NMS. Surgery

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Chapter 1 ♦ Principles of Surgical Physiology

b. Prealbumin has a shorter half-life and is more reflective of current status. c. A C-reactive protein (CRP) should be checked because elevated levels of inflammation (trauma/sepsis/burns) will alter visceral protein production away from prealbumin synthesis. C. Weight gain (poor method): Because most patients in the hospital are stressed, they tend to retain water and become edematous. Also, they will be catabolic and lose lean body weight despite the increase of their actual body weight from fluid. D. Observe the overall condition of the patient (best overall method): Obtain nitrogen balances (maximum of twice weekly), follow visceral proteins (prealbumin/CRP twice weekly), and increase protein administration. II. Enteral nutrition: Enteral nutrition maintains gut mucosal integrity and reduces complications. If unused for even brief periods, the gut mucosa begins to atrophy and lose its barrier function, leading to bacterial translocation and worsening systemic inflammation. In addition to translocation, the atrophied mucosa is unable to digest food. A. Formula compositions: When possible, patients should be fed by mouth; however, with critical illness, aspiration risk, depressed mental status, or inability to take adequate calories or protein orally, administration of enteral feeding formulas is often necessary. Nutritional formulas may be standard or specialized to serve the needs of unique patient populations. 1. Standard formulas: Provide a balanced calorie/protein ratio with ~50%–65% of calories from carbohydrates, 10%–20% from proteins, and the rest from fats. Caloric density is ~1.0–1.2 kcal/mL; they include the essential fats, minerals, and trace elements. 2. Elemental formulas: Amino acid-based for ease of digestion and lower residue in patients with short gut syndrome or distal enterocutaneous fistulas. 3. Calorie-dense formulas: Contain more calories per milliliter than standard formulas (typically 1.5–2.0 kcal/mL) for patients needing fluid restriction or very high caloric requirements. 4. Protein-dense formulas: Provide increased protein (20%–25% of calories) for patients with very high protein needs. 5. Fat-based formulas: Reduce CO 2 production for patients with compromised minute ventilation (e.g., severe chronic obstructive pulmonary disease [COPD] and acute respiratory distress syndrome [ARDS] patients). 6. Immunomodulating formulas: Provide glutamine and omega-3 fatty acids to enhance immunologic function with mixed efficacy. B. Administration route 1. Enteral nutrition formulas can be delivered by tubes placed into the GI tract directly (gastrostomy, feeding jejunostomy) or via the nose (nasogastric, nasoduodenal, or nasojejunal).