Diarrhoea And Fluid Replacement Therpay Flashcards

1
Q

Which electrolytes are most commonly absorbed in the small intestine?

A

Sodium and chloride

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2
Q

Which electrolytes are most commonly REabsorbed in the large intestine?

A

Bicarbonate
Potassium
Chloride

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3
Q

How does sodium enter the blood (concentration gradient )

A

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

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4
Q

What membrane transporters can sodium use to enter the intestinal cells?

A

Sodium symporter - can co-transport vitamins, amino acids, peptides, bile salts and glucose

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5
Q

How much water does an average persons take in and excrete in one day?

A

2000mls taken in

  • 100mls excreted as urine/faeces
  • 9000mls is turned over - this is where there is capacity for fluid loss
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6
Q

How does water get absorbed from the small intestine into the blood?

A

Paracellularly, following the sodium/concentration gradient

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7
Q

What is the function of glucose during absorption of sodium?

A

Glucose aids the absorption of sodium into the cell, so helps establish the concentration gradient

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8
Q

What are oral-rehydration salts

A

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

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9
Q

What is the name of the glucose/sodium symporter in the small intestine (apical membrane)

A

SGLUT-1 transporter

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10
Q

What’s is the name of the glucose transporter found on the basolateral membrane of the small intestine cell?

A

GLUT-2 transporter

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11
Q

On a basic level, what does the cholera toxins do to cause diarrhoea?

A

Counteract the electrolyte uptake in the intestines

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12
Q

What do the enterotoxins released by the cholera do?

A

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

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13
Q

What must the water content of stool be before it’s considered diarrhoea?

A

Greater than 200mls

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14
Q

What are the three types of diarrhoea?

A

Osmotic (malabsorptive)
Secretory
Inflammatory

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15
Q

What is the pathophysiology of osmotic diarrhoea?

A

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

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16
Q

Where is most water and electrolytes absorbed?

A

The small intestine

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16
Q

Give examples of non-absorbable, osmotically active solutes that can cause osmotic diarrhoea?

A

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

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18
Q

What is osmotic diarrhoea caused by?

A
Laxatives
Antacids
Orlistat (a lipase inhibitor)
Deficiency of digestive enzymes (pancreatic insufficiency)
Short bowel syndrome
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18
Q

How can osmotic diarrhoea be resolved?

A

Fasting

Patient stops eating the non-absorbable substance

19
Q

What is the pathophysiology of secretory diarrhoea

A

This is due to an increase in secretion or decrease in absorption of bicarbonate, sodium, potassium and chloride.
Net secretion exceeds net absorption

20
Q

What are some of the causes of secretory diarrhoea?

A
Acute infections - vibrio cholera 
Fat malabsorption
Failure of bile salt absorption
Laxative abuse
Some bacteria can even destroy the GAP junctions of cells of the bowel, causing water leakage
21
Q

What is the pathophysiology of inflammatory diarrhoea?

A

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

22
Q

What can cause inflammatory diarrhoea?

A

Chrons disease or ulcerative colitis
Bacterial: Salmonella or E.coli
Viral: rotavirus or Norovirus
Protozoal: giardia or cryptosporidium

23
Q

What are the most common causes of diarrhoea in children worldwide?

A

Acute watery diarrhoea - due to dehydration

  • v.cholera, e.coli, rotavirus
    Bloody diarrhoea - intestinal damage and nutrition loss
  • shigella
24
Q

How is diarrhoea in children treated?

A

Fluid replacement to prevent dehydration (oral rehydration salts)
Zinc supplements to reduce severity and duration of diarrhoea
Feeding - to provide nutrients

25
Q

What are most of the worldwide deaths from diarrhoea attributed to?

A

Poor sanitisation, unsafe water and poor hygiene

26
Q

What can be done to reduce deaths from diarrhoea?

A
Rotavirus/measles vaccination
Early breastfeeding and vitamin A supplements 
Community wide sanitation programme
Hand washing and soap
Better water quality
27
Q

What does the speed at which fluid should be replaced in someone with diarrhoea depend on?

A

Age
Renal function
Cardiovascular status

28
Q

What are the stages involved in assessing how much fluid to replace in someone with diarrhoea?

A
Assess the clinical status
Asses intake and output
Address any electrolyte shifts
Replace the fluid
- daily need
- anticipated losses
- previous deficit
29
Q

What are the two types of IV fluid you should give a person with severe water loss (after ORS)

A

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

30
Q

What is the function of colloids?

A

They quickly increase the intravascular volume because they stay 100% in the blood vessel

31
Q

How much of any given saline solution stays within the vascular wall?

A

25%, the rest is spread between the interstitium and inside cells

32
Q

How much of any given dextrose solution stays within the vascular wall?

A

10% - glucose enters the cell, leaving the water in the blood. This water then diffuses into tissues for use

33
Q

When is a 5% dextrose solution required?

A

Because the dextrose is immediately metabolised to water and carbon dioxide, it’s used when only water replacement is required (no electrolyte loss)

34
Q

What is the standard crystalloid ratio during fluid replacement?

A

2 saline : 1 dextrose

35
Q

How would someone who needed fluid replacement and a treatment for acidosis be treated?

A

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.

36
Q

How fast would a person be infused with a 500ml bag of saline in an emergency situation?

A

Over the course of 2 hours

37
Q

What is the equation needed to work out how much water replacement is needed?

A

Fluid required = measured loss + insensible losses + previous day’s deficit

38
Q

How much time is needed for one bag to infuse in a standard rehydration regime?

A

6 hours

39
Q

Why don’t you just replace fluid in an individual as quickly as possible?

A

Because there is a risk of overwhelming the cardiovascular system with too much fluid

40
Q

In which body compartment does the potassium concentration have to be tightly maintained?

A

The intravascular compartment - must be between 3.5-5mmol/l

41
Q

What happens when the potassium concentration is too high or too low?

A

Cardiac arrhythmias

Also causes more of a problem in renal patients

42
Q

How is potassium administered?

A

IV - stating the final volume of potassium required over a certain amount of time
- e.g. 20mmol/l in saline over 8 hours

43
Q

What’s the maximum concentration and rate that potassium can be delivered peripherally?

A

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

44
Q

At what potassium plasma level would you have baseline ECG monitoring, and at what level would you have cardiac monitoring?

A

A baseline ECG is needed if potassium is less than 3mmol/l

Cardiac monitoring is required if potassium is less than 2.5mmol/l

45
Q

Why is potassium loss a problem in diarrhoea?

A

Because potassium is secreted in the large intestines and is dragged out faster by the decreased osmolality of the luminal contents.

46
Q

How much potassium needs to be given a day (minimum) if there’s no oral intake?

A

60-80mmol/day, because that is how much a normal person loses and needs to replace in the diet.