,
Act on vestibular system
Act on vomiting centre of MO
How can NK1 receptor antagonists help vomiting?
Act on CRTZ, MO and vestibular system
Act on peripheral receptors
How can anticholinergic drugs help with vomiting?
Act on vestibular system and peripheral receptors
What is regurgitation ?
Passive process - no coordinated movements
Facilitated by gravity when head and neck are held down
What can induce/exacerbate regurgitation ?
Alterations in food consistency
Exercise
Excitation
How could you use behaviour to distinguish between nausea and regurgitation?
Nausea and salivation
How could you use the pH of the vomitus to determine whether vomiting or regurgitation had taken place?
Acidic pH is more likely to be vomiting