Unlocking the MIC-KEY: Understanding and Troubleshooting Low-Profile Gastrostomy Tubes

You are working an overnight clinical shift at your community emergency department when a worried mother brings in her 15-year-old child with cerebral palsy due to their gastric tube “coming out.” As you begin to obtain a history of the patient’s gastric tube (when it was placed, where it was placed, why is it in place, etc.) you realize you will be the one replacing it tonight, and frankly you haven’t done this before. The following post serves as a refresher on the use, placement, and complications of gastrostomy tubes.

Gastrostomy Basics

Gastrostomy tubes, commonly referred to as G-tubes, GJ-tubes, PEG tubes, or low-profile gastrostomy tubes (“MIC-KEYs”) are devices used for enteral access that are placed into the stomach through the abdominal wall. The distal end of gastrostomy tubes can end in the stomach (“G-Tube”) or be threaded past the pylorus into the jejunum (“GJ Tube”). These are unique from jejunostomy tubes (“J-Tube”), which are passed directly percutaneously into the jejunum. GJ-tubes and J-tubes cannot be replaced at the bedside and require endoscopic or fluoroscopic replacement. Most G-tubes have 2 external ports with separate functions (image 1):

1. Insufflation of the retention balloon
2. Administration of medication and/or nutrition into the stomach (image 1)

Some G-tube models have additional ports dedicated to gastric decompression or for simultaneous administration through two different ports (ie: medications and feeds at the same time).

A GJ-tube has an additional port for jejunal access. The gastric port in GJ-tubes is generally used for medications (for adequate absorption via the stomach mucosa) and decompressing the stomach while the jejunal port is used for nutritional feeds. A GJ-tube or J-tube is preferred in patients who are at high risk for aspiration, as feedings through the jejunal port are less likely to be regurgitated backward past the pylorus [1]. G-tubes may sometimes have a “mushroom” end for retention that does not have a balloon that requires inflation- these are often used during initial placement (Image 1) [1,2].

Gastrostomy tubes can be placed endoscopically, surgically, or under fluoroscopic guidance. Endoscopic placement is most common and involves simultaneous endoscopy of the stomach and external placement of the tube [3].

The endoscope is used to evaluate the stomach lining and determine if the desired placement site is free of ulcers or local inflammation. A needle is externally placed into the abdominal wall and is verified via endoscopy to be in the correct location followed by percutaneous placement of the G-tube.

“PEG Tube” vs. “MIC-KEY button” 

A PEG tube commonly refers to all G/GJ-tubes regardless of placement technique. PEG tubes have long tubing and are often the device used for initial placement. A MIC-KEY, a trademarked name, commonly refers to a lower profile gastric tubes (or “button,” (Image 2)) that sits at the level of the skin. Instead of the longer tube seen in PEG tubes, low-profile buttons come with an extension set that is attached for feeding (Image 3) and can be disconnected for comfort in between feeds.

Low-profile buttons are preferred in pediatric patients who are at higher risk of accidentally dislodging their tube or pulling on longer tubing. Low-profile tubes are sized based on the stem length and caliber of the access tube (Image 4). The tract of the gastrostomy usually matures 1-2 weeks after initial placement but can take up to 3-4 weeks before it is considered safe to replace without real-time fluoroscopic guidance [1,2].

Troubleshooting Low-profile Gastrostomy Tubes  

Replacing the device

Before an EM provider decides to replace a low-profile button, they should:

• Ensure the gastrostomy track is mature (timeline mentioned above) and that the replacement button is intact and the correct size.
• Ensure that the new button’s port flushes and that the balloon is intact by inflating and deflating it prior to placement while checking for signs of leakage.
• Balloons should be filled with the appropriate volume of sterile water noted on the package insert for that size (usually 3-5 mL for buttons, Image 5).
• Avoid saline solution as solute may precipitate over time and prevent the balloon from eventually being decompressed (similar to urinary catheters).

Children with PEG tubes and buttons often have multiple chronic issues that require frequent medication and nutrition administration and are prone to electrolyte abnormalities.

• If an EM provider is concerned that replacing a gastrostomy tube will take time, alternative access (nasogastric tubes or IV access) should be considered in the interim.
• Some children may require mild sedation. Excessive crying/screaming causes tensing of the abdominal wall, making passage of the gastrostomy tube more difficult.
• Ample water-based lubricant should be used when replacing gastrostomy tubes through a mature tract.
• Having problems maintaining tube stiffness during placement? Consider using a Q-Tip or pediatric ETT stylet to help direct the tube through the gastrostomy while ensuring not to cause damage with the distal end.
• If the gastrostomy is too tight to pass, consider using urinary catheters if available.

If unable to replace the original gastric tube:

• An improvised feeding tube can be kept in place to administer medications and feeds until an appropriate replacement piece can be found [1].
• The urinary catheter should be anchored in place (consider a modified external stopper, abdominal binder, or another improvised mechanism).

Confirming Placement:

• Confirm placement by instilling 10-20mL of water-soluble contrast (eg. Gastrograffin) via the new device followed immediately by an upright abdominal radiograph, especially if there are difficulties or concerns with placement [1].
• If there are signs of intraperitoneal contrast extravasation, EM providers should seek expert consultation to manage complications and eventual replacement [1].
• Complications may include peritonitis, fistula, bleed, or need for surgical repair [3].

Managing Complications

Redness

Some local erythema is a normal side effect of external skin exposure to gastric contents. However, if a patient or caregiver notices worsening or expanding erythema with local tenderness this may be secondary to various causes:

• Loose gastrostomy tubes:  This can be caused by balloon leak/low volume, a loose external bumper, or significant weight loss. Check balloon integrity, external bumper placement (position should be marked on external tubing), and proper size.
• Infection: Consider local treatment with topical anti-fungal or oral antibiotics.
• Irritation from gastric acids: Consider the use of topical antacids such as Carafate and barrier creams containing zinc oxide as prophylaxis [3,4].
• Bleeding: This is not uncommon and usually secondary to the formation of granulation tissue [3]. Small, persistent bleeds that do not improve with direct pressure can be stymied with judicious application of silver nitrate.

Pain

Often caused by a tight G-tube of button. Evaluate for the following:

• Overinflation of the external bumper.
• Improper sizing due to weight gain.
• A phenomenon called “buried bumper syndrome”, in which the bumper is inadvertently pulled into the track [5].
• Also consider site infection, gastrointestinal bleeding, ulcers, herniation at ostomy site, volvulus, and dislodgement.

Nausea/Emesis

A common side effect that can highlight underlying issues:

• High residuals (>100 mL) in patients with constipation, gastroparesis, or when nutritional feeds are being given too often or in higher volumes.
• Gastric outlet obstruction caused by over-inflated balloons or balloons that have migrated distally from gastrostomy [3].
• Check the residual volumes since last feed and consider removing/replacing the gastrostomy tube with appropriate size/placement.

Unable to Remove Gastrostomy Tube

This may be from a balloon that cannot be deflated. Consider trying to deflate the balloon using an IV catheter. Providers may consider puncturing the balloon with a guidewire (from a central venous access or arterial line kit) via the inflation port. Expert consultation should be considered if ultimately unable to remove.

Clogged Port

This can be prevented by ensuring ports are being flushed and medications/feeds are being administered through proper ports. To treat:

• Pressure-flushing the G-tube or button with warm water has shown some success. Be careful not to damage tubing [1, 3].
• Several chemical disimpaction solutions exist (cola, pancrealipase, and commercial solutions like Clog Zapper) and have mixed success as well [3].
• Mechanical devices similar to plastic pipe-cleaners exist and are preferred over wires/needles that increase the risk of causing perforation.
• Have a low threshold to replace the device if unable to successfully unclog or get adequate flow.

Electrolyte Abnormalities

Patients, especially children, that are dependent on G-tubes are often prone to multiple electrolyte abnormalities.

• Consider monitoring serial serum glucose and consider giving dextrose-containing maintenance IV fluids if a patient is not receiving consistent feeds during the replacement process.
• Patients that require free-water are prone to hyper- and hyponatremia depending on the amount and frequency of flushes.
• Calculating free-water deficit and watching for symptoms of severe hyponatremia and hypernatremia are key in these patients.

References

1. Samuels, LE. Nasogastric and Feeding Tube Placement. In: Roberts J, ed. Roberts and Hedges’ Clinical Procedures in Emergency Medicine and Acute Care, 7th ed. Philadelphia, PA: Elsevier. 2019:693-718.
2. Juern J, Verhaalen A. Gastromy-tube Exchange. N Engl J Med. 2014;370: e28. PMID: 24785226.
3. Schrag SP, Sharma R, Jaik NP, et al. Complications related to percutaneous endoscopic gastrostomy (PEG) tubes. A comprehensive clinical review. J Gastrointestin Liver Dis. 2007;16(4):407-18. PMID: 18193123.
4. Hayashi AH, Lau HYC, Gillis DA. Topical Sucralfate: Effective therapy for the management of resistant peristomal and perineal excoriation. J Pediatr Surg. 1991;26(11): 1279-1281. PMID: 1812256.
5. Cyrany J, Rejchrt S, Kopacova M, Bures J. Buried bumper syndrome: A complication of percutaneous endoscopic gastrostomy. World J Gastroeneterol. 2016; 22(2): 618-627. PMID: 26811611.

 

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