Nursing Consideration While Placing Enteral Tube
Enteral Tube placement
An enteral tube is defined as any small-bore tube passed through the nose or mouth into the stomach or small intestine for the purpose of decompression, medication instillation, or feeding.
Because safety issues related to enteral
tubes that can be passed directly through the wall of the stomach or jejunum
are different, only the issues surrounding nasogastric/orogastric (NG/OG) tubes
and nonintentional (NI) tubes will be discussed.
Tube Insertion in Statistical
It is estimated that approximately one million enteral tubes are placed in adults and children in the United States annually (Metheny, Spies, & Eisenberg, 1986). Feeding by NG/OG/NI rubes is preferred when the gastrointestinal (GI) system is functional and the need for assisted feeding is expected to be short term.
Enteral feeding is physiologic, achieves a positive nitrogen balance sooner than royal parenteral nutrition, enhances gut healing, and reduces bacterial translocation, and also is less costly and is associated with low rates of sepsis.
Even in clients maintained primarily by total parenteral
nutrition, small amounts of nutrients are fed into the lumen of the gut through
enteral tubes to maintain the structure and function of the small intestine.
For many clients, feeding by NG/OG/NI tubes remains an essential life-saving
procedure.
Error In Insertion
Previous studies found NG/OG/NI tube placement errors to be common, with prevalence rates of errors in adults ranging from 1.3% to 89.5% depending on how narrow or broad the definition of error was ( McWey , Curry, Schabel , & Reines , 1988; Niv & Abu Avid, 1988).
Studies in children show that between 20.9%
and 43.5% of enteral tubes are placed incorrectly when placement error is
broadly defined ( Ellert & Beckstrand , 1999; Ellett , Maas, & Forsee ,
1998). Although estimates of error rates vary, there is no doubt that they
are common.
Errors in Placement of Tube
Errors in placement of NG/OG feeding tubes, which include initial erroneous placements as well as displacements over time, can lead to serious complications. If a tube ends in the airway, feeding through the tube will result in pulmonary aspiration or other pulmonary complications.
Feeding through a tube ending in the esophagus increases the risk of pulmonary aspiration. When an NG/ OG tube erroneously passes into the duodenum and the client is fed formula requiring both gastric and pancreatic enzymes for complete digestion, malabsorption that results in inadequate weight gain (or weight loss), diarrhea, and possibly dumping syndrome may occur.
Increasing the safety of NG/OG feeding requires knowledge development in at least two areas-predicting the insertion distance for correct tube placement and determining tube position. The state of the science regarding each of these knowledge needs will be reviewed.
At present no methods have been shown empirically to be adequate for predicting correct tube insertion length. The one adult study (Hanson, RL, 1979) concluded that use of the direct nose-ear-xiphoid (NEX) distance to determine the insertion length, the standard measurement used in practice, was not accurate.
Hanson recommended
a formula (INEX-50 cm/2 + 50 cm) adapted from his regression equation on NEX,
which in his sample was 91.4% accurate for estimating the distance for placing
the NG tube tip correctly in the stomach.
Insertion Length Estimation
Only a few studies have addressed insertion-length estimators in children. Ziemer and Carroll (1978) found at autopsy in infants that an NG tube inserted using the NEX distance almost always reached just past the lower esophageal sphincter and needed to be advanced a few centimeters for correct placement in the stomach.
They proposed that a more accurate method would be using the length from the tip of the nose to the lobe of the ear to a point midway between the xiphoid process and the umbilicus (NEMU).
Webley, Adamson, Clinkscales, Curran, and Bramson (1987) found on radiograph that. 55.6% of NG/OG tubes in 30 premature infants were incorrectly placed using the NEX distance and 39.3% of NG/OG tubes were incorrectly placed using the NEMU distance.
All of these errors involved high placements (which, if in the respiratory tract or the esophagus, often result in serious complications, such as aspiration pneumonia or parenchymal perforation with resulting pneumothorax).
Surprisingly, however, in spite of the evidence from these studies, a telephone survey of 113 Level II and III nurseries in five midwestern states found that 98% of nurses continued to use NEX to calculate tube insertion distance ( Shiao & DiFiore, 1996 ).
Beckstrand and colleagues (1990) investigated the methods recommended in the nursing literature for predicting correct placement length for NG/OG tube insertion, including NEX, NEMU, and regression on height.
In a sample of 500 children,
they found regression on height in three age groups to be the superior
predictor of esophageal length. This method, referred to as the age-related,
height-based method, was supported by Hanson's (1979) study in adults.
Radiography and Tube Insertion
Currently an abdominal radiograph is the only consistently valid and reliable way to verify the position of flexible small-bore NG/ OG tubes.
Indeed, radiographs
have been recommended by many to determine tube placement in patients; however,
placement must be checked frequently while a tube is in place, and the
summative radiation risk of multiple radiographs as well as their expense makes
the development of adequate bedside placement locating methods imperative.
Methods to Detect Error In Insertion
Several methods of detection have been investigated in adults, including:
(a) aspirating gastric contents and measuring the pH, bilirubin, pepsin, and trypsin levels.
(b) placing the proximal end of the tube under water and observing for bubbles in synchrony with expirations.
(c) auscultating for a gurgling sound over the epigastrium or left upper quadrant of the abdomen.
(d) examining the visual characteristics of aspirates.
(e) measuring the length from the nose/mouth to the proximal end of the tube.
(f) measuring CO, level at the proximal end of the NG/OG tube.
Each of these methods has its problems, however. Metheny, Smith, and Stewart (2000) found that the combination of pH, bilirubin, pepsin, and trypsin correctly classified 100% of respiratory placements and 93.4% of Gl placements in adults; however, no bedside tests are currently available for measuring pepsin and trypsin, thus limiting their clinical usefulness.
Placing the proximal end of the tube under water and observing for bubbles in synchrony with expirations involves risk that clients will aspirate water on inspiration, especially those being mechanically ventilated, simple auscultation is not a reliable method to assess tube position because injection of air into the tracheobronchial tree or into the pleural space can produce a sound indistinguishable from that produced by injecting air into the GI tract (Metheny, McSweeney, Wehrle , & Wiersema, 1990).
Metheny, Reed, Berglund, and Wehrle (1994) showed that visual characteristics improved nurses' predictions of stomach and intestinal placements but reduced discrimination of respiratory placements.
Finally, there
is evidence that CO, monitoring has the potential to differentiate respiratory
from Gl placement; however, it has yet to be used. Clinically to detect
respiratory placements (Burns, SM, Carpenter, & Truitt, 2001; Thomas, BW,
& Falcone, 1998). To summarize, in adults' pH and bilirubin of aspirate are
the only reliable indicators of tube position.
Fluids Aspiration and Composition
Fluids aspirated from different organs have different mean pH values, and Metheny, Stewart, and coresearchers (1999) suggested that these expected differences might be useful for testing for feeding tube placement errors.
Although an advance over auscultation, pH testing alone is an inadequate locator in both adults and children because of overlap in pH between sites, difficulty in obtaining aspirate, and other factors affecting pH readings.
In a study of 800 aspirates collected from 605 fasting adults, Metheny and coresearchers (1999) found that gastric aspirates had significantly lower pH values (mean 3.5) than intestinal aspirates (mean 7.0).
About 15% of the gastric aspirates had pH values overlapping with the pH values of intestinal aspirates. In addition, pH values from four tubes inadvertently placed in the respiratory tract overlapped with the range in intestinal plaque elements. Although in the research setting investigators were very successful in obtaining as-pirate, in the clinical setting this may be more of a problem.
It may be impossible to obtain any fluid if one or more of the orifices are not in a pool of fluid. Furthermore, flexible small-bore tubes tend to collapse when negative pressure is applied with a syringe; therefore, the absence of fluid is not necessarily evidence of improper placement.
Another factor that may reduce the usefulness of pH testing is the administration of gastric acid-inhibiting medications resulting in an elevated gastric pH, although the evidence is mixed on this question (Metheny et al., 1993; Metheny, Eikov , Rountree, & Lengettie , 1999).
Metheny, Smith, and Stewart (2000) recommended that the bilirubin level and pH of aspirates be jointly used as tests to help differentiate gastric, intestinal, and respiratory placement of tubes.
They measured bilirubin and pH of aspirates from NG and NI tubes as well as tracheobronchial suction and pleural fluid aspirates and found bilirubin. levels to differ as predicted. Metheny and Stewart (2002) found bilirubin levels in neonates' gastric fluid comparable to adult levels.
Although the pH/bilirubin test correctly identified 100% of actual respiratory aspirates, it correctly identified only 85.9% of non respiratory aspirates. Furthermore, only 29.4% of predicted respiratory aspirates were actually respiratory, and 87.7% of non-respiratory placements were accurately predicted.
Metheny and Stewart concluded that a bilirubin concentration of 25 mg/dL was a good predictor of intestinal tube placement, where as a bilirubin concentration of < 5 mg/dl was a good predictor of gastric tube placement whether or not the adult was fasting.
Bilirubin can be
easily measured at the bedside using the method developed by Metheny and
Stewart in which reagent strips are compared to a color scale.
Key Points
In summary, although estimates of tube placement errors vary, there is no doubt that they are common and can lead to serious complications. The direct NEX distance, the standard measurement currently used in practice, has been seen to be inaccurate in both adults and children.
The NEMU distance, tested only in children, also seems to be inaccurate. Although the age related heightbased method has some research support, it has never been tested clinically.
Because of the overlap in pH values for respiratory, gastric, and intestinal placements; the difficulty in obtaining aspirate to test pH; and the possible effects of acid inhibiting medications, total parental nutrition, and physiologic immaturity in young infants on the pH of aspirate.
It is evident
that pH alone is not a reliable method for discriminating among gastric,
intestinal, and respiratory placements. Furthermore, these problems may be
worse in children than adults. Joint measurement of bilirubin and pH may be a better
alternative to the use of pH alone.
Give your opinion if have any.