Flashcards in Diarrhoea And Fluid Replacement Therpay Deck (47):
Which electrolytes are most commonly absorbed in the small intestine?
Sodium and chloride
Which electrolytes are most commonly REabsorbed in the large intestine?
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)
What's is the name of the glucose transporter found on the basolateral membrane of the small intestine cell?
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?
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?
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?
Orlistat (a lipase inhibitor)
Deficiency of digestive enzymes (pancreatic insufficiency)
Short bowel syndrome
How can osmotic diarrhoea be resolved?
Patient stops eating the non-absorbable substance
What is the pathophysiology of secretory diarrhoea
This is due to an increase in secretion or decrease in absorption of bicarbonate, sodium, potassium and chloride.
Net secretion exceeds net absorption
What are some of the causes of secretory diarrhoea?
Acute infections - vibrio cholera
Failure of bile salt absorption
Some bacteria can even destroy the GAP junctions of cells of the bowel, causing water leakage
What is the pathophysiology of inflammatory diarrhoea?
A result of exudation of mucus, blood and protein from sites of active inflammation within the bowel
This increases osmotic load and water shifts into the lumen
Also, if a large surface area is damaged, intestinal absorption will be impaired
What can cause inflammatory diarrhoea?
Chrons disease or ulcerative colitis
Bacterial: Salmonella or E.coli
Viral: rotavirus or Norovirus
Protozoal: giardia or cryptosporidium
What are the most common causes of diarrhoea in children worldwide?
Acute watery diarrhoea - due to dehydration
- v.cholera, e.coli, rotavirus
Bloody diarrhoea - intestinal damage and nutrition loss
How is diarrhoea in children treated?
Fluid replacement to prevent dehydration (oral rehydration salts)
Zinc supplements to reduce severity and duration of diarrhoea
Feeding - to provide nutrients
What are most of the worldwide deaths from diarrhoea attributed to?
Poor sanitisation, unsafe water and poor hygiene
What can be done to reduce deaths from diarrhoea?
Early breastfeeding and vitamin A supplements
Community wide sanitation programme
Hand washing and soap
Better water quality
What does the speed at which fluid should be replaced in someone with diarrhoea depend on?
What are the stages involved in assessing how much fluid to replace in someone with diarrhoea?
Assess the clinical status
Asses intake and output
Address any electrolyte shifts
Replace the fluid
- daily need
- anticipated losses
- previous deficit
What are the two types of IV fluid you should give a person with severe water loss (after ORS)
Colloids have a large molecular weight and can include albumin, HES and haemaccel
Crystalloids are more common, containing water and electrolytes. Examples are saline, dextrose, ringer-lactate and Hartmann's
What is the function of colloids?
They quickly increase the intravascular volume because they stay 100% in the blood vessel
How much of any given saline solution stays within the vascular wall?
25%, the rest is spread between the interstitium and inside cells
How much of any given dextrose solution stays within the vascular wall?
10% - glucose enters the cell, leaving the water in the blood. This water then diffuses into tissues for use
When is a 5% dextrose solution required?
Because the dextrose is immediately metabolised to water and carbon dioxide, it's used when only water replacement is required (no electrolyte loss)
What is the standard crystalloid ratio during fluid replacement?
2 saline : 1 dextrose
How would someone who needed fluid replacement and a treatment for acidosis be treated?
They would receive dextrose, saline and one of either Hartmann's or ringer-lactate. These contain lactate which is metabolised within the body to bicarbonate.
How fast would a person be infused with a 500ml bag of saline in an emergency situation?
Over the course of 2 hours
What is the equation needed to work out how much water replacement is needed?
Fluid required = measured loss + insensible losses + previous day's deficit
How much time is needed for one bag to infuse in a standard rehydration regime?
Why don't you just replace fluid in an individual as quickly as possible?
Because there is a risk of overwhelming the cardiovascular system with too much fluid
In which body compartment does the potassium concentration have to be tightly maintained?
The intravascular compartment - must be between 3.5-5mmol/l
What happens when the potassium concentration is too high or too low?
Also causes more of a problem in renal patients
How is potassium administered?
IV - stating the final volume of potassium required over a certain amount of time
- e.g. 20mmol/l in saline over 8 hours
What's the maximum concentration and rate that potassium can be delivered peripherally?
40mmol/l is the maximum concentration that can be administered peripherally
The maximum rate is 10mmol/hr, unless there is cardiac monitoring or a central line, then it can be increased to 20mmol/hr
At what potassium plasma level would you have baseline ECG monitoring, and at what level would you have cardiac monitoring?
A baseline ECG is needed if potassium is less than 3mmol/l
Cardiac monitoring is required if potassium is less than 2.5mmol/l
Why is potassium loss a problem in diarrhoea?
Because potassium is secreted in the large intestines and is dragged out faster by the decreased osmolality of the luminal contents.