the mouth with the gastroscope. The wire is looped around the PEG tube and pulled through the

abdominal wall in an antegrade fashion, until only the head of the feeding tube remains in the stomach,

with the rest of it being extracorporeal. The inner part of the PEG tube is confirmed to be in correct

position and the feeding tube is secured in place. This technique may be difficult in obese patients,

whose abdominal walls can be hard to transilluminate. Modified laparoscopy-assisted techniques have

also been described.

Feeding jejunostomies can be considered following any major abdominal procedure, if the need for

prolonged enteral nutrition is anticipated. A loop of proximal small bowel, typically 20 to 40 cm distal

to the ligament of Treitz is elevated and secured against the abdominal wall fascia of the left upper or

lower quadrant and is accessed transabdominally with a feeding tube. The tube can be covered for a

short distance with bowel serosa (Witzel jejunostomy). Laparoscopic feeding jejunostomies have also

been described, as well as the passage of jejunostomy tubes through percutaneously placed gastrostomy

tubes.

ADDITIONAL NUTRITIONAL CONSIDERATIONS

Infectious Processes and Fever

As mentioned earlier, with core temperature elevations, such as those that occur with fever during

infectious or other inflammatory processes, the base metabolic rate increases. Total energy

requirements can be calculated using the aforementioned equations, multiplying by appropriate factors:

mild to moderate infections increase energy requirements by 20% to 30%, and severe infection with

fever increases caloric needs by over ∼50% above basal levels. Even though weight gain and anabolism

are difficult to achieve during the septic response, the astute clinician should be mindful of these

associations and adjust nutritional support accordingly in persistently febrile patients.

Respiratory Failure

A condition commonly complicating surgical patients is respiratory failure with the need for prolonged

mechanical ventilation. The main concern in mechanically ventilated patients is adequate gas exchange,

which includes oxygen and carbon dioxide transport across the capillary–alveolar membrane. Not

uncommonly the indication for ventilatory support is pulmonary infection, which along with a

postoperative status, contributes to the overall hypermetabolism. Hypermetabolism is accompanied by

increased oxygen consumption, which drives carbon dioxide production, as more substrate must be

oxidized to support the greater energy requirements. While nutrition commonly takes lower priority in

ventilated patients, in whom all efforts are directed toward managing the underlying etiology for the

respiratory insufficiency, consideration should be given to the content of the nutritional support, as they

may facilitate or prolong weaning, especially in those with chronic CO2

retention. The RQ of a specific

nutrient denotes the carbon dioxide produced over oxygen consumed, and adjustments in feedings from

high RQ (e.g., carbohydrates, RQ = 1) to lower RQ (e.g., fat, RQ = 0.7), and avoidance of overfeeding

should be considered in patients difficult to wean due to CO2

retention. These adjustments have to be

considered carefully, as increased fat intake, especially mixtures high in n-6 fatty acids, may exacerbate

lung injury.

Renal Failure

Renal failure affects the body’s ability to clear the byproducts of protein metabolism, but does not

change the catabolic rate or the protein requirements. Therefore, a careful balance needs to be achieved

between the need for protein and to limit uremia. When acute surgical stress is superimposed,

consideration for potentially earlier or more aggressive renal support should be given, so that the body

is not restricted of protein, which is critical during the hypermetabolic phase of acute disease. TPN with

amino acids of high biologic value may improve survival in patients with acute renal failure.104 The use

of solutions containing high-quality amino acids can improve nitrogen balance and minimize urea

production. This translates into a decreased frequency of dialysis.

Liver Failure

Patients with liver disease may be malnourished secondary to excessive alcohol intake, diminished food

intake, or persistent inflammatory state from viral infection. These individuals are protein depleted, yet

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tolerate protein poorly, due to their likelihood to become encephalopathic with high-nitrogen intake.

Due to liver damage and portosystemic shunting, these patients develop derangements in circulating

levels of amino acids. The plasma aromatic-to-branched chain amino acid ratio is increased, favoring the

transport of aromatic amino acids across the blood–brain barrier. These amino acids are precursors of

neurotransmitters that can worsen encephalopathy and lethargy. Using solutions enriched in BCAAs and

deficient in aromatic amino acids in liver failure patients enhances protein tolerance and potentially

improves in clinical encephalopathy.

Heart Failure

Myocardial dysfunction can be seen as part of the critical illness cardiomyopathy (circulating cytokines

TNF and IL-1 appear to have a direct myocardial depressant activity) in patients with sepsis or those

with preexisting congestive cardiac failure who undergo surgery. Patients with surgical emergencies

commonly third space and require significant amounts of crystalloid resuscitation, which may

exacerbate their pre-existing volume overload. When considering nutritional support of these patients,

efforts should be made to minimize the total fluid volume, and nutrition formulas should be

concentrated if possible.

Bariatric Surgery

Bariatric patients pose a special challenge, given their chronically overnourished status and their altered

gastrointestinal tract, if they have undergone weight loss surgery. The latter are at increased risk for

several macro- (usually protein) and micronutrient deficiencies (most commonly vitamins D and B12

,

calcium, iron, folic acid, zinc, and selenium),105–107 and the clinician should be mindful of these

potential complications. Nutritional support of the obese or postweight loss surgery patient is

particularly complex because of the balance needed between minimizing overfeeding and avoiding the

hypercatabolic state. Despite the excessive fat stores, critically ill obese patients should receive early

and timely nutrition, as protein–calorie malnutrition does occur, and consideration for indirect

calorimetry, which allows accurate estimation of the caloric requirements, and early involvement of a

nutritionist should be considered. Hyperglycemia is an additional concern in obese patients, as glucose

intolerance or frank diabetes may first manifest in acute illness, and should be addressed whenever

identified.108

Geriatric Patients

Attention to appropriate nutritional support of the geriatric patient is of paramount importance, both in

the perioperative stage, as well as in the ICU, given the multiple physiologic alterations seen in older

age, including greater ratio of fat-to-muscle mass, decreased cardiac and pulmonary reserves, poor

dentition, polypharmacy, and high incidence of malnutrition, which may be as high as 85% in nursing

home residents.109,110 In relation to preoperative preparation, elderly patients are more likely to have

numerous disease processes affecting their general nutritional status, including diabetes, cancers,

cardiac, pulmonary, and renal insufficiency. Given a certain degree of lean body mass loss is to be

expected in this demographic, a higher-protein intake (>1.5 g/kg/day) should be the goal

preoperatively in the elderly undergoing elective surgery, or early in the recovery phase after

emergency procedure or acute surgical illness.46 Toward that goal, numerous protein-rich supplements

that are commercially available to patients who can tolerate enteral feedings, or parenteral nutrition

with high-protein concentrations can be prescribed.44

Enterocutaneous Fistulas

Gastrointestinal cutaneous or gastrointestinal atmospheric fistulas with high output (commonly defined

as having output greater than 400 cc/24 hours) represent a classic indication for long-term TPN. Oral

intake in patients with such fistulas typically results in greater output, especially in fistulas involving

the proximal gastrointestinal tract, which can lead to dehydration, significant metabolic disturbances,

and adversely affect the ability of the fistula to heal. TPN has been shown to increase spontaneous rate

of closure of enterocutaneous fistulas by improving overall nutritional status in the host, or improving

perioperative outcomes in those requiring surgical therapy. Somatostatin and analogs have been used to

aid with fistulous output and spontaneous closure with varying results.

Short Bowel Syndrome

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Patients with history of extensive small bowel resection lose a large part of the absorptive ability of the

bowel, and frequently have to rely on prolonged TPN to meet their nutritional goals. In select patients

with residual small intestine of at least 18 inches, postresection hyperplasia that can allow enteral

nutrition has been demonstrated in subjects treated with supplemental glutamine, growth hormone, and

a high-carbohydrate, low-fat TPN.111

Major Thermal Injury

Burn victims often suffer from prolonged ileus, which encumbers enteral nutritional support. Even if the

bowel is usable and patients not on mechanical ventilation, they are frequently unable to consume

adequate calories, due to anorexia of severe injury and frequent npo status for repeated trips to the

operating room. Currently available data suggest that aggressive nutritional support with high-protein

intake in patients with major burns is associated with improved survival.112

Prolonged Postoperative Ileus

Patients undergoing major gastrointestinal procedures may develop prolonged ileus in the postoperative

period, which precludes the use of the intestinal tract as a feeding route. If the patient is unable to eat

by postoperative days 5 to 7, TPN should be considered. Although provision of TPN does not influence

the disease process per se, it is beneficial because it prevents further erosion of lean body mass. When

postoperative ileus of shorter duration is anticipated, patients can be bridged with PPN.

Acute Radiation and Chemotherapy Enteritis

Malnourished patients who receive abdominopelvic radiation or chemotherapy may develop mucositis

and enterocolitis that precludes using the intestinal tract for nutrition for variable periods of time. In

such individuals, parenteral nutrition should be provided, until the enteritis resolves and oral feedings

can be resumed.

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