Research Applied to Clinical Practice
by Robert C. Knies, RN MSN CEN
Section Editor
Confirming Safe Placement of Nasogastric Tubes
The purpose of confirming the placement of the NGT after inserting is to prevent the high-risk complications that can occur including, pulmonary hemorrhage, empyema, esophageal perforation, pneumothorax, pleural effusion, and pneumonitis (Fater, 1995). Most nursing textbooks describe NGT insertion as a nursing procedure, however, these same textbooks ignore discussions on research related to insertion and avoid discussion on NGT removal (Schmieding, Waldman, & DeSaulles, 1997).
Several popular nursing textbooks (Black & Matassarin-Jacobs, 1993; Craven & Hirnle, 1992; Monahan, Drake, & Neighbors, 1994) list air insufflation and auscultation as the accepted method for checking placement. Monahan et al. (1994) suggested immersing the end of the tube in water to check for bubbling. Ignatavicius, et al., (1995) lists aspirating, and checking the pH of the aspirate or confirming by x-ray as the only acceptable methods of checking placement.
Metheny and colleagues have done numerous studies on the common, established practices of confirming NGT placement, in an attempt to prove effectiveness. Those practices include, air insufflation and auscultation, aspiration of gastric fluid, ability of the patient to phonate, and assessment/observation of the visual characteristics of the aspirate. Metheny, et al., (1988), performed a series of studies and found that nurses listening to the sounds of insufflated air over the epigastrium were unable to differentiate NGT placement between the stomach and the esophagus or small intestine. In 1990, Metheny, Dettenmeier, et al., performed a similar study and proved that nurses could not differentiate between the stomach and the respiratory tract. In 1994, Metheny, Reed, Berglund, & Wehrle, evaluated the effectiveness of assessment and visualization of the aspirate. Results from all of these studies indicate that radiographic determination of placement is the most accurate. However, this author recognizes that this method is impractical in emergency situations and very costly for non-emergency situations.
In 1994, Metheny and her colleagues found that, of the simple bedside measures to determine NGT placement that are both simple, accurate and economical, the best is a combination of measuring pH and visual characteristics. This group also suggested a process that adds measurement of bilirubin and enzyme content of the aspirate (Schmieding, Waldman, & DeSaulles, 1997).
Testing the pH of the aspirate while not 100% reliable is more accurate than other non-radiologic methods. However, this method is not without its own problems. Several treatments and disease processes can affect the pH concentrations. For example, last intake of fluids, the type of fluid, feeding formulas and medications will alter the pH. Patients taking H2 receptor blockers and those with illnesses such as, HIV, pernicious anemia, and GERD will have higher pH concentrations (Metheny, Reed, Wiersma, et al., 1993).
There is another important process change concerning the pH methods for confirming placement in relation to continuous tube feedings. To promote accuracy, the feedings must be stopped one hour prior to obtaining aspirate (Fater, 1995). This action promotes the normal gastric emptying, however, it will affect the total caloric intake if the rates of infusion are not adjusted after this delay. It may affect the total intake also if the volume must be increased to makeup for the time loss. Another issue is the competency and quality control components of the pH testing, which can be done on the Gastrocult™ cards.
So, what does this mean clinically? Clearly there is a need for nursing practice to be consistent with the research findings. Therefore the CNS group will be the process owners of this change. Until we -roll out- this change, you can use the following information and apply the practice today!
Normal gastric aspirate color is clear to slightly yellow. If patient is a GI bleed or obstructed, there will naturally be different colors. Normal pH is from 1 to 4, it is higher if in the small intestine and even higher if in the lungs. If you insert an NGT and cannot get an aspirate sample, consider pulling the tube 1 to 1 1/2 inches in or out and try again. If the patient has an altered level of consciousness, is restless, or requires constant tube feedings or frequent endotracheal suctioning, then he should have placement confirmed radiographically.
References:
Fater, K.H. (1995). Determining nasoenteral feeding tube placement. MedSurg
Nursing, 4(1), 27-32.
Metheny, N. (1988). Measures to test the placement of nasogastric tubes and nasointestinal
feeding tubes: A review. Nursing Research, 37 (6), 324-329.
Metheny, N., Dettenmeier, P., Hampton, K., Wierman, L. & Williams, P. (1990).
Detection of inadvertent respiratory placement of small-bore feeding tubes: A report of 10
cases. Heart and Lung, 19 (6), 631-638.
Metheny, N., Reed, L., Berglund, B., & Wehrle, M. (1994). Visual characteristics of
aspirates from feeding tubes as a method for predicting tube location. Nursing Research,
43(5), 282-287.
Metheny, N., Reed, L., Wiersma, L., McSweeny, M., Wehrle, M.A., & Clark, J.
(1993). Effectiveness of pH measurements in predicting feeding tube placement: An update.
Nursing
Research, 42 (6), 325-331.
Schmieding, N.J., Waldman, R.C., DeSaulles, C. (1997). Nasogastric tubes: Insertion,
placement and removal in adult patients. Gastroenterology Nursing, 20(1), 15-19.
"Research Applied to Clinical Practice: Confirming Safe Placement of
Nasogastric Tubes"
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is a webarticle by Robert C.
Knies, RN MSN CEN [bknies@stevenshealthcare.org]
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