ICU Nutrition

ICU nutrition management addresses the hypermetabolic, catabolic state of critical illness, where inadequate nutritional support leads to rapid skeletal muscle wasting (up to 1 kg/day of lean mass), impaired immune function, poor wound healing, prolonged ventilator dependence, and increased mortality. The metabolic response to critical illness occurs in two phases: the acute/ebb phase (first 24-48 hours — characterized by decreased metabolic rate, insulin resistance, and mobilization of endogenous fuel stores) and the flow/catabolic phase (days 3-7+ — hypermetabolism with dramatically increased energy expenditure, protein catabolism, and negative nitrogen balance). Enteral nutrition (EN) is strongly preferred over parenteral nutrition (PN) because it maintains gut mucosal integrity, prevents bacterial translocation (gut barrier failure allows bacteria to enter the bloodstream, potentially causing sepsis), preserves gut-associated lymphoid tissue (GALT) immune function, and reduces infectious complications. EN should be initiated within 24-48 hours of ICU admission in hemodynamically stable patients. Trophic feeding (10-20 mL/hour) is acceptable in the first 48-72 hours, advancing to goal rate over 48-72 hours. Gastric feeding is standard; post-pyloric (jejunal) feeding is reserved for patients with high gastric residual volumes (GRV)...