Nutrition Flashcards
What is the caloric requirement for an average healthy adult male (70kg)?
25 kcalories/kg/day
1500-1700 calories/day
What is the protein requirement for an average healthy adult male (70kg)?
1 g/kg/day
How many calories does fat provide per gram?
9 calories/g
How many calories does protein provide per gram?
4 calories/g
How many calories do carbohydrates provide per gram?
4 calories/g
How many calories does dextrose provide per gram?
3.4 calories/g
What percentage of calories should come from protein for an average healthy adult male?
20% of calories, with 20% being essential amino acids
What percentage of calories should come from fat for an average healthy adult male?
30% of calories
What percentage of calories should come from carbohydrates for an average healthy adult male?
50% of calories
How does trauma, sepsis, or stress affect caloric requirements?
Increases kcal requirement by 20-40%; 30 calories/kg/day; protein 1.5-2 g/kg/day
How much does pregnancy increase caloric requirements?
300 kcal/day
How much does lactation increase caloric requirements?
500 kcal/day
What is the protein requirement for obese patients?
2.5 g/kg/day with 20 calories/kg/day
hypocaloric high protein
How does the basal metabolic rate change with fever?
Increases by 10% for each degree above 38°C
Much of energy expenditure is used for heat production
What is the caloric requirement for burn patients with 2nd degree burns and at least 20% TBSA?
25 calories/kg/day + 30 kcal X percentage burned
What is the protein requirement for burn patients?
1.5-2 g/kg/day + 3 g/day X percent burned
What is the maximum caloric intake for burn patients?
Don’t exceed 3000 kcal/day
How is adjusted body weight calculated for caloric needs in overweight patients?
Adjusted body weight = (actual body weight - ideal body weight) X (0.25) + ideal body weight
What is the ideal body weight formula for men?
106 + 6 lb for every inch above 5 ft
What is the ideal body weight formula for women?
100 + 5 lb for every inch above 5 ft
What does the Harris-Benedict equation calculate?
Basal energy expenditure based on weight, height, age, and gender
What is the maximum glucose given in central line TPN?
3 g/kg/hour
What is PPN and its caloric composition?
Fat based, about 50% of calories from fat, use 5% dextrose in PPN
(TPN glucose based)
PPN: no evidence it improves outcomes; may impair immune responsiveness
What is the primary nutrient for colonocytes?
Short chain fatty acids
In patients with diversion (colostomy) they may get diversion colitis in rectal pouch; tx short chain fatty acid enema
Glutamine
Non-essential amino acid, can become conditionally essential in stressed states. Arginine too.
Most common AA in blood and tissue. 75% in mm. Also made in muscle
Necessary for nucleotide synthesis
Majority of fuel for enterocyte; also proliferating lymphocytes
Primary fuel for neoplastic cells
MC AA released from muscle in catabolism, alanine #2
Used in gluconeogenesis as an energy source
Enhances immune function by inhibiting small bowel mucosal breakdown and prevents translocation
Releases NH4 in kidney, so helps nitrogen excretion Urea cycle
Bone marrow transplant have decreased infection when supplemented with glutamine
What is the best indicator of pre-operative nutritional status?
Albumin
Low albumin < 3.0: strong risk factor for morbidity and mortality after surgery
What is the half-life of albumin?
21 days
What is the half-life of transferrin?
8 days
What is the half-life of prealbumin?
2 days
What is the normal protein level range?
6-8.5 g/dL
What is the albumin level range?
3.5-5.5 g/dL
What is the prealbumin level range?
15-35 mg/dL
What are acute indicators of nutritional status?
1 prealbumin, retinal binding protein, transferrin
Nitrogen balance
Nitrogen balance - 1 g of nitrogen contains 6.25 g of protein
Total protein for a health 70 kg male synthesized is 250g/day
N in – N out = N balances
(protein/6.25) – (24 hour urine nitrogen + 4) = Nitrogen balance
Positive = anabolism. Negative = Catabolism
In order to prevent negative nitrogen balance, 1 g of nitrogen should be provided for every 150 k/cal
Liver
- Responsible for AA production and breakdown
- Majority of protein breakdown from skeletal muscle is #1 glutamine, and alanine
- Urea production Is used to get rid of ammonia NH3, from AA breakdown
What is the primary NH3 donor in the urea cycle?
Glutamine
reaction occurs in the liver and urea is removed by the kidney; this accounts for 90% of nitrogen loss
What are essential fatty acids?
Essential fatty acids
- Linolenic (Omega 3), linoleic (omega 6)
- Unsaturated fatty acid
- Plays a role in cell membrane synthesis and inflammation.
- Needed for prostaglandin synthesis (long chain fatty acid).
Omega 3 - Linolenic
- Polyunsaturated fatty acids
- Humans do not synthesize unsaturated fatty acids
- Anti-inflammatory, anti-thrombotic, anti-atherosclerotic effects protect against heart disease
Omega 6 – linoleic
- Same as above but is proinflammatory
- Protects against heart disease
Carbohydrate metabolism
Glucose and galactose absorbed by secondary active transport (Na gradient by ATPase) and released into portal vein
Fructose - by facilitated diffusion and release into portal vein
Enterocyte can only absorb monosaccharides
Sucrose - fructose and glucose
Lactose - galactose and glucose
Maltose - glucose and glucose
Protein digestion
Begins with stomach pepsin, then trypsin, chymotrypsin, and carboxypeptidase
Broken down to AA, dipeptides, and tripeptides
Absorbed by secondary active transport; released as free AA into portal vein
AA are taken up by cells under influence of
AA are taken up by cells under influence of insulin
What happens to amino acids during stress?
Amino acids are shunted to the liver for gluconeogenesis.
Why should protein intake be limited in liver and kidney failure?
To avoid ammonia and urea build-up respectively, which can worsen encephalopathy.
What are branched chain amino acids?
They are essential amino acids: leucine, isoleucine, and valine (LIV). Metabolized in muscle and serve as a main source of energy for muscle protein.
What are the main deficiencies after gastrectomy?
Iron, vitamin B12, and calcium.
TPN
10% AA
25% dextrose
Electrolytes Na, Cl, Ca, Mg, PO4, acetate = buffer to increase pH (prevents metabolic acidosis)
Need 2 mg/kg/day of sodium
Need 1 mg/kg/day of potassium
10% lipid solution = 1.1 calories/cc. (so 500 cc of 10% lipids = 550 calories)
20% lipid solution = 2.0 calories/cc (so 500 cc of 20% lipid = 1000 calories)
TPN can cause calcium bilirubinate gallstones
Liver failure has a higher risk in children than adults
What deficiency can occur if minerals are not added to TPN?
Zinc deficiency= skin rashes and hair loss
What vitamin needs to be added separately in TPN?
Vitamin K.
When is post-operative TPN considered?
When enteral feeding is expected to be impossible for 7-10 days in well-nourished patients or 5-7 days in critically ill or malnourished patients.
When should pre-operative TPN be considered?
If enteral feeding is not possible and surgery is in 3-5 days, especially in severely malnourished patients.
What complication can TPN cause?
Calcium bilirubinate gallstones.
Who has a higher risk of liver failure due to TPN?
Children have a higher risk than adults.
What long-term effect can TPN have?
It can cause cirrhosis and various deficiencies.
What are the symptoms of zinc deficiency?
Eczematoid rash in perioral and intertriginous areas, hair loss, delayed wound healing, and thrombocytopenia.
What are the symptoms of essential fatty acid deficiency?
Dry scaly rash (KEY difference vs zinc) and hair loss, delayed wound healing, and thrombocytopenia.
What are the symptoms of copper deficiency?
Microcytic anemia, pancytopenia, neurological issues, ataxia, and diabetes.
Seen with TPN without trace mineral supplemntation and after gastric bypass
What are the symptoms of vitamin K deficiency?
Coagulopathy.
What are the symptoms of selenium deficiency?
Cardiomyopathy.
What deficiency is most common in TPN?
Zinc deficiency.
What are the symptoms of pyridoxine (B6) deficiency?
Peripheral neuropathy, glossitis, and sideroblastic anemia.
What are the symptoms of niacin deficiency?
Pellagra (diarrhea, dermatitis, dementia).
What are the symptoms of vitamin E deficiency?
Peripheral neuropathy, ataxia, and hemolytic anemia.
What are the symptoms of thiamine deficiency after bariatric surgery?
Wernicke’s syndrome (ataxia, confusion), peripheral neuropathy (dry beriberi), and congestive heart failure (wet beriberi).
What are the symptoms of folate deficiency?
Macrocytic anemia.
What are the symptoms of vitamin D deficiency?
Rickets.
What are the symptoms of vitamin C deficiency?
Scurvy.
What is immunonutrition?
Includes omega-3 fatty acids, glutamine, and arginine to lower infectious complications.
How do you calculate calories in TPN?
For a 1000cc bag of TPN with 20% dextrose, 7% protein, and 250 cc of 20% lipid:
- 0.2 X 1000 = 200 gm dextrose. 200 gm X 3.4 c/g = 640 calories.
- 1000 X 0.07 = 70 gm protein. 70 gm X 4 = 280 calories.
- 250 cc of 20% lipid = 50 gm fat (0.2 X 250 = 50 grams fat).
- 50 gm fat X 9 = 450 calories.
Post pyloric vs gastric feeding
Lower rates of pneumonia with post pyloric feedings
Increased total nutrition with post pyloric feeding
Patients with delayed gastric emptying, diabetes, GERD, should consider post pyloric feeding
Pre-op nutrition
Pre-op nutrition is only indicated for patients with severe malnutrition undergoing major abdominal or thoracic surgery
- Decreases overall complications and LOS
- No affect on mortality
Enteral feeding
increases survival with sepsis and pancreatitis
RQ respiratory quotient
Ratio of CO2 produced to O2 consumed - measures energy expenditure
RQ > 1 lipogenesis (overfeeding), tx: decrease calories and carbs.
Excess dextrose or overall energy can cause increase dependence to ventilator in those intubated; higher C02 production
RQ < 0.7 ketosis and fat oxidation (starving), pure fat utilization
Pure protein utilization 0.8
Pure carbs 1.0
Balanced nutrition 0.825
Postoperative phases
Catabolic phase – POD 0-3 (negative nitrogen balance)
Diuresis phase – POD 2-5
Anabolic phase – POD 3-6 (positive nitrogen balance)
Starvation or major stress
- Body uses glucose as main source of fuel in non-starvation state, then switches to glycogen (liver and muscle) then uses fat (fatty acids)
- Amino acids from protein break down can be used for gluconeogenesis in liver (early starvation) and kidney (late starvation)
- Lactate and Glycerol can be used by liver for gluconeogenesis
- Fatty acids can be used for most tissues except brain, because can’t cross BBB
- After 2-3 days THE LIVER starts making Ketones FROM Fatty acids. Brain uses Ketones as main source of energy
- After 6-8 days of fasting the body will get glucose supply from break down of MUSCLE protein into AA. These AA are converted to glucose by the liver in gluconeogenesis
Fat stored as adipose tissue is released into the blood stream as free fatty acids when glucose and insulin are low and glucagon and epinephrine are high
Protein conserving mechanisms do not occur after trauma or surgery (stressed state) 2/2 to catecholamines and cortisol
But does occur with starvation
Fat is the main source of energy in starvation
In trauma it is mixed with protein and fat
Must feed by 7 days of starvation
Feed gut to prevent translocation and TPN complications
Place PEG when predicted lack of feeding is > 4 weeks
During prolonged starvation; heart, skeletal muscle, kidney, and brain use ketones as main energy source
In extended fasting ketones become an important fuel source for brain after 2 days and gradually become principal fuel source
Late starvation - gluconeogenesis occurs in kidney
Heart, skeletal muscle, liver, Colonocyte prefer Fatty acids as main energy of fuel
Peripheral nerves, adrenal medulla, RBC, WBC, are obligate glucose users
Lipid breakdown stimulated by decrease in insulin and increase in glucagon
Tube feeds
- Diarrhea: slow rate, add fiber, make less concentrated feed
- High gastric residuals: Reglan, erythromycin
- Renal formulations: Less K, phosphate, and protein
Glycogen stores
Deplete after 24-36 hrs of starvation. ⅔ muscle and ⅓ liver, body then switched to fat
Glycogen from muscle is broken down to glucose-6-phosphate, but can’t go into blood stream b/c muscle doesn’t have g-6-phosphatase (only found in liver).
So G-6-P in muscle stays there and is utilized there
The liver is the main source of systemic glucose during stress or starvation in the first 24-36 hours
Gluconeogenesis
Hepatic glycogen depletes after 24h of fasting
Stimulated by glucagon
Gluconeogenesis precursors: Amino acids, especially alanine (primary substrate for gluconeogenesis), also glutamine, lactate, pyruvate, glycerol;
Occurs in the liver
Alanine and phenylalanine are the only AA to increase during stress
When liver uses all of alanine, kidney takes over for gluconeogenesis and uses glutamine
Low glucose signals a decrease in insulin release.
Glucagon, epi, and cortisol primarily promote gluconeogenesis and limit utilization of pyruvate as fuel to allow it for liver gluconeogenesis.
Alanine is the primary substrate for hepatic gluconeogenesis.
Skeletal muscle lactate (Cori Cycle) production alone, is insufficient to provide systemic glucose levels during fasting
Therefore, protein must be broken downAA. To sustain hepatic gluconeogenesis
Proteolysis results from decreased insulin and increased cortisol, primarily occurs in skeletal muscle, and causes increased urinary nitrogen excretion
There is less gluconeogenesis in starving states. High in stressed (surgery) state
Refeeding syndrome
- Alcohol abuse often present
- Shift from fat to carb metabolism
- Symptoms usually occur on day 4 following feed
- Low K, Mg, PO4
- Causes cardiac dysfunction, weakness, CHF, failure to wean vent, Respiratory failure, Encephalopathy
- Low ATP is most significant problem
- Prevent this by refeeding at a low rate, giving vitamin B, thiamine, and multivitamin before starting feeds
Cachexia
Cachexia mediated by TNF alpha
Kwashiorkor
ANASARCA. Normal-to-moderate calorei intake but inadequate protein intake.
Hypoalbuminemia, dependent edema
Enlarged fatty liver due to decreased carrier protein synthesis and decreased lipoprotein transport from the liver
(contrast to marasmus= insufficient intake of both calories and protein)
Marasmus
starvation from overall low calories
What are triacyl glycerides, cholesterol, and lipids broken down by?
They are broken down by pancreatic lipase and cholesterol esterase into micelles and free fatty acids.
What are micelles?
Micelles are aggregates of bile salts, long chain free fatty acids, cholesterol, and fat soluble vitamins.
- Cholesterol is used to synthesize bile salts
- Core has fat. Outer rim with bile acids and phospholipid
- Fat soluble vitamins absorbed in micelles
How do micelles and medium/short chain fatty acids enter intestinal cells?
They enter the intestinal cells, where TAGs are resynthesized and placed in chylomicrons.
- Chylomicrons - mainly 90% TAGS, enter lymphatics
- Short and medium chain fatty acid traverse enterocyte by simple diffusion. These enter the portal system, carried by albumin
How do long chain fatty acids enter enterocytes?
Long chain fatty acids form micelles with bile and enter the enterocyte by fusion with the membrane. They enter the lymphatics (terminal villous lacteal).
What happens to the remnant of chylomicrons after metabolizing triglycerides?
The remnant enters the liver, where cholesterol is synthesized and released within VLDL that contains triglycerides and cholesterol.
What is VLDL metabolized into?
VLDL is metabolized in the peripheral vascular endothelium into LDL, which transfers cholesterol from the liver to peripheral tissues.
LDL
- LDL will be deposited into body tissues or back to liver to help with cholesterol synthesis
What is the role of HDL?
HDL transfers cholesterol from tissue to liver.
What enters the portal system?
Medium and short chain fatty acids, amino acids, and carbohydrates enter the portal system.
What is the function of lipoprotein lipase?
on endothelium of liver and adipose tissue Clears chylomicrons and TAG from blood, breaking them down into fatty acids and glycerol which will be used as fuel in the liver, heart and skeletal muscle.
What does LDL do?
LDL – transfers hepatic cholesterol to peripheral tissues. Formed by metabolism of VLDL in the periphery by lipoprotein lipase. It is uptaken by the liver and peripheral tissues to help make cholesterol
What is the function of free fatty acid binding protein?
Free fatty acid binding protein - on endothelium of liver and adipose tissue; binds short and medium chain fatty acids
What are saturated and unsaturated fatty acids used for?
Saturated fatty acids are used for fuel by cardiac and skeletal muscles.
Unsaturated fatty acid - used for structural component of cells
What is the preferred energy source for colonocytes, liver, heart, and skeletal muscle?
Fatty acids, particularly ketones like acetoacetate and beta-hydroxybutyrate, are the preferred energy source.
- Fatty acid (ketones – acetoacetate, beta-hydroxybutyrate) – preferred energy source for colonocytes, liver, heart and skeletal muscle
What does hormone sensitive lipase do?
in fat cells, breaks down TAGs (storage form of fat) to fatty acids and glycerol into blood stream. (sensitive to GH, catacholemines, and glucocorticoids)
AA with increased release from skeletal muscle during hypermetabolic stress (burn, trauma, major surgery)
Glutamine: delivered to GI tract, where it serves as a nutrient to enterocytes and will be metabolized and deaminated. Ammonia resulting from deamination will be transferred to the liver via the portal vein and transformed to urea.
Alananine will be transferred to the liver for gluconeogenesis
Duke University Pre-Operative Nutrition Score
-Identify malnutrition and allow for intervention to decrease risk of perioperative complications
-BMI (<18.5; if older than 65, then <20)
-Weight loss in preceding 3 months
-Decrease appetite in prior week
-Automatic qualifiers for intervention: albumin < 3, vitamin D < 20
Indicators of significantly increased risk of malnutrition
-Weight loss of > 5% in 1 month or > 10% in 6 months
-BMI < 20 -21
-Significantly decreased oral intake
-Advanced age
-Critical illness
-Critically ill or suspected of malnutrition: nutritional screening w/n 24 hrs of being admitted
-Albumin not a marker for nutritional assessment- more closely related to inflammation in states of acute and chronic illness
Calculate nutritional requirement: 60-kg pregnant female
-Baseline energy expenditure in a normal weight person: 25 kcal/day
-Preganant: additional 300 kcal/day
=(25 x 60) + 300= 18000 kcal/day
Low chromium
Poor glycemic control
S/p AAA repair, abdominal distention, paracentesis shows clear fluid with triglyceride concentration of 205
-Chylous ascites 2/2 lymphoperitoneal fistula formation
-Low fat, hight protein diet with medium-chain fatty acid supplementation (not secreted into chylomicrons); can add octreotide to decrease lymphatic flow
=2nd line: bowel rest, TPN
