Everything Flashcards
(92 cards)
<p>What is plasma osmolality?</p>
<p>290 mOsm/kg</p>
<p>How do you distinguish between osmotic and secretory diarrhoea?</p>
<p>Calculate osmotic gap:
Faeces sample is taken and levels of Na+, Cl-, K+ and HCO3- are calculated. The remaining value is "unmeasured ions" (the osmotic gap). Unmeasured ions are osmotically active substances that aren't measured ions, e.g. they could be sugar, fibre etc
A normal osmotic gap is 50-100 mOsm/kg.
High osmotic gap suggests osmotic diarrhoea.
Low osmotic gap suggests secretory diarrhoea.</p>
<p>Osmotic gap equation?</p>
<p>Stool osmotic gap = stool osmolality - (stool [Na+K] x 2)</p>
<p>Patient has bloody diarrhoea with abdominal pain, diagnosis?</p>
<p>Dysentery</p>
<p>What is dysentery?</p>
Low volume bloody diarrhoea:
<p>Inflammation/damage and/or disordered structure and function of intestine mucosa by:
* Direct invasion or
* Cytokine release</p>
<p>Which part of the intestine is most affected by dysentery?</p>
<p>Colon</p>
<p>What is the common length of time of dysentery?</p>
<p>2-7 days, and it's usually self-limiting.</p>
<p>What is the normal symptom development for dysentery?</p>
<p>Watery diarrhoea, then bloody diarrhoea +/- fever, malaise, other systemic sx</p>
<p>What are the common causal pathogens of dysentery?</p>
<p>CCHESS
~~~
C diff
Campylobacter
Haemorrhagic E-coli 0157
Entamoeba histolitica
Salmonella
Shigella</p>
~~~
<p>Severe diarrhoea in infant in winter in UK?</p>
<p>Rotavirus</p>
<p>Severe diarrhoea in nursary/school infant?</p>
<p>Rotavirus</p>
<p>What are the antigenic groups of rotavirus and which is the most important?</p>
<p>Groups A-G; A is most important</p>
<p>What is the most common mode of transmission of rotavirus?</p>
<p>Fomites (toys, hard surfaces) - spread within families / institutions</p>
<p>Leading cause of gastroenteritis worldwide?</p>
<p>Rotavirus</p>
<p>How long is rotavirus shed in stools for? (how long does a person remain infectious in that way?)</p>
<p>21 days</p>
<p>Outbreak of acute diarrhoea, not necessarily in children... likely cause?</p>
<p>Norovirus</p>
<p>Outbreak of acute diarrhoea in winter months in adults?</p>
<p>Norovirus</p>
<p>Outbreak of acute diarrhoea in adults in restaurant, hospital etc?</p>
<p>Norovirus</p>
<p>Acute diarrhoea after eating chicken?</p>
<p>Campylobacter (or salmonella)</p>
<p>Acute diarrhoea after drinking dairy/eggs/beef/fish?</p>
<p>Salmonella
(dairy could also be staph aureus)</p>
<p>Acute diarrhoea with development of haemolytic-uraemic syndrome (HUS)?</p>
<p>EHEC (E coli O157:H7 is one type of EHEC) </p>
<p>Acute diarrhoea following undercooked meat?</p>
<p>EHEC</p>
<p>Acute bout of traveller's diarrhoea?</p>
<p>ETEC
| </p>
<p>Rice water diarrhoea?</p>
<p>Vibrio cholera</p>
Raw or undercooked shellfish, particularly raw oysters?
Vibrio spp. Vibrio vulnificus, Vibrio parahaemolyticus
Acute diarrhoea from warm coastal area +/- seafood?
Vibrio
Severe dysentery in child under 5?
Shigellosis
Previous antibiotic use?
C Diff
Above 65 in hospital?
C Diff
What other non-antibiotic drugs raise chance of getting C diff and why?
PPIs through comprimised gastric acid barrier
Most common cause of parasitic acute diarrhoea in developed countries?
Giardia lamblia
Foul smelling flatulence, fatty stools +/- weight loss +/- recent travel?
Giardia
Persistent diarrhoea +/- weight loss after travel?
Giardia (also probably fatty/foul smelling may be mentioned)
Greatest cause of mortality to patients with HIV?
Diarrhoea! (why else would I put it in this stack?)
Common parasitic cause(s) of diarrhoea in HIV / immunocomprimised?
Cryptosporidium parvum Microsporidium Entamoeba histolitica Isospora bella
Most common cause of severe chronic diarrhoea in HIV patients?
Cryptosporidium
Recent ingestion of rice?
Bacillus cereus
Recent ingestion of dairy e.g. coleslaw, yogurt etc?
Staph aureus
Recent ingestion of beef?
Clostridium perfringens
What is the pathogenic mechanism of Cholera?
Releases enterotoxins into bowel, promoting secretion of isotonic fluid into small bowel lumen. A-B toxin (5 B subunits and 2 A subunits). B subunits bind and 2 A subunits enter. A1 increases a.c. activity almost permanently, increasing cAMP and causing cAMP activated chloride channel CFTR to open more than normal. Causes signifiant Cl- secretion with Na+ following, and with that, paracellular H2O secretion via tight junctions. Can lead to all sorts of problems inclduing arryhmias and cramps due to loss of K+ and metabolic acidosis due to loss of HCO3- (REMEMBER, ISOTONIC FLUID... remember in the hypovolaemia lectures, the water loss is isotonic, which means the ISF doesnt know about it and doesnt correct the loss)
Why do antibiotics predispose to C diff?
Disruption of commensal flora
C diff pathogenic mechanism?
Disturbance of small bowel / large bowel intestinal flora --> C diff colonisation --> two toxins produced: Toxin A - enterotoxin - activates CFTR = watery Toxin B - cytotoxin = blood diarrhoea
Diarrhoea following ingestion of milk products, following recent illness?
Induced lactase deficiency - when intestine becomes inflamed following a recent illness, the lactase brush-border enzyme can be lost, meaning that you lose the ability to digest lactase temporarily.
Four species of shigella?
Sonnei, flexneri, boydii, dysenteriae
Pathogenic mechanism of shigella?
Invades cell and multiplies inside cell Forms finger-like projections to neighbouring cells, pinching off in neighbouring cell membranes Cells are killed and abcessed can form, and local inflammation can occur Production of enterotoxin from some species, enhancing virulence as it causes capillary thrombosis --> haemorrhagic colitis
High fever (up to 40) --> rash on abdomen / chest, flu like symptoms --> diarrhoea. 1-2 weeks later develops delirium and severe exhaustion. Cause?
Salmonella typhi (typhoid)
Long duration of diarrhoea (3-10 weeks) + recent travel
Giardia
Drinking unfiltered water while travelling + long period of diarrhoea e.g. several weeks
Cryptosporidium
Tired all the time, diarrhoea, abdominal pain, constipation perhaps, flatulence? (Think food...)
Coeliac
Episodic flare ups of diarrhoea / constipation, OTHERWISE WELL. Also, how do you treat?
IBS (which is a multi-factorial disorder probably partly due to malabsorption, partly neuronal etc) Treat with reassurance, anti-spasmodics, anti-diarrhoeals if requested.
How to treat giardiasis?
Tinidazole or metronidazole
ETEC pathogenesis?
Attaches to mucosa and produces toxins which cause salt + water secretion.
Treatment for C diff?
Metronidazole, if fails, higher dose of metronidazole, if still fails, vancomycin.
General management plan for someone coming in with diarrhoea?
ABCDE + assess hydration status Aim to rehydrate
What is the best method of rehydration?
Enteral (oral/NGT). Parenteral only if: * suspected or confirmed shock * deterioration despite ORS * persistent vomiting of ORS * other obvious reasons e.g. not taking water
How to treat shock?
Oxygen Establish IV/IO access Initial STAT infusion of 20mL/kg of isotonic solution e.g. Hartmanns or 0.9% NaCl Monitor clinical response and listen to chest Repeat IV administration until clinical improvement. Consider causes of shock e.g. sepsis, and aim to treat.
Is 20mL/kg of IV infusion always appropriate for initial STAT therapy for shock?
No e.g. children, cardiac failure May cause pulmonary oedema
Appropriate IV fluids?
Ringers(Hartmann's) 0.9% NaCl (Normal saline)
What are the signs of overhydration?
Tachycardia Respiratory distress/cough Crackles in lung fieals Hepatomegaly Oedema (peri-orbital swelling)
```If patient is dehydrated + has jittery movements, increased muscle tone, hyperreflexia +/- convulsions/drowsiness/coma, what is possible cause and how do you treat?
Hypernatraemic dehydration (Serum Na+ >150mmol/L) Treat as above plus replac fluid more slowly (over 48 instead of 24h) and reduce serum Na+ slowly (
Clinical shock signs?
Decreased conciousness Pale/mottled skin Cold extremeties Weak pulses Prolonged CRT Hypotension ``` (+ the usual ones for dehydration e.g. tachycardia, tachypnoea, but they aren't shock specific)
What is maintenance dose of water and electrolytes after initial resuscitation?
20-30mL/kg/day water (1.5-2L) 1mg/kg/day of salts
Muscle wasting and little subcutaneous fat, inflammation in corners of mouth, conjunctival pallor... likely diagnosis? How does this affect acute diarrhoea treatment?
Severe Acute Malnutrition (SAM) seen as muscle wasting, reduced fat, angular stomatitis, conjuctival pallor Clinical signs of shock and dehydration are unreliable because Na+/K+ pump fails in SAM as not enough energy for ATP and so body loses a lot of K+ and gains a lot of Na+. Oral fluids are preferred as parenteral fluids can cause severe deterioration and IVF must be used cautiously... a lowr Na+ concentration e.g. 0.45% saline instead of 0.9%
