Nutrition: Basic Science Lecture Series

transcript

Nutrition

Basic Science Lecture Series

Umut Sarpel

8/11/05

Overview

• Calorie / protein requirements

• Respiratory Quotient

• Effects of starvation

• Benefits / risks TPN

• Enteral feeding

• Vitamin deficiencies

• Crohn’s disease

• Issues in bariatric surgery

Overview

• Enteral feeding

Calorie requirements

• Resting 70 kg male: 1450 kcal/day

• Post-operative: 1700 kcal/day

• Sepsis, head trauma, pancreatitis:

2400 kcal/day

• Burns (depends on size): 3000 kcal/day

Protein requirements

• In healthy adults:

0.8 gm / kg (56 gm / day for 70 kg patient)

• In stressed patients:

1.2-1.5 gm / kg

Overview

• Enteral feeding

Respiratory Quotient

• RQ = O2 consumption / CO2 production

• Carbohydrates ~ 1.0

• Protein ~ 0.81

• Lipids ~ 0.7

• Alcohol ~0.66

• Normal “American” diet RQ = 0.87

• Excess glucose leads to a RQ > 1.0

A patient s/p Whipple complicated by a leak with prolonged sepsis is now stable. She has failed 2 extubation attempts. Her RQ is likely

a) 0.66

b) 0.7

c) 0.8

d) 0.9

e) 1.1

A patient s/p Whipple complicated by a leak with prolonged sepsis is now stable. She has failed 2 extubation attempts. Her RQ is likely

a) 0.66

b) 0.7

c) 0.8

d) 0.9

e) 1.1

Respiratory Quotient

• An RQ > 1 indicates net lipogenesis

• Overfeeding syndrome is a common reason for failed extubation

• The excess glucose, converted to CO2, increases minute ventilation in order to prevent respiratory acidosis

• Re-evaluate caloric needs

Overview

• Enteral feeding

Starvation

• Glycogen from liver depleted in ~48 hrs

• The body first catabolizes skeletal muscle amino acids into glucose

• Certain tissues are highly dependent on glucose for energy, thus some glucose production is always required

• In prolonged starvation, the body will adjust to using fat stores, and proteolysis decreases

Starvation

• “The metabolic tragedy of sepsis”

• The normal suppression of proteolysis seen w/ prolonged fasting does not occur in sepsis

• Breakdown of protein continues

• Also, high cortisol levels lead to persistent hyperglycemia which inhibits lipolysis

• Thus septic pts can have enormous untapped fat stores and still catabolize muscle

The primary source for glucose in early starvation (1week) comes from

a) Proteins in skeletal muscle

b) Ketone bodies

c) Free fatty acids

d) Glycogenolysis

e) Lipolysis / Acetyl CoA

The primary source for glucose in early starvation (1week) comes from

a) Proteins in skeletal muscle

b) Ketone bodies

c) Free fatty acids

d) Glycogenolysis

e) Lipolysis / Acetyl CoA

Glucose is the primary fuel source for all the following tissues except

a) Renal medulla

b) Brain tissue

c) WBCs

d) RBCs

e) Peripheral nerves

f) Heart

Glucose is the primary fuel source for all the following tissues except

a) Renal medulla

b) Brain tissue

c) WBCs

d) RBCs

e) Peripheral nerves

f) Heart

Overview

• Enteral feeding

• Pre-operative albumin is a predictor of morbidity and mortality

• In mildly malnourished patients, pre-op TPN increased infectious complications

• In severely malnourished patients, TPN decreased non-infectious complications

• Refeeding syndrome (aka Phosphate steal): new glucose administration leads to rapid intracellular shifts of K, Phos, Mg, because they are used in glucose metabolism. Sudden drop in plasma levels seen.

• Especially, phosphate depletion leads to muscle weakness, respiratory distress

What is the maximum rate of glucose administration in TPN?

a) 1 gm/kg/hr

b) 5 gm/kg/hr

c) 10 gm/kg/hr

d) 15 gm/kg/hr

What is the maximum rate of glucose administration in TPN?

a) 1 gm/kg/hrb) 5 gm/kg/hrc) 10 gm/kg/hrd) 15 gm/kg/hr

Besides hyperglycemia, higher rates of glucose infusion can also cause vessel thrombosis

Overview

• Enteral feeding

Enteral feeding

• Nutrients are absorbed into portal system and pass through the liver (vs TPN)

• This allows for hepatic and intestinal production of products that have a role in anabolic signaling, leading to more efficient use of nutrients

• Full strength tube feeds may cause an osmotic diarrhea

• Always check residuals (<150cc)

Enteral feeding

• Immunonutrition: enteral diets enhanced with omega-3-fatty acids, RNA, vitamins, arginine, have been shown to reduce infectious complications in patients undergoing surgery for malignancy

Enteral feeding:

a) Prevents atrophy of intestinal villi

b) Prevents translocation of intestinal bacteria

c) Prevents immunoglobulin A deficiency

d) Usually causes diarrhea

Enteral feeding:

a) Prevents atrophy of intestinal villi

b) Prevents translocation of intestinal bacteria

c) Prevents immunoglobulin A deficiency

d) Usually causes diarrhea

Overview

• Enteral feeding

Vitamin deficiencies

• Vit A - poor healing, skin keratosis, night blindness• Vit D - osteomalacia• Vit E - dystrophic changes of retina• Vit K – coagulopathy• Thiamine – (beri beri) lactic acidosis, altered mental

status, DI, hyperbilirubinemia, thrombocytopenia

• Zinc - poor wound healing, impaired immunity• Biotin - alopecia, neuritis, dermatitis• Selenium - cardiomyopathy, hair loss, weakness• Essential fatty acids - scaly dermatitis

Causes of macrocytic anemia

• Dietary deficiency of B12

• Pernicious anemia (autoimmune destruction of gastric mucosa leading to a deficiency of intrinsic factor, which binds B12)

• Resection / bypass of stomach

• Resection / bypass of ileum

• Blind loop syndrome (bacterial overgrowth leads top competition for B12)

Overview

• Enteral feeding

Crohn’s disease

• Diseased terminal ileum

• Poor uptake of vitamins A, D, E, K

• Vit D deficiency, when combined with frequent steroid use may lead to osteoporosis

• Important to avoid multiple SB resections to prevent short gut. Strictuoplasty when possible.

What is the etiology of nephrolithiasis in patients with Crohn’s disease?

a) Hypercalcemia

b) Hyperuricosuria

c) Hyperoxaluria

d) Vitamin D deficiency

e) Dehydration

What is the etiology of nephrolithiasis in patients with Crohn’s disease?

a) Hypercalcemia

b) Hyperuricosuria

c) Hyperoxaluria

d) Vitamin D deficiency

e) Dehydration

Oxalate stones

• Oxalate is normally bound by calcium

• However, due to a diseased TI, bile salts and thus lipids are not well absorbed. The intralumenal calcium binds with fat (saponification) instead of oxalate. Oxalate is then absorbed in the colon, leading to hyperoxaluria and stone formation when excreted from kidney

What is the minimal length of SB needed to avoid short-gut syndrome?

a) ~40 cm of any portion of small bowel

b) ~60cm with ileo-cecal valve

c) ~120cm with ileo-cecal valve

d) ~120cm without ileo-cecal valve

What is the minimal length of SB needed to avoid short-gut syndrome?

a) ~40 cm of any portion of small bowel

b) ~60cm with ileo-cecal valve

c) ~120cm with ileo-cecal valve

d) ~120cm without ileo-cecal valve

Overview

• Enteral feeding

Bariatric surgery: deficiencies

• Iron and calcium deficiency (both absorbed in duodenum)

• B12 deficiency (lack of IF from bypassed stomach)

• A, D, E, K deficiencies

• Thiamine deficiency (likely from prolonged emesis) - can cause Wernicke’s

EXTRA-CREDIT

Some ABSITE favorites…

The principle fuel for colonocytes is

a) Butyrate

b) Acetoacetate

c) D-Glucose

d) Glutamine

e) Propionate

The principle fuel for colonocytes is

a) Butyrate

b) Acetoacetate

c) D-Glucose

d) Glutamine

e) Propionate

Principle fuel for colonocytes

• Butyrate is the major short-chain fatty acid

• The colon relies on bacterial fermentation for production of SCFA’s

• Colonic inflammation is seen in diversion colitis secondary to SCFA deficiency

• UC patients may have a relative SCFA deficiency, can treat w/ SCFA enemas

Branched-chain amino acids are

a) Useful in ESRD

b) Useful in ESLD

c) Useful in pts with COPD

Branched-chain amino acids are

a) Useful in ESRD

b) Useful in ESLD

c) Useful in pts with COPD

Branched-chain amino acids

• Leucine, isoleucine, valine

• Only amino acids that do not require metabolization by liver

• They can also be oxidized by muscle

• May be used for patients with liver failure

Glutamine is

a) Primary fuel for small bowel

b) Primary fuel for malignant cells

c) Most abundant free amino acid in the body

d) Synthesized by skeletal muscle

e) A conditionally essential amino acid

Glutamine is

a) Primary fuel for small bowel

b) Primary fuel for malignant cells

c) Most abundant free amino acid in the body

d) Synthesized by skeletal muscle

e) A conditionally essential amino acid

Nutrition: Basic Science Lecture Series

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