Confirming Gastric Tube Placement: What’s New?

 

There has been, and remains to be, much discussion (and a little practice change) about confirmation of gastric tube placement. While this doesn’t seem like such an “intensive care” activity, it is certainly high risk.

Current gastric tube placement methods

Babies who are doing well growing and getting feedings via a gastric tube can quickly end up back in the ICU or worse if the tube becomes displaced. There are several methods that have been used for gastric tube placement including:

• Auscultation
• Aspiration of fluid
• pH testing
• Ultrasound
• Radiologic verification

It is recognized that auscultation is probably the least accurate method of determining placement because the audible sound of air entering the stomach cannot be distinguished from air entering the lung should the tube be misplaced into the trachea. Various sources now recommend against use of the auscultation method.

Radiologic verification remains the gold standard, but is impractical for every gastric tube placement in neonates. A recent integrative review found studies looking at the following for purpose of determining tube position:1

• gastric secretion aspiration
• epigastric region auscultation
• checking aspirated secretion’s pH, pepsin, trypsin and bilirubin
• secretion color
• presence of CO2 test
• acid test with litmus paper
• reading diaphragm’s electrical activity
• electromagnetic tracing
• use of indigo carmine at 0.01%

These review authors concluded that the two top indicators of either correct tube placement (color of secretions and pH testing) or incorrect placement (lack of ability to aspirate fluid and pH testing) were secretion or pH related.

The same study that evaluated pepsin, trypsin and bilirubin in the secretions also used aspirated secretions and pH to evaluate correct placement of the tube.2 The use of pH testing to verify tube placement has become more popular.  Two studies evaluated the pH that would represent gastric secretions in the neonate.3, 4

Meert et al compared pH testing in infants who were NPO with and without the use of acid inhibitors and infants who were receiving feedings with and without gastric acid inhibitors.3 Gastric and duodenal aspirates were taken, and 67 – 97% had a gastric pH of less than 5.5 regardless of whether they were being fed or receiving gastric acid inhibitors. Tracheal aspirates are often at or above a pH of 6.0.  Therefore, these authors conclude that a pH of less than 5.5 should be safe in determining gastric placement of the tube, although it does not rule out duodenal placement.3

Some of these same researchers evaluated various pH cut points and published results in 2017.4 In that study, they found the best positive predictive value to be a pH of less than 5.0. So, a pH of less than 5.0 would be most accurate in showing the tube is in the correct position.

The study also evaluated the use of a pepsin assay in predicting proper tube placement.4 Pepsin levels are much higher in gastric aspirate than tracheal aspirate but, unfortunately, are not practical for bedside use. The researchers reported that the test takes about 15 minutes to complete on a countertop.4 Fifteen minutes to check tube placement is not practical, and would be only one required measure. It is suggested as a secondary test after pH, for example.

The integrative review reinforces what has been known for some time now about using auscultation as a method to confirm tube placement.1 It is not accurate and should be abandoned. Some have noted that auscultation along with gastric secretion aspiration is more accurate than either alone, but this review did not find agreement on that.

The acid test with litmus paper5 simply shows whether the secretions are acidic or alkaline, but does not provide the specific numbers that pH testing provides. Therefore, it may be helpful as a quick test – but is not very accurate.

Technology and gastric tube placement

Two more high tech methods of determining tube placement include reading the diaphragm’s electrical activity, and electromagnetic tracing.

The first device is a catheter or tube embedded with an electrical device that senses diaphragmatic movement during tube insertion.6 While this study only included 20 children, all tubes were placed correctly as evaluated by x-ray reading. However, it requires the use of a specific, expensive tube and as such, remains impractical for routine use.

The use of an electromagnetic tracing device allows for correct placement or redirection of the tube.7  This device reportedly resulted in 100% correct placement by the second attempt, and avoidance of incorrect placement in four pediatric patients. The study included patients from newborn to 102 years of age, with a small number of pediatric patients and an even smaller number of neonates. Furthermore, special training is required to be able to interpret the electromagnetic device readings.7  Not that nurses couldn’t be taught to read those results, but perhaps it’s not the most practical solution.

Indigo carmine for placement

Another interesting and unusual method for checking accurate placement is the “sky blue” method, or use of indigo carmine.8 That study included newborns only, and involved a gastric tube “exchange.” The indigo carmine was placed through the tube that was confirmed radiologically, and without removing that tube, another tube was placed. Once believed to be in the appropriate position, confirmation was the aspiration of a sky blue gastric aspirate, indigo carmine.  This was determined to be more accurate as an indication of proper placement if the new tube was placed anterior to the old tube.  This study reported that 94.4% of the tubes placed produced a blue aspirate. A weakness of the study is that long term effect of indigo carmine is not known, and tube exchanges done in that manner may not be as practical in very low birth weight infants.

In conclusion

While there are some nifty things being evaluated to test for proper tube placement, they aren’t cost effective and/or useful clinically yet. However, we have enough information to use pH testing on a more routine basis, along with aspiration of gastric aspirate.

The most common reason for not getting an aspirate from a tube is that it is up against the stomach wall. Repositioning the infant and the tube may be helpful in obtaining an aspirate. Obviously, pH testing cannot be done without the aspirate, so both are necessary, and the presence of aspirate serves to validate proper placement as well. If gastric aspirate cannot be obtained, even after repositioning the tube and/or the infant, that is also a fairly reliable indication of improper placement.1

Tell us more in the comments below! How does your NICU currently confirm gastric tube placement?

 

Looking for more on this topic? Read Complications of Neonatal Gavage Tubes.

 

References:

1. Dias FD, Emidio SC, Lopes MH, Shimo AK, Beck AR, Carmona EV. Procedures for measuring and verifying gastric tube placement in newborns: an integrative review. Revista latino-americana de enfermagem. 2017;25.
2. Metheny NA, Eikov R, Rountree V, Lengettie E. Clinical research: indicators of feeding-tube placement in neonates. Nutrition in Clinical Practice. 1999 Dec;14(6):307-14.
3. Meert KL, Caverly M, Kelm LM, Metheny NA. The pH of feeding tube aspirates from critically ill infants. American Journal of Critical Care. 2015 Sep 1;24(5):e72-7.
4. Metheny NA, Pawluszka A, Lulic M, Hinyard LJ, Meert KL. Testing Placement of Gastric Feeding Tubes in Infants. American Journal of Critical Care. 2017 Nov 1;26(6):466-73.
5. Nyqvist KH, Sorell A, Ewald U. Litmus tests for verification of feeding tube location in infants: evaluation of their clinical use. Journal of clinical nursing. 2005 Apr 1;14(4):486-95.
6. Green ML, Walsh BK, Wolf GK, Arnold JH. Electrocardiographic guidance for the placement of gastric feeding tubes: a pediatric case series. Respiratory care. 2011 Apr 1;56(4):467-71.
7. Powers J, Luebbehusen M, Spitzer T, Coddington A, Beeson T, Brown J, Jones D. Verification of an electromagnetic placement device compared with abdominal radiograph to predict accuracy of feeding tube placement. Journal of Parenteral and Enteral Nutrition. 2011 Jul;35(4):535-9.
8. Imamura T, Maeda H, Kinoshita H, Shibukawa Y, Suda K, Fukuda Y, Goto A, Nagasawa K. Confirmation of Gastric Tube Bedside Placement With the Sky Blue Method. Nutrition in Clinical Practice. 2014 Feb;29(1):125-30.