Nausea and vomiting Flashcards
Can stimulating the back of the throat initiate the vomit reflex?
YES - Gag reflex activated
Can Noxious chemicals initiate the vomit reflex?
YES - Chemoreceptor Trigger Zone and Area Postrema Activated!
Can distension or irritation of the stomach or duodenum cause vomiting?
YES via mechanoreceptors / chemoreceptors (Noxious chemicals!)
Can rotation or acceleration of the head cause the vomit reflex to be triggered?
Yes!
-Dizziness
-Motion sickness
-Vestibular apparatus in inner ear feeding
What is a serious issue which can cause Nausea and Vomiting?
Elevated intracranial pressure - haemorrhage
Where is the area postrema located?
Adjacent to the 4th ventricle
What are the capillaries like in the area postrema?
Fenestrated - they have gaps that things can pass through to allow function NO BBB
What is the function of the area postrema?
Samples blood to detect noxious chemicals, such as bacterial toxins, poison and drugs!
What coordinates the motor side of the vomiting reflex?
The NTS
How do dopamine agonists have a pro-emetic effect?
By stimulating D2 receptors in the CTZ/AP
(Apomorphine!)
What is the input from the GI tract in vomiting?
1) detection and stretch
2) 5-HT out
3) vagal afferent arteriole info to NTS
4)5-HT released systemically
What transports the signal from the periphery to the CNS?
Vagal afferents
What are the autonomic responses in vomiting?
-Increased salvation
-Sweating
-Cutaneous vasoconstriction = pale skin
- Increased HR
- Retrograde contraction of small intestine
- Relaxation of the stomach, oesophagus and oesophageal sphincters
What are the somatomotor responses in vomiting?
1) Contraction of the diaphragm
2) closure of the glottis
3) Closure of nasal cavities
4) Strong contraction of the diaphragm and abdo muscles
5) Pressure forces stomach contents to move upwards and ejected via the mouth
The vestibular system - muscarinic - anti-muscarinic. what neurotransmitter stimulates this in vomiting?
Acetylcholine
What neurotransmitter plays a role in motion sickness and n&v?
Histamine
What neurotransmitter is released by chromaffin cells and sends info to the NTS then the drugs acting here in the peripheral and central nervous system?
5-HT
What neurotransmitter has a direct emetic effect and is also found in the gut?
Dopamine
What neurotransmitter is a neurokinin receptor?
Substance P
What neurotransmitter stimulates opioid receptors giving an anti-emetic effect?
Enkephalins
Hyoscine helps with motion sickness and has anti-muscarinic side effects includng drowsiness as it blocks the PNS, what type of drug is this?
Muscarinic antagonist - works on vestibular pathways
Cinnarizine, Cyclizine, Promethazine all help with motion sickness but can make a patient drowsy, and assert anti-muscarinic side effects what class of drug are they?
H1 Antagonists
Ondanestron, Granisetron and Palonosetron are used for N&V associated with chemotherapy, radiotherapy and anaesthesia and can prolong QT interval, what class of drug is this?
5-HT3 antagonists
Phenothiazines such as prochloperazine and chlorpromazine, what is there MOA?
Dopamine antagonists: block multiple receptors (H1 and mAChRs) as well as D2 receptors
Metoclopramide and domperidone are potent anti-emetics what class of drug is this?
D2 antagonist
Does domperidone cross the BBB?
No - it works at the CTZ and blocks D2 receptors, doesn’t enter brain
What can D2 antagonists cause if they cross the BBB?
Hyperprolactinaemia! - as they inhibit the dopamine receptors in the brain which make prolactin.
What type of drug is Substance P (Aprepitant and Fosaprepitant)
NK1 Antagonist
*Given as an adjunct
What class of drug is blocked by naloxone so the mechanism of action involves opioid receptors, given for N&V from chemo, and can cause patients to be drowsy?
CB1 agonists - Nabilone
What anti-emetic can cause Psychotic side effects?
Nabilone
What type of steroid can be given for nausea and vomiting in chemotherapy?
Dexamethasone
What are the common GI causes of vomiting?
-Gastro-enteritis’s
-Peptic ulceration
-Appendicitis
-Gastric carcinoma
-Infection (V.common)
What are the common Organic diseases that cause vomiting?
-Renal failure (uraemia),
-Diabetic ketoacidosis, -Myocardial infaraction!
What CNS affects can cause vomiting?
-Migraines
-Meningitis
-Vestibular disease (Menieres)
Does motion sickness happen in children less than 1?
Rarely happens as the labyrinth isn’t functional
What age group are most vulnerable to motion sickness?
3-12
How do Opiates and levodopa cause N&V?
Mimic the action of neurotransmitters,
How do 5-HT3 re-uptake inhibitors cause N&V?
Cause a change in levels of a transmitter
What does activation of the abdominal afferent system (Peripheral), do?
Delay gastric emptying, or direct activation of mucosal afferent system
What is Meniere’s disease?
Disorder of the inner ear, includes having excess fluid in the labyrinth canals (hydrops)
What can the incapicitating attacks of Meniere’s disease cause?
-Giddiness, vertigo, N&V,
-Hearing loss
-Tinnitus
If a patient with vertigo has N&V, what should be do?
Refer
What is it when a patient has the sensation of rotation or spinning?
Vertigo
What is the condition where Ca2+ crystals move and displace therefore causing loss of balance?
Benign Paroxysmal Positional Vertigo (BPPV)
What drugs are vestibular toxic?
Aminoglycosides (Gent), Anticonvulsants, Furosemide, NSAIDs, Quinine
When is the peak time for morning sickness?
10-14 weeks
what causes morning sickness?
High levels of hCG
What is Hyperemesis Gravidarum?
-Severe, persistent N&V during pregnancy
-Weight loss, dehydration, acidosis, ketosis
*if untreated can be fatal!
Why do we treat N&V?
-V unpleasant
-Dehydration
-Renal impairment
-Electrolyte abnormalities
-Weight loss
If a patient has projectile vomiting, sour smelling vomit or blood in vomit what should we do?
*Pyloric stenosis possible = REFER
If we are worried about dehydration what should we do?
REFER
If a patient has severe diarrhoea lasting a long time what should we do?
REFER
If a patient has lost weight, what should we do?
REFER
If a patient has abdo pain, what should we do?
REFER = possible, appendicitis, biliary colic, renal colic, hernias
If a patient is experiencing dizziness alongside N&V, what should we do?
REFER = Meningitis, head injury, Meniere’s disease!
How long does it take for H1 receptor antagonists to work?
Act within 2 hours
What ‘salt’ is longer acting regarding to H1 antagonists?
Theoclate salts are longer acting than hydrochloride
What anti-emetic is contraindicated in glaucoma and urinary retention?
Hyoscine
Prochlorperazine is rapidly absorbed, what class is this?
D2 receptor antagonist
What extra pyramidal side effects can Prochlorperazine cause?
Parkinson’s like!
What anti-emetic has pro-kinetic properties, therefore stimualtes gastric emptying and is more effective in GI and biliary disease?
Metoclopramide
What does Metoclopramide do?
Block D2 receptors and some 5HT3 acts centrally and peripherally
How long does it take for metoclopramide to peak?
after 2 hours
What is the MHRA warning regarding metoclopramide?
MAX DOSE = 30mg for max of 5 days!
What D2 receptor antagonist doesn’t cross the BBB?
Domperidone
Where is 5HT3 receptors located?
Peripherally on vagal nerve endings and vomiting centre
What class of anti-emetics have less cardio / CNS side effects?
5HT3 receptor antagonists
What type of Anti-emetic is used for chemo induced N&V?
NK1 receptor antagonists - as they block Neurokinin-1 receptors
