Mechanisms of nausea and vomiting

Question 1

4 causes of nausea and vomiting

Answer 1

Reduced gastric motility
Chemically mediated
Raised intra-cranial pressure
Vestibular

Question 2

Reduced gastric motility
-causes
-receptors
-antiemetics you can use

Answer 2

Causes
-opioid
-ileus

5HT4 - seretonin
D2 - dopamine

Metoclopramide
But don’t use when we don’t want to bowel to move
-BO, GI perforation, immediately after GI surgery

Domperidone - doesn’t cross BBB

Question 3

Chemically mediated
-causes
-receptors
-antiemetics you can use

Answer 3

Causes
-metabolic - renal, liver failure, hypercalcemia of malignancy, electrolyte imbalances
-drugs - opioids, ABx, digoxin, NSAIDs, SSRIs, chemotherapy

Treat the reversible

D2 - dopamine antagonist
-Haloperidol
-Levomepromazine

5HT3 antagonist
-Ondansetron

Question 4

Motion sickness/vestibular
-causes
-receptors
-antiemetics

Answer 4

Motion related
Brain mets, CVA
Opioid - increase vestibular sensitivity

Ach

H1
1st line - cyclizine for vestibular

Refractory vestibular causes alts
-metoclopramide, prochloperazine

Question 5

Increased ICP
-causes
-receptors

Answer 5

Cerebral mets

Symptoms worse when lying down
Headache, N/V

H1
1st line - Cyclizine

Steroids - Dexmethasone

Ach

RT

Question 6

Route of administration

Answer 6

PO preferable unless
-vomiting
-malabsorption issues
-severe gastric stasis

IV used if IV access available