Diarrhoea And Fluid Replacement Therpay Flashcards
Which electrolytes are most commonly absorbed in the small intestine?
Sodium and chloride
Which electrolytes are most commonly REabsorbed in the large intestine?
Bicarbonate
Potassium
Chloride
How does sodium enter the blood (concentration gradient )
The sodium in the intestinal cell is actively pumped out via the sodium-potassium pump on the basolateral membrane
- this creates a concentration gradient in the cell
Sodium in the lumen is dragged into the cell up the concentration gradient
What membrane transporters can sodium use to enter the intestinal cells?
Sodium symporter - can co-transport vitamins, amino acids, peptides, bile salts and glucose
How much water does an average persons take in and excrete in one day?
2000mls taken in
- 100mls excreted as urine/faeces
- 9000mls is turned over - this is where there is capacity for fluid loss
How does water get absorbed from the small intestine into the blood?
Paracellularly, following the sodium/concentration gradient
What is the function of glucose during absorption of sodium?
Glucose aids the absorption of sodium into the cell, so helps establish the concentration gradient
What are oral-rehydration salts
These are a treatment for dehydration that utilises the glucose/sodium symporter to aid sodium uptake into the blood.
Isn’t a treatment of the cause of the diarrhoea
What is the name of the glucose/sodium symporter in the small intestine (apical membrane)
SGLUT-1 transporter
What’s is the name of the glucose transporter found on the basolateral membrane of the small intestine cell?
GLUT-2 transporter
On a basic level, what does the cholera toxins do to cause diarrhoea?
Counteract the electrolyte uptake in the intestines
What do the enterotoxins released by the cholera do?
They activate the intracellular cAMP, activating protein kinase A and signalling CFTR
- cystic fibrosis transmembrane regulator
This removes chloride from the cell, back into the lumen, shifting the concentration gradient, and keeping the water in the intestines
What must the water content of stool be before it’s considered diarrhoea?
Greater than 200mls
What are the three types of diarrhoea?
Osmotic (malabsorptive)
Secretory
Inflammatory
What is the pathophysiology of osmotic diarrhoea?
Water-retention in the bowel due to an accumulation of non-absorptive water soluble substances
More fluid in the bowel, means the stool will travel faster and less water can be absorbed
Where is most water and electrolytes absorbed?
The small intestine
Give examples of non-absorbable, osmotically active solutes that can cause osmotic diarrhoea?
Carbohydrates
Magnesium sulphate
Lactose - due to lack of lactate
- once this passes into the colon, it’s fermented by the gut microflora to produce gas
What is osmotic diarrhoea caused by?
Laxatives Antacids Orlistat (a lipase inhibitor) Deficiency of digestive enzymes (pancreatic insufficiency) Short bowel syndrome