Nutrition provision Flashcards
Aims of artificial nutrition
to maintain/restore body composition with nutritionally rational and balanced intakes (research is looking at best way to maintain/restore/modulate cell and organ function with specific AAs, antioxidants, micronutrients and PUFAs -> immuno-nutrition to optimize outcome)
Energy requirements
in healthy subjects = food energy intake which balances total energy expenditure
Feeding objectives
minimalize losses (provide energy = provide energy => TEE)
Avoid
underfeeding (tissue energy mobilization development of malnutrition), overfeeding (excessive deposition/obesity and re-feeding syndrome -> metabolic complications of hyperalimentation)
Food energy
stored 5kcals/g weight gain (rehabilitation and growth), consumed -> releases heat & work (TEE), CO2 and urea
Maintenance energy requirements
= total energy expenditure -> calculate by adding BMR (prediction equations +/- 10% for weight/age/gender) +all other output (physical activity level/PAL and thermogenesis); TEE = BMR x PAL
BMR
while PAL value is low, this is increased due to diseased state (pyrexia increases 13%/degree increase in temperature, generalized hypermetabolism) -> fall in activity may be balanced by this increase (maintenance needs may be similar to or greater than normal subjects)
Energy needs of patients
healthy young adult male -> BMR is 24kcal/kg, PAL is 1.6 -> need 2660kcal/day -> TEE may vary between 1700-2500kcal (30-35kcal/kg/day)
Males
need 25-30kcal/kg/day of non-protein energy and 30-35kcal/kg/day of total energy
Females
need 20-25kcal/kg/day of non-protein energy and 25-30kcal/kg/day of total energy
Malnourished patient
aim for an additional 5kcal/kg expected weight gain
Food protein
used to replete tissues and replace nitrogen losses (maintenance of AA metabolism)
Nitrogen losses
surfaces (skin/hair growth, sweat and secretions), urine (urea, NH4, creatinine), feces ->
Healthy subject
protein losses vary with protein intake at average requirement intake (minimum intake for balance) -> 100mgN/kg = .63gprotein/kg/day
ICU patients
need protein >200mgN/kg = 1.3gprotein/kg/day
Protein needs
depends on metabolic status (catabolic state/normal metabolism) and nutritional status (depleted body composition or normal body composition)
Catabolic state, normal or depleted body composition
If you give them nothing they will be in negative nitrogen balance -> cannot replace all nitrogen losses until you fix catabolic state (excess protein comes straight out) -> curve rises to a plateau that is still in negative balance -> minimalize losses of LBM -> use up to 1.5g/kg (.25gN) to reduce negative balance
Normal metabolism, severe depletion
high protein feeds provide 1.9-2.2kg per day -> protein puts them in a significantly positive balance
Normal metabolism, normal body composition
maintain balance in normal patients -> RDA = .83 g/kg (.13gN)
Protein needs increase
with catabolism associated with SIRS and with tissue depletion in malnutrition -> aim to minimalize losses in catabolic patients and maintain balance in normal patients and replete losses in malnourished depleted patients
Normal feeds
1.3-1.5g/kg protein
High protein feeds
1.9-2.2g/kg protein
Carbohydrates
may have lactose intolerance, may have problems with osmolality/diarrhea -> use polysaccharides -> used to satisfy glucose requirements of tissues, to maintain moderate insulin levels
50% of energy needs!
How much carbohydrates are needed
CO2 production problem (limit use of carbohydrates)
better to use fat than carbohydrates because of this problem -> 42% more CO2 from carbohydrates than from fat -> potential for respiratory failure and/or respiratory acidosis
Lipids
minimum requirements are 3-5% as EFAs, maximum is all non-protein energy (may cause high plasma NEFA levels in catabolic patients -> need for restraint)
20-30% of non-protein calories!
How much lipids are needed
Types of lipids
medium chain TGs are best for ease of absorption and tissue consumption -> usually soybean oil = intralipid-> n-6 PUFAs (linoleic acid -> 52%), n-3 PUFAs (alpha-linoleic acid -> 7%) -> may be too much n-6 compared to n-3
N-6 fatty acid (linoleic acid -> 18:2)
produces arachidonic acid -> 2-series PG and 4 series LT -> inflammation and dysregulated immunity
N-3 fatty acids (alpha-linoleic acids -> 18:3)
produces EPA (DHA in fish oil) -> reduces production of arachidonic acid products; produces 3-series PG and 5 series LT -> less inflammation and improved immunity
Alternatives to soybean oil
MC TGs, olive oil (oleic acid -> MUFA -> reduce excessive n-6 FA), fish oil (reduce high n-6: n-3 ratios)
Nutritional implications for therapy
no quantitative data on requirements -> enteral feeds usually replete but TPN solutions may require supplementation prior to use -> cocktails of key vitamins are given enterally in many centers during severe catabolic stress
Vitamins and trace elements for IV nutrition
catabolic patients have increased requirements -> prior malnutrition (depleted levels), increased needs with increased metabolic rate (B vitamins -> thiamine, riboflavin and niacin), increased needs for antioxidants (vitamin C, E, selenium, B6, riboflavin)
B6
cofactor for cysteine/glutathione synthesis,
Riboflavin
cofactor for glutathione reductase
Trace elements (Fe, Cu, Mn, Zn)
100% utilization with IV route compared to with enteral route (no regulation of absorption so give much less -> 15-45% of usual)
Immuno-nutrition (post-surgery, critical illness, burns)
improved barrier function, improved immune function, decreased hyperinflammation, improved wound healing -> all lead to better clinical outcome -> this is a research area rather than established practice
Immunonutrients
AA (glutamine, arginine, cysteine), antioxidants, fish oils -> not always available at hospitals
Glutamine
especially parental route -> has benefit in both post-surgery and critically ill patients
Arginine
enteral feeds have benefit in post-surgery patients -> use in critically ill patients is controversial
Very-long chain n-3 PUFAs from fish oil
emerging as having a potentially beneficial immunomodulatory actions
