Biochemical aspects of nutrition and metabolism Flashcards
What happens during starvation
First use more glucose than Beta- hydroxybutyrate
As you starve start using Beta- hydroxybutyrate+ acetoacetate.
After a few days start using glucose les than Beta- hydroxybutyrate so it is predominately used
No glucose= no insulin
Carbohydrate based -> fat based
Metabolic rate decreases
Start digesting muscles as a source of protein
Nutritional support to treat food not accessing the intestines (From not serious to severe)
Oral feeding - Supplements and dietary adjustments
Ng Tube - enteral
Gastronomy- More invasive
What happens if there is a problem with absorption ?
Total Parenteral nutrition TPN
Delivered into a large vein ( central vein ideally - peripheral vein if not normally antecubital fossa) and the portal system
What is the composition of total parenteral nutrition TPN?
Nitrogen Sodium Potassium Calcium Magnesium Phosphate
What happens if malnourished person is given food suddenly
Hyperglycemia (20% of TPN is dextrose)
therefore high insulin produced-> electrolytes shifted into cells
When would you use TPN?
When absorption into intestines is not working or when peristalsis isn’t working
How much calories is in TPN?
1800kcal
What is the normal source of glucose for the brain?
Gluconeogenesis
What is used for glucogenesis?
Glucose and amino acids
What is needed for ketone body formation?
Acetyl CoA
What is used to make Acetyl CoA to fuel the brain?
Metabolised fatty acids from adipose tissue
Which electrolyte will be driven into the cells by insulin? How?
Potassium by activating the sodium potassium pump
Magnesium
Phosphate
What which is used to treat breathlessness also drives potassium into cells
Salbutamol
Which electrolyte will be driven into the cells by salbutamol? How?
Potassium by activating the sodium potassium pump
What is the refeeding syndrome
Introduction of carbohydrates causes
- Increased insulin secretion
- Increase in thiamine utilisation
- Increased metabolic rate
Increased insulin secretion causes
-Drives potassium, phosphate and magnesium into cell
Reduction in these metabolites intravascularly
Increased metabolic rate causes
-increased strain on cardiovascular and respiratory systems
What you need to do when you start feeding someone
- Check K, Ca, PO4, Mg and all other urea and electrolytes
- Proactively prophylactically give vitamin supplementation such as thymine and B12.
- Start feeding slowly (0.418MJ/kg/day)
- Increase over 4-7 days
- Rehydrate carefully
- Supplement K, PO4, Ca and Mg
- Monitor bloods carefully
What needs to be at a normal level to make potassium and calcium levels up
Magnesium
What is intestinal failure?
Reduction in the function of the gut below the minimum necessary for the absorption of macronutrients and/or water and electrolytes such that IV nutrition is required
What are the types of intestinal failure?
- Type 1:Acute onset, usually self-limiting -most often seen after abdominal surgery
- Type 2:Less common — acute onset, usually following catastrophic effect (e.g. intestinal ischaemia)
- Type 3: Chronic — patients are metabolically stable but IV support is required over months — years. May or may not he reversible
What is intestinal ischaemia
Stroke of the gut
Clot or embolism cutting of blood supply in a portion of the bowel
What can happen if you have an abdominal surgery?
Post operative ileus
What is post operative ileus?
Bowel ‘doesn’t like it’ and hides
Therefore peristalsis stops and gut stops functioning so extra nutrition is needed
What types of intestinal failure are self-limiting?
1 and 2
What are the causes of intestinal failure?
Acute :
-Fistula/obstruction
-Small bowel dysfunction:
->Ileus
->Enteritis caused by:
--Chemotherapy
--Infection
Chronic
-Gut bypass
-Short bowel caused by:
->Jejunum-colon
->Jejunostomy
-Small bowel dysfunction
->Dysmotility
->Enteritis caused by:
--Irradiation
--Crohn's disease
