Surgical Nutrition Quiz

Starvation

• Acute starvation: energy supplied via glycogen stores in liver and muscle (first 12-72 hours)
• Proteolysis (alanine and glutamine) and hepatic gluconeogenesis occur during acute starvation
• Brain, RBC, retina, and renal medulla require glucose for energy

Prolonged Starvation

• Body shifts to lipolysis for protein sparing
• Free fatty acids converted to ketones, potentially leading to acidosis/toxic conditions

Metabolic Response to Injury – Ebb and Flow

Ebb

• Starts immediately after injury, lasts hours to days
• Hypometabolism and tissue hypoperfusion occur
• Increased sympathetic activity and hypothalamic pituitary axis output
• Catecholamines (e.g., norepinephrine) are released to compensate
  • Increases cardiac contractility, heart rate, and vasoconstriction

Flow

• Period 3-10 days after injury; catabolic state
• Hypermetabolism and tissue hyperperfusion for healing
• Elevated insulin counteracted by concurrent elevated levels of catecholamines, glucagon, and cortisol
  • Results in net loss of proteins (negative nitrogen balance)
• Stress hyperglycemia due to accelerated gluconeogenesis and insulin resistance

Protein Malnutrition

• Marasmus: deficiency in all macronutrients (proteins, carbohydrates, fats)
• Kwashiorkor: deficiency in proteins
  • Albumin < 2.5 associated with increased mortality, length of hospitalization, healthcare costs, and rate of readmission

Macronutrients – Carbohydrates

• Function: energy and digestion
• Brain and RBC require glucose for energy
• Limited stores as glycogen, excess converted to fats
• Supplied via gluconeogenesis during hypermetabolic states
• Daily intake: 120g/day

Macronutrients – Proteins

• Function: building blocks – repair/build tissues
• Also functions in immunity, enzymes, transport, hormones, fluid balance, and energy
• All protein in body is functional, not considered storage of energy
• Types: Essential, Non-essential, & Conditionally Essential
• Daily intake: 1.5-2 g/kg/day

Important Amino Acids

• Glutamine:
  • Most abundant amino acid (50% of free amino acid pool)
  • Primary fuel source for small intestine enterocytes
  • Conditionally essential during illness
• Arginine:
  • Functions in tissue metabolism, growth, repair
  • Substrate for nitric oxide (NO) production
  • Important for maintaining vascular tone, coagulation cascade, immunity, etc.

Macronutrients – Lipids

• Functions: energy -active and stored, insulation & organ protection, structure – hormones, cell membranes, nerve tissues, absorption – Vitamins ADEK, phytochemicals
• Types: Essential (Linoleic & Alpha-Linolenic), Non-essential, Saturated (bad), & Unsaturated (mono & polyunsaturated)
• Daily intake: 10-30% of total daily caloric load (2-4% essential)

Micronutrients

• Vitamins, electrolytes, minerals, metals
• Prebiotics: indigestible fiber, feeds gut microbiome
• Probiotics: live, good bacteria, yogurt & cheese
• Water

Nutritional Assessment

• Assessment through history, physical exam, labs, bioimpedance, indirect calorimetry, anthropometric measurements, predictive formulas
• Detailed history and physical exam remains a primary nutritional assessment tool
• Patients should be screened for risk factors and comorbidities, considering the magnitude of proposed surgical procedure

Assessment – History

• Screen for weight changes
  • Unexplained weight loss > 5% in one month or 10% in 6 months associated with increased postoperative complications
• Medications: many have nutritionally related side effects or increased nutrient requirements
• Past medical/surgical history