Dysphagia, vomiting, anti-emetics Flashcards
What are the stages of swallowing?
oral stage
pharyngeal stage
oesophageal stage
What are 2 types of dysphagia?
oropharyngeal - unable to transfer food bolus from mouth to upper oesophagus
oesophageal - sensation of food sticking in throat or chest after swallowing
Causes of oropharyngeal dysphagia
neuromuscular disorders:
- stroke
- head injury
- brainstem tumours
- MND
- muscular dystrophies
- MS
- Parkinson’s disease
- MG
mechanic obstruction:
- oropharyngeal tumours
- pharyngeal pouch
- cricopharyngeal bar
Causes of oesophageal dysphagia
dysmotility:
- achalasia
- hypercontractile oesophagua
- hypertonic lower oesophageal sphincter
- diffuse oesophageal spasm
- scleroderma
mechanical obstruction:
- benign stricture
- malignant stricture
- oesophageal tumour
- oesophageal web
- eosinophilic oesophagitis
- external compression
Investigations for dysphagia
SALT assessment
video fluoroscopy
oesophageal manometry
gastroscopy
What is eosinophilic oesophagitis?
chronic immune-mediated condition
eosinophilic infiltrate of oesophageal epithelium
treatment = swallowed steroids
associated with atopy
2 important areas in medulla that initiate nausea + vomiting
emetic centre
chemoreceptor trigger zone
What are the 5 receptors that may trigger the chemoreceptor trigger zone?
serotonin (5HT3)
histamine (H1)
muscarinic
dopamine (D2)
substance P (neurokinin/neuropeptide)
Ondansetron MOA
5HT3 antagonist
Ondansetron indication
cytotoxic drug induced vomiting
Metoclopramide/prochlorperazine MOA
dopamine antagonist
Metoclopramide indication
opiate induced vomiting
(can worsen CNS symptoms, eg. worsens symptoms in Parkinson’s)
Cyclizine MOA
histamine antagonist
Cyclizine indication
motion sickness
Hyoscine MOA
muscarinic antagonist
Hyoscine indication
motion sickness
Why are dopamine antagonists not useful in motion sickness?
vestibular nucleus contains muscarinic and histamine receptors, not dopamine
Why are dopamine antagonists anti-emetic of choice for opiate-induced nausea and vomiting?
opiates cross BBB and activate chemoreceptor trigger zone
dopamine receptor antagonists also cross the BBB so are the anti-emetic of choice
