Caloric need – approximately 20–25 calories/kg/day

  Calories:

  Nutritional requirements for average healthy adult male

•  20% protein calories (1 g protein/kg/day; 20% should be essential amino acids)

•  30% fat calories – important for essential fatty acids

•  50% carbohydrate calories

  Trauma, surgery, or sepsis stress can increase kcal requirement 20%–40%

  Pregnancy increases kcal requirement 300 kcal/day

  Lactation increases kcal requirement 500 kcal/day

  Protein requirement also increases with above

  Burns

•  Calories: 25 kcal/kg/day + (30 kcal/day × % burn)

•  Protein: 1–1.5 g/kg/day + (3 g × % burn)

  Much of energy expenditure is used for heat production

  Fever increases basal metabolic rate (10% for each degree above 38.0°C)

  If overweight and trying to calculate caloric need, use equation: weight = [(actual weight − ideal body weight) × 0.25] + IBW

  Harris–Benedict equation calculates basal energy expenditure based on weight, height, age, and gender

  Central line TPN – glucose based; maximum glucose administration – 3 g/kg/h

  Peripheral line parenteral nutrition (PPN) – fat based

  Short-chain fatty acids (eg butyric acid) – fuel for colonocytes

  Glutamine – fuel for small bowel enterocytes

•  Most common amino acid in bloodstream and tissue

•  Releases NH₄ in kidney, thus helping with nitrogen excretion

•  Can be used for gluconeogenesis

  Primary fuel for most neoplastic cells – glutamine

PREOPERATIVE NUTRITIONAL ASSESSMENT

  Approximate half-lives

•  Albumin – 18 days

•  Transferrin – 10 days

•  Prealbumin – 2 days

  Normal protein level: 6.0–8.5

  Normal albumin level: 3.5–5.5

  Acute indicators of nutritional status – retinal binding protein, prealbumin, transferrin

  Ideal body weight (IBW)

•  Men = 106 lb + 6 lb for each inch over 5 ft

•  Women = 100 lb + 5 lb for each inch over 5 ft

  Preoperative signs of poor nutritional status

•  Acute weight loss > 10% in 6 months

•  Weight < 85% of IBW

•  Albumin < 3.0

  Low albumin (< 3.0) – strong risk factor for morbidity and mortality after surgery

RESPIRATORY QUOTIENT (RQ)

  Ratio of CO₂ produced to O₂ consumed – is a measurement of energy expenditure

  RQ > 1 = lipogenesis (overfeeding)

•  Tx: ↓ carbohydrates and caloric intake

•  High carbohydrate intake can lead to CO₂ buildup and ventilator problems

  RQ < 0.7 = ketosis and fat oxidation (starving)

•  Tx: ↑ carbohydrates and caloric intake

  Pure fat utilization – RQ = 0.7

  Pure protein utilization – RQ = 0.8

  Pure carbohydrate utilization – RQ = 1.0

POSTOPERATIVE PHASES

  Diuresis phase – postoperative days 2–5

  Catabolic phase – postoperative days 0–3 (negative nitrogen balance)

  Anabolic phase – postoperative days 3–6 (positive nitrogen balance)

STARVATION OR MAJOR STRESS (SURGERY, TRAUMA, SYSTEMIC ILLNESS)

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