Admission to the Intensive Care Unit)
Begin nutrition support Premorbid BMI >18.5
and <10% weight loss
Premorbid BMI <18.5 or >10% weight loss
Dextrose containing IVF
NPO >7 days or change in
clinical situation Determine route and
caloric/protein needs Length of expected NPO status
<7 days to oral feeds >7 days to oral feeds
NPO, nothing by mouth; BMI, body mass index; IVF, intravenous fluids.
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TABLE 71.2 Needs Estimated on Body Mass Index (BMI)
BMI Energy (kcal/kg/day)
<15 35–40
15–19 30–35
20–25 20–25
26–29 15–17
29 15a
aDo not exceed 2000 calories per day for obese patients, allowing for mobilization of adipose stores for energy.
profile, magnesium, phosphate (for renal function and risk of refeeding syndrome), hepatic panel, and complete blood count.
Plasma albumin and prealbumin have a low sensitivity and specificity to changes in nutrition intake in the hospitalized patient. Both are affected by a plethora of factors.
Levels are increased by corticosteroids, insulin, thyroid hormone, and dehydration. In contrast, levels are decreased by inflammatory mediators, severe liver and renal disease, malabsorption, and intravascular volume overload. In short, albumin and prealbumin levels in the critically ill patient reflect changes in protein synthesis, degradation, and distributive losses that are reflective of critical illness, not nutritional status.
Several equations exist to determine resting energy requirements in humans. The American Dietetics Association studied the reliability and validity of several predictive equations in a variety of hospitalized patients. These equations generate values within 10% of measured values in healthy subjects when compared with indirect calorimetry with a reliability of 70%. However, they are much less accurate in persons who are at extremes in weight or who are critically ill. Only two equations are designed for use in the critically ill patient, the 1992 Ireton-Jones equation and the 1998 Penn State equation; however, both are cumbersome to complete.
A more simple method for estimating caloric requirements in hospitalized patients has been developed using BMI (Table 71.2). The lower range in each category should be considered for initiation of nutrition support in insulin-resistant critically ill patients to decrease the risk of hyperglycemia and infection associated with overfeeding. In the critically ill obese patient (BMI≥30) permissive underfeeding or hypocaloric feeding is recommended.
In general, protein needs are based on kilograms of ideal body weight, which can be determined using the Hamwi method (Table 71.3). The increased metabolic rate associated with critical illness along with several other potential factors including
TABLE 71.3 Hamwi Method to Determine Ideal Body Weight Calculate ideal body weighta:
Men: 106 pounds for first 5 feet plus 6 pounds for each inch above 5 feet Women: 100 pounds for the first 5 feet plus 5 pounds for each inch above
5 feet
aConversion from pounds to kilograms: pounds÷2.2.
Nutrition in the ICU rNutrition in the Intensive Care Unit 5 6 3
TABLE 71.4 Recommended Daily Protein Intakea
Clinical condition Protein needs (g/kg IBW/dayb
Normal (nonstressed) 0.75
Critical illness/injury 1.00–1.50
Acute renal failure (undialyzed) 0.80–1.00
Acute renal failure (dialyzed) 1.20–1.40
Peritoneal dialysis 1.30–1.50
Burn/sepsis 1.50–2.00
CVVHD 1.70–2.50
aClinical conditions are not additive; to calculate needs, use value that prescribes the highest protein needs.
bLower protein requirements may be necessary in hepatic encephalopathy.
IBW, ideal body weight; CVVHD, continuous venovenous hemodialysis.
renal failure, extent of injury, presence of significant burns, and sepsis may significantly increase the requirements for protein (Table 71.4).
Once the decision to begin nutrition support has been made, the optimal delivery route needs to be determined and feeding initiated (Algorithm 71.2). At present, the general consensus is to feed enterally whenever possible.
Enteral nutrition may be beneficial in protecting gut mucosal integrity by main- taining villous height and supporting IgA producing immunocytes which comprise the gut-associated lymphoid tissue (GALT). Loss of integrity in the intestinal lumen may lead to the migration of bacteria to the portal and systemic circulation, thereby increasing the risk of systemic infection and potential for multi-organ dysfunction syn- drome (MODS). If use of the enteral route is not feasible, total parenteral nutrition (TPN) should be considered as soon as possible in patients with evidence of protein–
calorie malnutrition; or after 7 days in previously well-nourished patients. Each route has advantages and disadvantages and conditions in which it is contraindicated (Table 71.5).
Either gastric or small bowel feeding is acceptable in the ICU setting. In critically ill patients with gastric feeding intolerance (patient complaints of pain, vomiting, abdominal distention, or gastric residual>500 mL) placement of a small bowel feeding tube should be considered. Delivery of enteral feeding into the small bowel has been recommended as a strategy to reduce the risk of aspiration; however, randomized controlled studies of gastric versus small bowel feeding in ICU patients have been inconclusive. Unfortunately, patients who had significant risk factors for aspiration or who had gastric feeding intolerance were excluded from these studies. These patients may benefit from placement of a postpyloric feeding tube (Table 71.6). Although the short-term addition (24 to 72 hours) of prokinetic agents such as metoclopramide and erythromycin has been shown to temporarily improve gastric emptying and EN tolerance, longer use may lead to drug induced complications. Patients with severe acute pancreatitis fed via a small bowel feeding tube, as opposed to TPN, have been shown to have reduced infectious morbidity. Whether the tube feeding is provided pre- or postpyloric, other than increased gastric residual volume, the recommendations to troubleshoot complications are the same (Table 71.7).
The appropriate type of tube feeding formula to use in the critically ill patient continues to be debated. Based on the current evidence, whole-protein formulas are
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