PBL 2 Flashcards
what foods/drinks should you avoid with d+v?
fruit juice fizzy drinks greasy food spicy food high fat and sugar foods dairy caffeiene
what meds can be given for diarrhoea?
bismuth subsalicylate (pepto-bismol_ loperamide
what are examples of antiemetic drugs for acute vomiting?
phenothiazines e.g. prochlorperazine antihistamines e.g. cyclizine metoclopramide domperidone ondansetron dexamethasone
how long should you stay off school/work after d+v?
at least 2 days after the last episode
how does bismuth subsalicylate work?
decreases the flow of fluids into the bowel, reduces inflammation and may kill organisms that can cause diarrhoea
what is oral rehydration therapy?
a balanced mixture of electrolyte salts and glucose used to prevent and treat dehydration, especially due to diarrhoea
what is ORT made up of?
sodium chloride, sodium citrate, potassium chloride and glucose.
how does ORT work?
it uses the Na+/glucose cotransport mechanism to passively absorb water across the intestinal mucosa
what are potential side effects of ORT?
vomiting
hyperkalaemia hypernatremia
what are some contraindications of ORT?
shock, severe dehydration, intractable vomiting, coma, acute abdomen, absent bowel sounds, severe renal impairment, visible water retention, hyperkalaemia, chronic heart failure
what is diarrhoea defined as?
loose watery stools 3+ times in 24 hours
whats the difference between acute, persistant and chronic diarrhoea?
acute <2 weeks
persistant 2-4 weeks
chronic >4 weeks
what is inflammatory diarrhoea?
inflammation of GI epithelium usually as a result of invasive pathogens or chronic IBD. usually comes with systemic symptoms too
associated with vomiting and the ingestion of contaminated food
what is non-inflammatory diarrhoea?
can be secretory or osmotic. secretory diarrhoea is where we have increased water + electrolyte secretion and decreased absorption. With osmotic diarrhoea, come ingested nutrients aren’t absorbed so they pull water into the lumen through osmosis
stools are bloody and mucusy, severe abdo pain and fever
what would a cause of diarrhoea be at 6 hours after ingesting food? what about 8-16hrs? or >16 hrs?
<6hrs = staph aureus or bacillus cereus
8-16hrs = clostridium perfringens
>16 hrs = enterotoxigenic E.COli
what are some causes of inflammatory diarrhoea?
salmonella
giardia
c.diff
TB
where is the vomiting centre? what receptors does it have?
in the medulla oblongata
muscarinic receptors
where is the chemoreceptor trigger zone? what receptors does it have?
in medulla oblongata but outside the blood brain barrier so detects blood
dopamine 2 and 5HT receptors
describe the physiology of motion sickness?
problems in the vestibule in the labrynth of the ear causes the vestibulocochlear nerve to send signals to the vestibular nuclei in the pons. it stimulates the histamine 1 and muscarinic receptors which stimulates it, causing a signal to be sent to the CTZ. These receptors are triggered, stimulating the CTZ to send a signal to the vomiting centre to initiate the vomiting reflex
outline the physiology of emesis caused by cytotoxic agents?
enterochromaffin cells release serotonin in response to cytotoxic agents which can stimulate 5HT3 receptors on vagal nerve fibres around the area. This takes the information to the vomiting centre to trigger the vomiting reflex.
whats the pro-dromal phase of the vomiting reflex?
relaxation of gastric muscles followed by small intestinal retrograde peristalsis
whats the ejection phase of the vomiting reflex?
retching and vomiting including expulsion of gastric contents
outline the mechanism of vomiting?
- A deep breath is taken, the glottis is closed and the larynx is raised to open the upper esophageal sphincter. Also, the soft palate is elevated to close off the posterior nares.
- The diaphragm is contracted sharply downward to create negative pressure in the thorax, which facilitates opening of the esophagus and distal esophageal sphincter.
- Simultaneously with downward movement of the diaphragm, the muscles of the abdominal walls are vigorously contracted, squeezing the stomach and thus elevating intragastric pressure. With the pylorus closed and the esophagus relatively open, the route of exit is clear.
what is faeces made up of?
food that could not be digested
bacteria
stercobilin
dead epithelial cells from the lining of the gut
what is the anal sampling mechanism?
The ability of the rectum to discriminate between gaseous, liquid and solid contents is essential to the ability to voluntarily control defecation.
also allows for flatulance to occur without eliminating solid waste
what are the 2 defecation reflexes?
myenteric reflex - increasing peristalsis and propelling stool toward the rectum. This eventually signals the internal anal sphincter to relax and reduce sphincter constriction.
parasympathetic reflex - similar to above but the person can control it
where is bile made and stored?
liver
gallbladder
what is bile made up of?
mostly bile salts and phospholipids
also cholesterol and bilirubin
outlne how bile is formed and taken to the gallbladder?
cholesterol is broken down in hepatocytes by 7 alpha-hydroxylase into 2 primary bile acids; cholic acid and chenodeoxycholic acid
in the intestines some of these primary bile acids get de-hydroxylated into deoxycholic acid and lithocholic acid.
the liver can conjugate the amino acids, glycine and taurine, onto both the primary and secondary bile acids to ultimately give rise to 8 different bile salts
the bile then moves down the hepatic ducts, into the cystic duct and then into the gallbladder
what causes release of bile from the gallbladder?
CCK release by I cells in the small intestine
what secrete biocarbonate rich fluid into the small intestine?
cholangiocytes which line the common bile duct
outline the breakdown of Hb to urobilinogen?
Hb -> heme and iron
Heme oxidase converts heme to biliverdin
biliverdin reductase coverts biliverdin to bilirubin
unconjugate bilirubin enters blood bound to albumin and is taken to the live
uridine glucoronyl transferase conjugate bilirubin - this is more soluble so can be secreted into bile
this bile flows into intestines
bacteria hydrolyse and reduce bilirubin into urobilinogen
what happens to urobilinogen?
most gets oxidised by gut bacteria to stercobilin
some is reabsorbed from the gut into the blood taken to kidneys and converted to urobilin - makes urine yellow
some is taken back to the liver in the enterohepatic circulation
what makes an infectious disease notifiable to public health?
if its on the notifiable list
any infection which presents/could present/could have presented significant harm to human health
any contamination which could/has presented significant harm to human health.
when you find a notifiable disease, at what point should you notify Public Health England?
staright away! do it based on clinical suspicion, do not wait for labs
urgent - within 24 hrs on a phone call
routine - within 3 days written up
what are examples of diarrhoeal diseases which are notifiable to Public Health England?
cholera
typhoid
food poisoning
infectious blood diarrhoea
how do we define an outbreak?
an increase in incidence of a disease above expected levels in a particular location or population in a given time period
the occurrence of a disease in two or more epidemiologically linked individuals, such as those with a confirmed common source of infection.
how do you catch salmonella?
raw meats, eggs or poultry or unpasteurized milk
how do you catch e.coli?
raw meat/contaminated food, ingesting contaminated water
how do you catch campylobacter?
eating raw or undercooked poultry or something that touched it. also from contaminated food/water
how do you catch listeria?
raw vegetables contaminated from soil/manure, contaminated meat, unpasteurised milk. particularly a problem with ready-to-eat foods e.g. pate, cooked sliced meat, moul-ripened soft cheeses, prepepared salads and sandwiches etc
how do you catch clostridium botulinum?
contaminated illicit drugs injected into skin, can get it from foods containing toxins - particulalrly canned food
how do you catch shigella?
direct contact, eating contaminated food and water
how do you catch yersinia?
eating or drinking contaminated food/water
how do you catch giardia?
tiny parasite that causes the diarrheal disease giardiasis. Found on surfaces/soil/food/water contaminated with faeces of infected beings
what does listeria cause?
listeriosis
what does clostridium botulinum cause?
botulism
what does shigella cause?
shigellosis
what does Yersinia enterocolitica cause?
yersiniosis
what is giardia commonly misdaignosed as and why?
IBS as it causes…
stomach cramps, bloating, nausea and bouts of watery diarrhea but in an episodic manner
whats the most common cause of dysentery in the UK?
shigella
whats the most common bacteria causing food poisoning in the UK?
campylobacter
whats the most common cause of gastroenteritis in the UK?
norovirus
what are the main causative organisms that cause traveller’s diarrhoea?
enterotoxigenic Escherichia coli,
Campylobacter jejuni, Shigella spp., and Salmonella spp
how do you acquire cholera?
swallow food or water contaminated with vibrio cholera bacteria
what is typhoid caused by?
salmonella typhi
how do you catch hepatitis E?
from drinking water contaminated with feces from people infected with the virus
