So what’s the big deal about inserting an NG tube? That’s a question we heard recently at a hospital. The questioner thought the answer would be simple. It’s not. Nasogastric tube (NG tube) insertion is so common that we tend to forget its risks. But if you’ve ever seen a patient die because their enteral feeds were inadvertently given into their lungs or develop meningitis because the NG tube went through a basal skull fracture, you won’t take this cavalier attitude toward NG tubes.
Indeed, the UK’s NPSA issued 2 Patient Safety Alerts in 2005 (NPSA 2005a, NPSA 2005b) because of numerous reports of incidents and bad outcomes related to NG tubes. And because they have had 21 deaths and 79 cases of harm due to feeding into the lungs through misplaced NG tubes since that original alert, the NPSA reissued the alert in March 2011 (NPSA 2011). In 45 of the 79 cases of harm (and 12 of the deaths) the primary contributing factor was misinterpretation of x-rays.
The 2005 alert noted that while the most accurate method for confirming correct tube placement is radiography, there had been multiple reports of x-rays being misinterpreted by physicians not trained in radiology. Other problems noted with radiographic confirmation included increased exposure to radiation, loss of feeding time and increased handling of seriously ill patients. Plus, outside of the acute care setting, access to radiology is often difficult. Therefore, the recommendation in the UK was that radiography should not be used ‘routinely’ for verification of tube placement and that the first line test to be used is determination of pH of the aspirate.
However, pH testing of the aspirate has its own limitations. A number of medications, such as proton pump inhibitors or H2 antagonists or antacids may affect the pH of gastric fluid. Secondly, the feeds themselves may affect pH of the fluid and it may even be difficult to obtain fluid on aspiration. In addition, the correct type of litmus testing paper must be used.
Just as importantly, they noted several other methods that should not be used for determining tube position. The “whoosh” test (auscultation while air is injected into the tube) is notoriously unreliable. Similarly, looking for air bubbles in the tube is also unreliable since air may be present in the stomach as well as the lungs. And simply observing the patient for respiratory distress is not reliable.
The new alert starts with some good common sense recommendations. First, before inserting an NG tube there should be an assessment as to whether NG feeding is appropriate for the patient and the rationale for that decision should be documented in the chart. Second, placement of the NG tube should be delayed (unless urgent) if there is not appropriate skill and expertise available to confirm tube placement (for example, at night). Third, the NG tube to be inserted should be radio-opaque throughout its length and have externally visible external length markings. Fourth, no feeds or flushing of the tube should take place until position is confirmed either by pH testing or x-ray.
They continue to recommend pH testing as their first line method, with a “safe” pH being between 1 and 5.5. They recommend x-ray confirmation when there is no aspirate or the pH is not in the target range.
When radiographic confirmation is needed they also have practical advice. First, the x-ray requisition should clearly state the x-ray is for determination of tube placement. All too often we still see x-ray requisitions filled out with something like the admission diagnosis rather than the real reason for the x-ray. And you need to make sure that the person doing the interpretation is appropriately credentialed to do so (for example, if someone other than the radiologist is doing the interpretation).
They provide some examples of radiographs prone to misinterpretation. One seems to show the tip of the catheter below the left hemidiaphragm but it is actually in the left lower lobe of the lung. Another shows the difficulty of determining tube position when artifacts, such as those do to EKG leads, are present. And they describe the responsibilities of both the radiology tech and the radiologist in the process. The former must ensure correct film exposure and that the bottom of the hemidiaphragms are adequately seen. The radiologist is responsible for documenting the position of the tube and its tip and noting whether it is safe to proceed with feedings.
The alert goes on to discuss repeat checks after the correct position has been initially confirmed. It’s recommended position be rechecked before each feed, any time medication is to be given via the tube, and at least daily. Also, any time there is reason to believe the tube may have been misplaced (eg. after movement, retching, coughing, unexplained respiratory symptoms, etc.) position should be rechecked. The alert discusses how to appropriately assess for displacement also by visualizing the length markers.
Lastly, they recommend a full multidisciplinary assessment be done before a patient with an NG tube is discharged from acute care to other settings.
Another paper (Eveleigh 2011) describes a case of a patient in whom feeds were given via NG tube that was positioned in the lungs and the subsequent root cause analysis. The x-ray was misinterpreted in the middle of the night by a junior physician who had inadequate training in interpretation for NG tube placement. So the organization did a further audit on cases and found that there were 43 errors in interpretation of tube position in 192 position placement x-rays. Moreover, documentation of the interpretation was missing in 41% of the charts. Moreover, the mean time from ordering the x-ray to time actually performed was 4 hours.
Actions taken as a result of the RCA included a new educational/competency assessment program for all junior physicians, development of a standardized NG feeding tube care plan, avoiding placing NG tubes out-of-hours unless critical, re-prioritization of these cases in the radiology department, a standardized NG tube insertion sticker for documentation purposes, and switch to one standard NG tube type. In one year, they reduced the number of misinterpreted studies to one, cut the x-ray delay time in half, and significantly improved chart documentation.
There is also an excellent e-learning tool on the Merck Serono web site for interpreting x-rays for placement of NG tubes, including a nice flow chart of the questions to ask when viewing such radiographs. The module includes a case description of a patient inadvertently fed through a misplaced feeding tube and summarizes results of an RCA that identified root causes in the following areas: human factors, equipment factors, system factors, environmental factors, and communication factors. Identification of anatomical landmarks and taking into account rotational factors were stressed in x-ray interpretation. They provide some good sample x-rays to see correct and incorrect positioning.
The first line study in most US hospitals remains radiologic confirmation. In the US, radiologists are available more frequently. Even in those facilities where a radiologist is not present on site, they are often able to interpret films remotely via teleradiology. However, that does not mean you can’t learn a lot from the above alerts and RCA’s. We’re willing to be that if you do an audit you’ll find considerable deficiencies in documentation of tube positioning before feedings are started. Particularly if you have physicians other than radiologists confirming the NG tube position (eg. at night) you want to make sure they have had the appropriate training and competencies to do so. And if you are having radiologists read the films remotely via teleradiology at night, take a hard look at the documentation of tube position, how that result gets communicated to everyone who needs to know, and how long it takes.
There are many other facets of NG feeding that we have not covered here. For example, the common practice of grinding up oral medications and giving them via NG tube may be dangerous in certain cases. The recently approved oral anticoagulant, dabigatran, may result in toxic levels if given that way. So there are a whole host of other patient safety issues surrounding NG feeding well beyond those related just to position.
So what’s the big deal about inserting an NG tube? It’s a lot bigger than you thought!
National Patient Safety Agency (UK). Patient Safety Alert. Reducing harm caused by the misplacement of nasogastric feeding tubes. February 21, 2005
National Patient Safety Agency (UK). Patient Safety Alert. Reducing the harm caused by misplaced naso and orogastric feeding tubes in babies under the care of neonatal units. September 18, 2005
National Patient Safety Agency (UK). Patient Safety Alert. Reducing the harm caused by misplaced nasogastric feeding tubes in adults, children and infants. March 10, 2011
the supporting information
the decision tree for adults
the decision tree for children and infants
Eveleigh M, Law R, Pullyblank A, Bennett J. Nasogastric feeding tube placement: changing culture. NursingTimes.net October 17, 2011
Merck Serono. Reducing the fisk of feeding through a misplaced nasogastric tube. E-Learning module. March 2011
flow diagram for interpreting x-rays for tube placement