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Nutrition Basics
• Appropriate nutritional support has been recognized in recent years to be of key importance for favorable outcomes in patients with critical illness.
• Dietary fats and carbohydrates normally supply most of the body’s energy requirements for cellular function. Dietary proteins provide amino acids for protein synthesis, and amino acids can also function as energy substrates.
• Healing of wounds requires energy, protein, lipids, electrolytes, trace elements, and vitamins. Depletion of any of these substrates may delay wound healing and predispose to infection.
• Patients with critical illness should undergo whatever initial hemodynamic resuscitation they require before initiation of nutritional support. Absorption, distribution, and metabolism of nutrients require tissue blood flow, oxygen, and carbon dioxide removal.
Perioperative Nutrition Considerations
• Malnourished patients benefit from nutritional repletion via either enteral or parenteral routes before elective surgery.
• Current guidelines and current published evidence support continuing enteral nutrition (EN) infusions (particularly when they are delivered distal to the pylorus) perioperatively and intraoperatively.
• For patients on total parenteral nutrition (TPN), metabolic abnormalities should be corrected preoperatively. For example, hypophosphatemia is a serious and often unrecognized complication that can contribute to postoperative muscle weakness and respiratory failure. Frequent glucose monitoring is needed regardless of whether the TPN infusion is continued, reduced, or replaced.
• Administering a carbohydrate “load” to nondiabetic patients shortly before surgery favorably increases plasma insulin concentrations and decreases postoperative insulin resistance.