Understanding Nausea and Vomiting-15 Flashcards
What is Vomiting/Emesis and why do we need it?
Defined as the forceful expulsion of gastric contents.
Controlled by the vomiting centre.
Physiological response to remove toxic substances – often life saving!!
What are the physiological causes of Vomiting
Ingestion of toxic substances
Vestibular system – motion sickness
Cranial nerve – irritation of pharynx
Vagal & ENS – irritation of GIT
What and where is the vomiting centre?
Located in the medulla
Input from area postrema / chemoreceptor trigger zone
Input from other brain regions involved depending on the stimulus
- pain, light, smell
- memory, fear
- movement
What is the regions of the brain that are not protected by the BBB.
The circumventricular organs
What are the phases of emesis.
Stomach squeeze and antiperistalsis
Contraction of diaphragm and abdominal muscles
LES relaxation
Respiration stops
Soft palate and closure of glottis
Cascade of vomit.
When would emetics be useful and what are examples
Would only be useful in emergency situations after ingestion of a toxin.
Salt or mustard powder in water.
What are the receptor systems underlying emesis.
CTZ
D2 & 5-HT3
Vomiting Centre
mACh
Vestibular nuclei
mACh & H1
Visceral afferents
5-HT3
Clinical uses of anti-emetics
Morning Sickness
Motion Sickness
Cytotoxic Chemotherapy drugs
Radiation Therapy
OTC anti-emetics for travel sickness
CINNARIZINE
- an antihistamine (H1)
PROMETHAZINE (Avomine®)
- an antihistamine (H1)
- weak mAch antagonist
What are some other commonly used anti emetics
Hyoscine – a mACh antagonist
Ondansetron – a 5-HT3 antagonist
- used to reduce nausea & vomiting during cancer treatment, post-operative N&V etc
Complimentary therapies such as Motion sickness bands and ginger.
What is hyperemesis and what is the treatments.
Excessive nausea and vomiting during pregnancy.
Treated with anti-emetics, vitamins, steroids, IV-Fluids
