Nausea and Vomiting Flashcards
What is nausea?
The unpleasant urge to vomit
What is vomiting?
The forceful expulsion of the stomach contents through the mouth/nose
What is retching?
Repetitive peistalsis of the stomach and oesophagus without vomiting
What is regurgitation?
The effortless movement of swallowed food contents back into the mouth
What occurs during vomiting?
Forceful inspiration
Reflex closure of the glottis
Elevation of the soft palate
Closure of airways and nasal passages
Where is vomiting coordinated?
The Vomiting centre (VC) of the medulla
What contents are involved in vomiting?
The contents of the stomach and the small intestine
What is the sequence of events in vomiting?
Suspension of intestinal slow wave activity > Retrograde contractions from ileum to stomach > Suspension of breathing> Relaxation of LOS contraction of diaphragm and abdominal muscles> Ejection of gastric contents through open UOS
What autonomic/somatic symptoms precede vomiting?
Salivation
Sweating
Elevated heart rate
Nausea
What are the 2 most important things that stimulate vomiting?
Presence of toxic materials in the gut Systemic toxins (e.g. drugs)
What cells do the stimuli stimulate?
Enterochromaffin cells in the mucosa
Enterochromaffin cells release what mediators and what does this result in?
5-HT and Substance P
The depolarization if sensory afferent terminals in mucosa
Where do action potentials in the vomiting cycle occur from?
The mucosa
Where do the action potentials move to?
CTZ - chemo receptor trigger zone
NTS - Nucleus tractus solitarius
What do the CTZ and NTS do?
Co-ordination of the vomiting
what is the population of portpatrick and what are their names?
5
Joanne, Billy, Elaine, Gillian McKeith and Ozzy
How can MI cause vomiting?
Intense pain can stimulate vomiting
Stimulation of………..
What is anticipatory vomiting?
Patients feeling sick when seeing the hospital or in advance of chemotherapy
CNS stimulation
What causes motion sickness?
The difference between the stimuli received from the eyes and the rest of the body
Where is the motor output that coordinates vomiting located?
The brainstem - vomiting centre
What is the vomiting centre?
A group of interconnected neurones within the medulla that receives input from the NTS
What are the 3 types of motor output?
Vagal efferents
Somatic motor neurones
Autonomic/somatic efferents
What do vagal efferents result in?
Shortening of oesophagus
Relaxation of stomach
Retrograde contraction of the small intestine
What do somatic motor neurones do?
Contraction of the anterior abdominal muscle
Contraction of the diaphragm
What do autonomic/somatic efferents do?
Increased heart rate
Increased salivation
Cold Skin
Constriction of bladder and anus
What are the consequences of sever vomiting? (5)
Dehydration
Loss of gastric protons and chloride (Hypochloraemic metabolic alkalosis)
Hypokalaemia
Mallory-Weiss tear
Aspiration of the vomitus into the air passage and lungs
What is a Mallory-Weiss tear?
Tear of the inner mucosal walls of the oesophagus
Results in reddish streaks of fresh blood in the vomitus
What drugs can cause nausea and vomiting?
Cancer chemotherapy Radiotherapy General Anesthetics Dopamine receptor stimulants Morphine and other opiate analgesics Cardiac glycosides Drugs that enhance the function of 5HT
What do 5HT3 receptor antagonists (Setrons) used for?
Antiemetic drugs
Suppress chemotheraphy and radiation-induced emesis and post-operative nausea and vomiting
Block peripheral and centeral 5HT3 receptors
What do 5HT3 receptor antagonists do?
Reduce acute nausea, retching and vomiting
When are 5HT3 receptor antagonists less effective?
During subsequent treatments
What improves the action of a 5HT3 receptor antagonist?
Addition of a corticosteroid and a neurokinin receptor antagonist
What are muscarinic acetylcholine receptor antagonists and what are they used for?
Anti-sickness drugs
For motion sickness
E.g. Hyosine/Scopolamine
What is the mechanism of Muscarinic ACH receptor antagonists?
Block ACH receptors at multiple locations at affector organs innervated by the parasympathetic nervous system
Causes inhibition of the GI movements and relaxation of the GI tract
What are 2 examples of a H1 receptor antagonist?
Cyclizine
Cinnarizine
What are H1 receptor antagonists used for?
Prophylaxis and treatment of:
motion sickness and acute nausea
vomiting caused by stomach irritants
What is the mechanism of H1 receptor antagonists?
Blockade of H1 receptors in the vestibular nuclei and NTS
What are the side effects of H1 receptor antagonists?
CNS suppression
What are Dopamine receptor antagonists?
Used for treatment off drug induced vomiting
What are 2 examples of Dopamine receptor antagonists?
Domperidone
Metoclopramide
What is the mechanism of action of Dopamine receptor antagonists?
Block Dopamine D2 and D3 receptors in the CTZ
Exert a prokinetic action on the oesophagus, stomach and small intestine
