Week 4 GI Lectures Flashcards
What happens if there is a large number of osmotically active molecules in the gut?
It starts to draw water at the cost of interstitial fluid which can lead to cellular dehydration
What does fluid accumulation in the gut cause?
Increased intestinal transit time which leads to a self propelling series of events that cause diarrhoea
What is osmotic diarrhoea?
When there are still solutes left in the lumen of the intestine which draw water into the lumen
What can cause osmotic diarrhoea?
- Laxatives, antacids,
- Acarbose(alpha-glucosidase inhibitor)
- Orlistat (lipase inhibitor)
- Digestive enzyme deficiencies (lactase)
- Pancreatic insufficiency
- Inflammatory disease
- Short bowel syndrome
What type of patient is more prone to electrolyte imbalances?
People who have had colon problems/ colon removed
What are the different types of ion transporter?
ATP driven pump
Co-transporter - symporter
Exchange carrier - antiporter
Ion channel
What drives the absorption of water in the intestine?
Sodium
What provides energy for the active transport of minerals, vitamins and metabolites in the intestine?
The sodium gradient
What happens if you introduce less osmotically active molecules to the gut?
There is less fluid movement
What is ORS?
Oral Rehydration Solution
What is secretory diarrhoea?
Endotoxins stimulate colonic electrolyte secretion which causes fluid to be drawn into the intestine
What is inflammatory diarrhoea?
The intestinal wall is damaged so causes diarrhoea as it cannot perform its function properly
What causes inflammatory diarrhoea?
Inflammatory bowel disease
Infectious disease
Irritable colon
How much potassium is outside the cells?
Only about 5%. The healthy potassium level must remain within a very specific limits.
What can high potassium levels cause?
Arrhythmias
What is key when undertaking FRT (fluid replacement therapy)?
Establishing a fluid balance chart – a record of intake and loss of fluid is important
Need to know if just dealing with loss of electrolytes and fluid or is it a shift between cells?
Once condition has been assessed need to think about replacing the fluids.
What are the different types of IV fluid replacement therapies?
- Colloids
- Crystalloids
What is the difference between colloids and crystalloids?
They stay in the vascular bed in different ways
How much of each fluid stays in the intravascular bed after infusion?
- colloids - initially nearly 100%
- saline - 25%
- dextrose - 10%
When would colloids be used?
When someone is bleeding a lot and you are trying to fill in the vascular bed (after acute haemorrhage)
When would saline be used?
If a patient is dehydrated but has not suffered an acute shock/haemorrhage
Saline has a higher retention than other crystalloids
When is dextrose used?
Good for giving water (cant give water directly IV).
Dextrose enters cells very quickly so leaves a lot of water behind
What are examples of isosmotic fluids?
- Saline (0.9%)
- Dextrose (5%)
- Sodium bicarbonate (1.96%)
What are examples of hyperosmotic fluids?
Sodium bicarbonate 8.4% is extremely hyperosmotic
What is an example of a hypoosmotic fluid?
Saline 0.45%
What happens if there are more osmotically active molecules in the cells than in the hypoosmotic plasma?
causes cells to draw in more water and can cause them to swell
What is the standard postoperative regimen?
Saline and dextrose (2:1) (two bags of saline to one bag of dextrose)
When are lactate containing fluids used?
In people with chronic acidosis.
A substantial amount of bicarbonate is produced during lactate metabolism: Thus Ringer-lactate solution may be used in metabolic acidosis caused by bicarbonate loss
what are examples of lactate containing IV fluids?
Ringer-lactate
Hartmann’s
How is IV potassium prescribed?
in mmol, indicating final volume of the solution: e.g. “20 mmol/L in saline, over 8h”
What is the maximum concentration for peripheral administration of potassium?
40mmol/l
What is the general rate and amount of fluid used for emergency re-hydration?
2-hourly 500ml bags
6L over 24hours
What is the general rate and amount of fluid used for a standard regimen?
6-hourly 500ml bags
2L over 24hrs
What is the general rate and amount of fluid used for slow rehydration?
8-hourly 500ml bags
1.5l over 24hrs
What factors should be taken into account when using fluid therapy?
- Age
- CV status
- Renal function
- Severity of dehydration
- How long it took for dehydration to develop
