Nausea & Vomiting

Question 1

Define nausea:

Answer 1

unpleasant feeling of the need to vomit associated with autonomic symptoms (pallor, sweating, tachy, salivation)

Question 2

Define retching:

Answer 2

rhythmic laboured spasmodic movements of the diaphragm and ab muscle

Question 3

Define vomiting:

Answer 3

forceful propulsion of gastric contents through the mouth

Question 4

What are the different mechanisms that can cause nausea and vomiting?

Answer 4

chemoreceptor trigger zone
cerebral cortex
vestibular cortex
gut

Question 5

What are the different causes of nausea and vomiting?

Answer 5

drugs=> analgesia, abx, iron, digoxin, antidepressants
metabolic => hypercalcaemia, renal failure, hyponatraemia
GI => gastric irritation, distension, bowel obstruction, oedematous gut, constipation
other=> raised ICP, vestibular disturbance
toxic=> radiotherapy, chemo
psychological => fear, anxiety

Question 6

Where do the different causes of N+V act and by what mechanism ?

Answer 6

CTZ=> opioids, hypercalcaemia, chemo, toxins –> serotonin and dopamine

cerebral cortex=> anxiety, rasied ICP, hyponatramia, signs and smells –> histmaine an serotonin

vestibular cortex => movement –> muscarine receptors and histamine

gut => radio, cytotoxics, drugs, toxins, irritants, intestinal distension –> serotonin and dopmaine

vomiting centre= muscarinc, histmaine and serotonin

Question 7

What are commonly used medications for N+V?

Answer 7

metoclopromide
cyclizine 
haloperidol
ondansetron 
levomepromazine

Question 8

What are the symptoms of gastric stasis ?

Answer 8

epigastric fullness
early satiety 
large vol vomits (projectile)
hiccups
regurgitation 
nausea usually quickly relieved by vomiting

Question 9

What are the contributing factors gastric stasis?

Answer 9

stomach emptying problems e.g. autonomic - gastritis, peptic ulcer
compression of gastric outflow e.g. tumour, hepatomegaly
drug side effects e.g. anti-cholingics, opioids

Question 10

How is gastric stasis treated?

Answer 10

reduce vol oral intake - little and often
reduce gastric secretions - H2 antagonist (ranitidine)
or prokinetic agents = dopamine D2 antagonist (metoclopromide, domperidone - careful giving these to PD patients)

Question 11

How does metoclopromide work andwhat are the side effects?

Answer 11

dopamine D2 R antagonist and serotonin agonist
- acts peripherally but can cross BBB
- prokinetic- useful in delayed gastric emptying
- usually 10mg TDS PO
side effects: risk extrapyraidal SE across BBB, abdominal cramps (caution in bowel obstruction)
risk in young pts (<20) of oculogyric crisis

Question 12

What are the contributing factors to GI or visceral irritation?

Answer 12

stimulation of vagus/Gut 5HT3 receptors

• irritation - pharyngeal irritation = tumour, sputum, candida
• stretch R of GI or GU tract= constipation, bowel obstruction, chemo
• stretch R of visceral capsules = hepatomegaly

Question 13

How do you treat GI or visceral N+V?

Answer 13

Tx: address cause
5HT3 antagonists = ondansetron - 1st line in chemo related nausea
anti-cholingeric = cyclizine

Question 14

What is ondansetron?

Answer 14

5HT3 R antagonist
commonly used post-op, chemo and radiotherapy
- costly and has SE: constipation, OTc prolongation

Question 15

What is cyclizine?

Answer 15

centrally acting
anti-muscarinc and anti-histamine activity
for: motion sickness and vomiting secondary to raised ICP
good 1st line anti-emetic in hosp
SE: dry mouth, constipation, sedation (due to antimuscarinic effect)
avoid its use in HF

Question 16

Why can’t cyclizine be prescribed alongside metoclopromide?

Answer 16

cyclizine slows gastric transit due to antimuscarinic effects==> blocking the effects of metoclopromide

Question 17

What are the key features of chemical or metabolic N+V?

Answer 17

constant nausea

less or variable vomiting

Question 18

What is the mechanism underlying chemical or metabolic N+V?

Answer 18

Stimulation of CTZ: Dopamine2 and 5HT3 R

• chemical drugs: opioids, abx, digoxin, NSAIDs, SSRIs, chemo
• metabolic: renal/liver failure, hypercalcaemia of malignancy, hyponatraemia, sepsis

Question 19

What dopamine D2 antagonists are there for treating chemical/metabolic N+V?

Answer 19

Haloperidol

• works at CTZ
• commonly used in palliative care
• SE: extrapyramidal SE, OTc prolongation, sedation

levomepromazine

• broad spectrum anti-emetic
• used as antipsychotic but effective for nausea
• used in palliative care e.g. bowel obstruction
• SE: sedation, postural hypotension

Question 20

What 5HT3 antagonist are there for treating chemical/metabolic N+V?

Answer 20

ondansetron

Question 21

What are the characteristics of raised ICP?

Answer 21

sx worse in morning?
headache
nausea and vomiting

Question 22

How does the mechanism fo raised ICP cause n+v?

Answer 22

stimulation of vomiting centre

- histamine -1 and AChm receptors

Question 23

How do you treat N+V due to raised ICP?

Answer 23

anti-histmiane and anti-cholingeric agents
= cyclizine
depends on the cause though e.g. ?SOL-?steroids ?radiotherpay

Question 24

What are the characteristics of motion sickness?

Answer 24

vomiting on movement

dizziness

Question 25

What is the mechanism underlying motion sickness?

Answer 25

stimulation of vestibular system - H1 and ACHm R
- contributing factors: stimulation of vestibular system, opioids can increase vestibular sensitivity, ? intracerebral cause

Question 26

What is the treatment for motion sickness?

Answer 26

anti-histmian and anti-cholingeric agents: cyclizine

Question 27

What drug combinations should be avoided?

Answer 27

metoclopromide/domperidone and cyclizine = block each other’s effects

IV metoclopromide and IV ondansetron = risk of serious cardiac arrhythmias

Long term use of concurrent QTc prolonging drugs

Avoid long term use of metoclopromide/domperidone as increased risk of extra-pyramidal SE