Enteral Feeding Tube Placement

Initiating Nutritional Support

Nutritional support should be considered for all patients according to clinical assessment and guidelines over the perioperative period ( Box 64-1-1 ). If a surgical intervention can be delayed, 10 to 14 days of nutritional support for patients with severe nutritional risk has been shown to be beneficial prior to surgery. Obviously critical patients and those with a significant loss in body weight or a premorbid state should receive support almost immediately (<3 days) after admission, because they often exhibit immunologic impairment and are at increased risk of infection. Significant weight loss in these patients is often associated with a reduced chance of survival. Malnourished surgical patients also have severely impaired wound healing times. In addition to requiring nutritional support, severely hypercatabolic patients may require therapeutic interventions and rehabilitation exercise programs to regain muscle mass.

Enteral Nutrition

Early (24 to 48 hours) institution of EN following major surgery minimizes the risk of undernutrition and can abate the hypermetabolic response seen after surgery. Administration of EN can be accomplished via various routes, including the use of nasogastric (NG), nasoduodenal, and nasojejunal tubes ( Fig. 64-1-2 ), which are preferentially used in patients who are expected to require support for short time periods (<4 weeks). Other surgical options include open or percutaneous gastrostomy and jejun­ostomy, usually for those patients who are expected to require long-term EN (>4 weeks). In general, EN offers the beneficial effects of trophic feedings, which include structural maintenance and functional support of the intestinal mucosa, achieved by providing nutrients such as glutamine, preserving blood supply, and promoting peristalsis. Use of EN to protect and maintain the integrity of the intestinal mucosa may therefore help reduce the risk of sepsis caused by bacterial translocation. Feeding routes for the delivery of EN are described in Table 64-1-1 .

In the critically ill patient, EN should be initiated within 48 hours of injury or admission; average intake delivered within the first week should be at least 60% to 70% of the total estimated energy requirements, as determined by the assessment. Provision of EN in this time frame and at this level may be associated with decreased length of hospital stay, days on mechanical ventilation, and infectious complications.

Feeding through a NG tube is the most cost-effective method for EN support and perhaps the most helpful for preventing postoperative complications, such as gastroparesis. The use of NG tubes conveniently facilitates the ability to supply caloric needs and to monitor the volume of gastric residuals. To decrease reflux and the risk of aspiration, it is recommended that the head of the bed be raised to 45 degrees and the volume of residuals not exceed 50 mL/hour. Although the residual volume should be rechecked after 1 hour from a single elevated value, feeding does not have to stop automatically.

GI ileus may reflect an underlying deterioration; therefore, monitoring gastric residual volumes serves as an indicator of intercurrent conditions, such as sepsis. In burn patients, residuals that increase above the amount of food delivered routinely every hour have been shown to correlate with the development of bacterial sepsis, and a full sepsis workup is indicated when gastric residuals exceed 200 mL.

The practice of checking the positioning of tubes by X-ray prior to their use is a time-consuming process that has been motivated, in part, by the unintended placement of small-diameter tubes into lower airways. However, NG tubes may be placed with confidence by auscultation over the stomach while delivering 50 mL of air quickly with an irrigation syringe. Nasojejunal and duodenal tubes may be too small for this procedure. Contraindications to EN include prolonged ileus or gastroparesis, bowel obstruction, acute pseudo-obstruction, ischemic enterocolitis, and other causes of malabsorption.

With nasoenteric feeding beyond the stomach, the tube should be advanced through the duodenum, ideally past the ligament of Treitz to the proximal jejunum, because this reduces the risk of aspiration. Nasojejunal feeding may be preferable in some settings because it does not need to be stopped prior to surgery to prevent aspiration. However, nasojejunal feeding requires continuous infusion, and gastric residual volumes cannot be checked to confirm progress. Nasojejunal feeding should not be commenced until the patient is fully volume-resuscitated and hemodynamically stable. Percutaneous feeding options should be considered if a patient requires nasal tube feeding for a prolonged period beyond 2 or 3 weeks.

Ileus associated with severe injury is not as common as previously thought. Ileus derived from mesenteric hypoperfusion prior to adequate resuscitation is reversed once the patient has been resuscitated. Conversely, over-resuscitation leads to GI edema and should also be avoided. Postinjury ileus does not affect the small bowel as profoundly as the stomach. Therefore, feeding using a nasoduodenal tube passed through the pylorus, or a nasojejunal tube advanced past the ligament of Treitz, can be initiated as soon as possible, preferably within 6 hours following injury. This approach also allows continuous feeding during surgeries and physical therapy sessions. The initiation of immediate enteral feeding allows the delivery of calculated caloric requirements by the third day postinjury. Reduction of hypermetabolism by initiating enteral feeding soon after injury is possible, with this reduction in metabolic rate associated with less intense elevations in glucagon, cortisol, and catecholamine levels.