Nasoenteric tubes are the most commonly used means of providing enteral nutritional support in critically ill patients. This route is preferred for short- to intermediate-term enteral support when eventual resumption of oral feeding is anticipated. It is possible to infuse enteral formulas into the stomach using a conventional 16- or 18-French (Fr) polyvinyl chloride nasogastric tube, but patients are usually much more comfortable if a small-diameter silicone or polyurethane feeding tube is used. Nasoenteric tubes vary in luminal diameter (6 to 14 Fr) and length, depending on the desired location of the distal
orifice: stomach, 30 to 36 in.; duodenum, 43 in.; jejunum, at least 48 in. Some tubes have tungsten-weighted tips designed to facilitate passage into the duodenum via normal peristalsis; others have a stylet. Most are radiopaque. Some tubes permit gastric decompression while delivering formula into the jejunum.

Nasoenteric feeding tubes should be placed with the patient in a semi-Fowler’s or sitting position. The tip of the tube should be lubricated, placed in the patient’s nose, and advanced to the posterior pharynx. If the patient is alert and can follow instructions, the patient should be permitted to sip water as the tube is slowly advanced into the stomach. To avoid unintentional airway placement and serious complications, position of the tube should be ascertained after it has been inserted to 30 cm. Acceptable means of documenting intraesophageal location of the tube include a chest radiograph or lack of CO₂ detection through the lumen of the tube by capnography or colorimetry. If the tube is in the airway, CO₂ will be detected and the tube must be removed. Alternatively, commercial systems are now available to track tube progression from the esophagus through the stomach to the duodenum by electromagnetic means. Proper final placement of the tube in the stomach must be confirmed by chest or upper abdominal radiograph before tube feeding is begun. The following methods to assess final tube placement are unreliable and do not assess tube misdirection into the lower respiratory tract: auscultation over the left upper quadrant with air insufflation through the tube, assessment of pH with gastric content aspiration, and easy passage of the tube to its full length with the absence of gagging and coughing [21,22]. The tube should be securely taped to the nose, forehead, or cheek without tension.

Delayed gastric emptying has been confirmed in critically ill patients and may contribute to gastric feeding intolerance. One study randomized 80 critically ill patients to gastric feeding with erythromycin (200 mg IV every 8 hours as a prokinetic agent) or through a transpyloric feeding tube and identified that the two were equivalent in achieving goal caloric requirements [23]. Spontaneous transpyloric passage of enteral feeding tubes in critically ill patients is commonly unsuccessful secondary to the preponderance of gastric atony. The addition of a tungsten weight to the end of enteral feeding tubes and the development of wire or metal stylets in enteral feeding tubes are aimed at improving the success rate for spontaneous transpyloric passage. Once the tube is documented to be in the stomach, various bedside techniques including air insufflation, pH-assisted, magnet-guided [24], and spontaneous passage with [25] or without motility agents may help to facilitate transpyloric feeding tube passage.

IV metoclopramide and erythromycin have been recommended as prokinetic agents. But a Cochrane Database Systematic Review concluded that doses of 10 or 20 mg of IV metoclopramide were equally ineffective in facilitating transpyloric feeding tube placement [26]. No matter which techniques are used to facilitate transpyloric passage of enteral feeding tubes, these tubes must be inserted by skilled practitioners using defined techniques [27,28].

If the tube does not pass into the duodenum on the first attempt, placement can be attempted under endoscopic assistance or fluoroscopic or electromagnetic guidance. The latter method requires specialized equipment. Endoscopic placement of nasoenteral feeding tubes is easily accomplished in the critically ill patient and can be performed at the bedside using portable equipment [29,30,31,32,33]. Transnasal or transoral endoscopy can be used for placement of nasoenteral feeding tubes in critically ill patients [33]. The patient is sedated appropriately (see Chapter 20), and topical anesthetic is applied to the posterior pharynx with lidocaine or benzocaine spray. A 43- to 48-in.-long nasoenteric feeding tube with an inner wire stylet is passed transnasally into the stomach. The endoscope is inserted and advanced through the esophagus into the gastric lumen. An endoscopy forceps is passed through the biopsy channel of the endoscope and used to grasp the tip of the enteral feeding tube. The endoscope, along with the enteral feeding tube, is advanced distally into the duodenum as far as possible (Fig. 16.1).

The endoscopy forceps and feeding tube remain in position in the distal duodenum as the endoscope is withdrawn back into the gastric lumen. The endoscopy forceps are opened, the feeding tube released, and the endoscopy forceps withdrawn carefully back into the stomach. On first pass, the feeding tube is usually lodged in the second portion of the duodenum. The portion of the feeding tube that is redundant in the stomach is advanced slowly into the duodenum using the endoscopy forceps to achieve a final position distal to the ligament of Treitz (Fig. 16.2). An abdominal radiograph is obtained at the completion of the procedure to document the final position of the nasoenteral feeding tube. Endoscopic placement of postpyloric enteral feeding tubes is highly successful, eliminates the risk of transporting the patient to the radiology department for fluoroscopic placement, and allows prompt achievement of nutritional goals because enteral feeding can be initiated immediately after the procedure.

The recent development of ultrathin endoscopes (outer diameter 5.1 to 5.9 mm vs. 9.8 mm in standard gastroscope) has enabled nasoenteric feeding tube placement via transnasal endoscopy using an over-the-wire technique. A 90% success rate was documented with endoscopic procedure duration of approximately 13 minutes, shorter than fluoroscopic procedure duration and without the need for additional sedation [34]. Unsedated transnasal ultrathin endoscopy can also be used for feeding tube or percutaneous endoscopic gastrostomy (PEG) placement in patients who are unable to undergo transoral endoscopy, that is, those who have partial or complete occlusion of the mouth [35].