If aspiration remains a problem despite the changing of delivery schedules, duodenal or jejunal feeding tubes may be required. These tubes can be placed by either nasal intubation or percutaneous endoscopic procedures. Other measures can also be taken to lessen the chance for aspiration, including elevating the patient's upper body to a 30- to 45-degree angle. In a bedridden patient, this can be accomplished simply by raising the head of the bed; sacral decubitus precautions should be taken. Drugs that enhance gastric motility, such as metoclopramide (Reglan), cisapride (Propulsid) or erythromycin, can also prevent aspiration.

Although the intermittent method of feeding more closely mimics normal feeding patterns, other problems, such as abdominal distention, diarrhea, constipation and delayed gastric emptying, are more common with this method than with the continuous feeding regimen

Initiation of Feeding

Once the enteral formula, tube type and size, and feeding schedule are determined, the proper method of beginning enteral feeding must be mastered. For patients who have not been fed for a prolonged time, it is very important that feedings be unplemented slowly, to reacquaint the gastrointestinal tract with the handling of food. Of the multiple regimens used to initiate enteral feeding, three wir be discussed here. Two of the regimens use continuous enteral feedings with a pump.

One useful regimen that appears to yield promising results recommends beginning with a hypotonic (0.5 calorie per mL) solution, with progression to a hypertonic solution. The 0.5 calorie per mL solution is started as a continuous infusion at a rate not exceeding 30 to 50 mL per hour. The volume can be increased by 25 to 50 mL per hour every six to 24 hours, until the volume goal for the patient is met. Once the volume goal is met, the formula can be slowly switched from 0.5 calories per mL to 0.75 calories per mL and, finalfly, to 1.0 calories per mL (full strength). Although there are some theoretic advantages to the use of hypotonic (or diluted) formulas, no evidence shows that gastrointestinal intolerance is lessened with this method.

The second continuous enteral feeding regimen is more aggressive. It begins with 1.0 calorie per mL formula given at an initial rate of 50 to 75 mL per hour. Gastric residuals are checked after the first three to four hours and, if residual volume is less than 100 mL, the feeding rate is advanced by 25 mL per hour every six to 12 hours, as tolerated. Using this method, the full volume target can usually be achieved within 72 hours.

For intermittent formula administration, either isotonic or hypertonic formula can be chosen. However, only one-half to one-fourth of the final volume should be delivered initially over 30 to 45 minutes. This rate can be repeated every four hours with subsequdnt residual checking. Advancement to full volume can be completed within 48 to 72 hours if no signs of gastrointestinal intolerance, such as vomiting or diarrhea, occur. A number of other feeding regimens have been described elsewhere; however, no studies have directly compared the different schedules.

Monitoring Nutritional Status

Nutritional status monitoring is normally accomplished using accurate patient weights, intake and output volume data, and routine laboratory screening, including serum glucose and electrolyte levels and hematologic markers. The traditional indicator for protein metabolism has been serum albumin. Although serum albumin may be an accurate marker of long term nutritional status, it is of limited value in assessing acute nutritional changes because of its long half-life (18 to 20 days). Serum prealbumin, which has a half-life of approximately 36 hours, may be a better indicator of short-term protein metabolism and acute changes in nutritional status. Nutritional anemia--a serum transferrin level under 2 g per L--and a decrease in the total lymphocyte count below 1,200 cells per mL are also indicators of chronic nutrition problems.