Protein needs are certainly heightened during critical illness, although no consensus or evidence exists to suggest the best method for determining protein needs. Protein needs are generally assumed to be in the 1.2 to 2.0 g/kg/day range for metabolically stressed patients (AND, 2015a). A.S.P.E.N. guidelines recommend protein needs in the 1.2 to 2.0 g/kg/day range for those with BMI < 30, and acknowledge that protein needs may be even higher in cases of burns or multi-traumas (McClave et al. 2009). The Dietary Reference Intake (DRI) for healthy adults for protein is 0.8 g/kg/day (Institute of Medicine 2005). General guidelines suggest increasing protein include: Determining Fluid Needs Fluid needs in critical care are individualized based on factors that include volume depletion, degree of endothelial injury and capillary leak, and varying levels of cardiac and renal function (AND, 2015a). General fluid guidelines are estimated at 30 ml/kg/day, but hypovolemia, renal status, and cardiac function all mandate individualization of therapy. It is unlikely that enteral formulas alone will meet fluid needs, and additional water via oral, intravenous, or enteral routes is most often required to meet needs. [gallery ids="225657,225658,225659,225660,225661,225662,225663,225665,225664,225666,225667,"] Nutrition Support in Critical Illness The timely initiation of aggressive nutrition support helps maximize outcomes in critically ill patients. “Timely” is key and a primary nutrition intervention should be initiation of enteral nutrition early on at the 24 to 48 hour mark to attenuate the stress response. Feeds are started at 10 to 30 ml/hr and gradually advanced to goal rates within the next 48 to 72 hours (AND, 2015a). A.S.P.E.N. guidelines recommend achieving 50 to 65 percent of goal nutrition intake by the end of the first week. After the end of the seven to ten days, if enteral feeds are insufficient to meet total calorie needs, consider initiating supplemental parenteral nutrition (PN). In patients with a functioning gut, early initiation of enteral nutrition (EN) helps to maintain gut integrity, reduces oxidative stress, and regulates systemic immunity (Heyland and McClave, Chaper 11. Nutrition in the Critically Ill. 2005). Gastric access for EN is preferred, but if stomach feedings are not tolerated, duodenal or jejunal access is appropriate when gastric residuals are >200 ml on two or more occasions despite the use of prokinetic agents (McClave et al. 2009). The head of the bed should be elevated 45 degrees to prevent aspiration in patients receiving tube feedings. Formulas are preferably high in protein, low in total fat, with at least
25 percent of fat coming from medium-chain triglyceride (MCT), and the formula should contain at least 100 percent of the daily recommended intake DRI of vitamins and minerals as well as adequate amounts of soluble dietary fiber. The Academy of Nutrition and Dietetics makes limited recommendations regarding immunonutrition formulas. The Canadian guideline, guidelines from A.S.P.E.N. and European Society for Parenteral and Enteral nutrition all give more favorable recommendations for these types of formulas based on more recent research findings (AND, 2015a), (Heyland, Dhaliwal et al. 2003), (McClave et al. 2009), (Krey-mann et al. 2006).
For optimal outcomes, nutrition support and the tolerance of EN or PN should be closely monitored. Complications of nutrition support may be gastrointestinal in nature, may increase the risk of aspiration, and can result in fluid imbalances or hyperglycemia. Diarrhea is the most common complication of EN and occurs as a result of medication, use of hypertonic solutions, or antibiotic use that kills beneficial bacteria. The primary approach to managing diarrhea with EN should be a review of the medication list. Initiation of supplemental soluble fiber may also be beneficial.