Nausea & Vomiting Flashcards
Define nausea:
unpleasant feeling of the need to vomit associated with autonomic symptoms (pallor, sweating, tachy, salivation)
Define retching:
rhythmic laboured spasmodic movements of the diaphragm and ab muscle
Define vomiting:
forceful propulsion of gastric contents through the mouth
What are the different mechanisms that can cause nausea and vomiting?
chemoreceptor trigger zone
cerebral cortex
vestibular cortex
gut
What are the different causes of nausea and vomiting?
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
Where do the different causes of N+V act and by what mechanism ?
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
What are commonly used medications for N+V?
metoclopromide cyclizine haloperidol ondansetron levomepromazine
What are the symptoms of gastric stasis ?
epigastric fullness early satiety large vol vomits (projectile) hiccups regurgitation nausea usually quickly relieved by vomiting
What are the contributing factors gastric stasis?
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
How is gastric stasis treated?
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)
How does metoclopromide work andwhat are the side effects?
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
What are the contributing factors to GI or visceral irritation?
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
How do you treat GI or visceral N+V?
Tx: address cause
5HT3 antagonists = ondansetron - 1st line in chemo related nausea
anti-cholingeric = cyclizine
What is ondansetron?
5HT3 R antagonist
commonly used post-op, chemo and radiotherapy
- costly and has SE: constipation, OTc prolongation
What is cyclizine?
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
Why can’t cyclizine be prescribed alongside metoclopromide?
cyclizine slows gastric transit due to antimuscarinic effects==> blocking the effects of metoclopromide
What are the key features of chemical or metabolic N+V?
constant nausea
less or variable vomiting
What is the mechanism underlying chemical or metabolic N+V?
Stimulation of CTZ: Dopamine2 and 5HT3 R
- chemical drugs: opioids, abx, digoxin, NSAIDs, SSRIs, chemo
- metabolic: renal/liver failure, hypercalcaemia of malignancy, hyponatraemia, sepsis
What dopamine D2 antagonists are there for treating chemical/metabolic N+V?
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
What 5HT3 antagonist are there for treating chemical/metabolic N+V?
ondansetron
What are the characteristics of raised ICP?
sx worse in morning?
headache
nausea and vomiting
How does the mechanism fo raised ICP cause n+v?
stimulation of vomiting centre
- histamine -1 and AChm receptors
How do you treat N+V due to raised ICP?
anti-histmiane and anti-cholingeric agents
= cyclizine
depends on the cause though e.g. ?SOL-?steroids ?radiotherpay
What are the characteristics of motion sickness?
vomiting on movement
dizziness
What is the mechanism underlying motion sickness?
stimulation of vestibular system - H1 and ACHm R
- contributing factors: stimulation of vestibular system, opioids can increase vestibular sensitivity, ? intracerebral cause
What is the treatment for motion sickness?
anti-histmian and anti-cholingeric agents: cyclizine
What drug combinations should be avoided?
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
