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
What is enteritis?
Inflammation of the small intestine
Where in the small intestine is Folate absorbed?
Proximal small intestine
Where in the small intestine is vitamin B12 absorbed?
Distal small intestine
What is absorbed in the proximal small intestine?
Fat Sugars Peptides and amino acids Iron Folate Calcium Water Electrolytes
What is absorbed in the distal small intestine?
Bile acids
Vitamin B12
Water
Electrolytes
What is absorbed in the middle small intestine?
Sugars Peptides and amino acids Calcium Water Electrolytes
Where in the small intestine is fat absorbed?
proximal small intestine
Where in the small intestine are sugars absorbed?
proximal and middle small intestine
Where in the small intestine are peptides and amino acids absorbed?
proximal and middle small intestine
Where in the small intestine is iron absorbed?
proximal small intestine
Where in the small intestine is calcium absorbed?
proximal and middle small intestine
Where in the small intestine is water absorbed?
the whole small intestine
Where in the small intestine are electrolytes absorbed?
the whole small intestine
Where in the small intestine are bile acids absorbed?
distal small intestine
What is short bowel syndrome?
a syndrome where you’ve got a section of the bowel that’s not working.
referring to having a base of the small intestine not being there
What causes short bowel syndrome?
Post operative Mesenteric ischaemia Crohn's disease Trauma Neoplasia Radiation enteritis
What part of the gut can you live without? What cant you live without?
Sections of the colon
Any part of the small intestine
What water/electroyte management is there? Mild to severe
Oral gluose/saline and Sodium chloride
Enteral- Ng tube
Parental going into vein
What are the inputs and outputs of the urea cycle?
Glutamine/ amino acid
NH3 through protein metabolism and carbamoyl phosphate
Urea -product
What is the urea cycle for?
Detoxify anomia into urea
If a patient has a defect in the Urea Cycle, what might happen if they are unable to eat?
Hyperammonaemia
What is MCADD short for?
Medium chain acyl-CoA dehydrogenase deficiency
What is MCADD?
Defect in fatty acid oxidation
What is the most common fatty acid oxidiation disorder
MCADD
What happens to people with MCADD in the fed state?
Nothing- because they are utilising glucose from carbohydrated and it is a fatty acid disorder
What happens to people with MCADD in the fasted state?
Hypoglycemia as fatty acids are utilised when starving
How does MCADD impact a baby?
Hypoglycemia therefore fatal for baby
When should we test for MCADD?
At birth
How is MCADD tested
Heel prick test
What criteria are there for an effective screening test/programme?
The condition should be an important health problem.
There should be an accepted treatment for patients with recognized
disease.
Facilities for diagnosis and treatment should be available.
There should be a recognizable latent or early symptomatic phase.
There should be a suitable test or examination.
The test should be acceptable to the population.
The natural history of the condition, including development from latent
to declared disease, should be adequately understood.
There should be an agreed policy on whom to treat as patients.
The cost of case-finding (including a diagnosis and treatment of
patients diagnosed) should be economically balanced in relation to
possible expenditure on medical care as a whole.
Case-finding should be a continuous process and not a “once and for
all proiect.
What is screened in the newborn screening programme
Sickle cell disease Cystic fibrosis Congenital hypothyroidism Phenylketonuria MCADD (Medium chain acyl-CoA dehydrogenase deficiency) Isovaleric acidaemia Glutaric aciduria type I Homocystinuria