Nasogastric Tube

Anatomy and Physiology

The nares are the anterior opening of the nasal sinuses. 5 to 7 cm posterior to the nares, the nasal sinus connects to the nasopharynx, which is continuous with the oropharynx. The pharynx's length from the skull's base to the esophagus's start is 12 to 14 cm. The esophagus starts at the upper esophageal sphincter, the cricopharyngeus, and runs down through the diaphragm to the stomach for a length of approximately 25 cm. While the stomach is a highly distensible structure and, therefore, can vary in length, the empty stomach is generally around 25 cm long. Thus, if one intended to place a tube through the nares and place it in the middle of the stomach, approximately 55 cm of the tube should be inserted.[3]

Several methods estimate the depth at which an NG should be placed. All estimation methods have some margin of error.[4] A common pre-procedure maneuver is to loop the tube over 1 of the patient’s ears, place the tip at the patient’s xiphoid process, and estimate the length of the tube that should be inserted.[5]

Indications

The most common indication for placing a nasogastric tube is to decompress the stomach in the setting of distal obstruction. Small bowel obstruction from adhesions or hernias, ileus, obstructing neoplasms, volvulus, intussusception, and many other causes may block the normal passage of bodily fluids such as salivary, gastric, hepatobiliary, and enteric secretions.[2] These fluids build up, causing abdominal distension, pain, and nausea. Eventually, the fluids build up enough that nausea progresses to emesis, putting the patient at risk for aspiration, an event with mortality as high as 70% depending on the volume of fluid aspirated. Similarly, intractable nausea or emesis, whether caused by medications, intoxication, or other reasons, can be an indication for the placement of a nasogastric tube to prevent aspiration. Prophylactic placement of NG tubes in patients with abdominal surgery is not recommended. Patients who develop postoperative ileus tend to recover faster without the placement of an NG tube.[6]

Less commonly, nasogastric tubes can be placed to administer medications or nutrition in patients with a functional gastrointestinal tract but cannot tolerate oral intake. This is most common in patients who have suffered a stroke or other malady which has left them unable to swallow effectively.[3] Nasogastric tubes may be placed for nutritional support while waiting to see how much function the patient recovers. Suppose the patient does not recover their swallowing ability or otherwise requires long-term nutritional support. In that case, a more permanent feeding tube, such as a gastrostomy or jejunostomy feeding tube, should be placed.

NG tubes have been used for various reasons in patients with GI bleeding. In the past, NG lavage was thought to help control GI bleeding. However, recent studies have shown that this is not helpful.[7] Another indication for the placement of a nasogastric tube is in the setting of massive hematochezia. Given that an upper GI bleed causes up to 15% of massive hematochezia, placement of a nasogastric tube after initiating resuscitation may potentially aid in diagnosis. Of note, an upper GI source of bleeding is only ruled out after aspiration of gastric contents from a nasogastric tube if the fluid is bile-tinged. If the fluid is not bile-tinged, it is possible that a duodenal ulcer has caused bleeding but also scarred the pylorus, causing a gastric outlet obstruction, which prevents the blood from aspirating from the stomach.[8] However, the placement of an NG tube has not been shown to improve patient outcomes in patients with GI bleed.[9]

Contraindications

The most common contraindication to the placement of nasogastric tubes is if there is significant facial trauma or basilar skull fractures. In these cases, attempted placement of a tube via the nares may exacerbate the existing trauma. In rare cases, nasogastric tubes have even been placed into the skull in the setting of basilar skull fractures.[10] Esophageal trauma is also a potential contraindication, especially in the setting of ingestion of caustic substances, where the placement of a nasogastric tube may create or worsen perforations. Esophageal obstruction, such as with a neoplasm or foreign object, is an obvious contraindication to nasogastric tube placement. Anticoagulation is a relative contraindication as the trauma from tube placement may cause bleeding. For patients with previous gastric bypass surgery, hiatal hernia repair, or abnormal GI anatomy, NG tubes should be placed under endoscopy.[11]

Equipment

Since there are several nasogastric tube types, selecting the correct tube is the most important part of gathering equipment. For decompression, the standard tube used is a double-lumen nasogastric tube. There is a double-one large lumen for suction and 1 smaller lumen to act as a sump. A sump allows air to enter so the suction lumen does not become adherent to the gastric wall or obstructed when the stomach fully collapses.

If the tube is being placed for administering medications or nutrition, then a small-bore single-lumen tube such as a Dobhoff or Levin tube may be placed. A Levin tube is just a simple small-diameter tube. A Dobhoff is a small-diameter tube with a weight on the end. The weight is added in hopes that gravity and peristalsis advance the end of the tube past the pylorus, given an additional barrier between the nutrition or medications administered and any potential aspiration risk.

Additional essential equipment is some type of sterile lubricating gel to dip the tube into to ease its passage through the sinus cavity, as well as gloves to protect the patient and whoever is placing the tube. The gloves do not have to be sterile, as this is a nonsterile procedure.

Non-essential, helpful equipment is a cup of water with a straw in it for the patient to sip from during the procedure, provided they can tolerate it. This swallowing action helps advance the tube, and the water can ease some irritation on the back of the oropharynx from the tube. The topical use of local anesthetics such as lidocaine is not very useful.[12][13] However, there is evidence that nebulized lidocaine relieves discomfort and increases the chance of NG tube placement.[14] Having a basin nearby in case the patient has an episode of emesis during the procedure is also advisable.

Personnel

While an experienced provider can place a tube by themselves, having an assistant nearby can be helpful in case extra supplies, such as a basin, need to be obtained during the placement procedure if the patient begins to have emesis.

Preparation

The indication for the procedure, potential complications, and alternative to treatment should be explained to the patient, and an informed consent form should be signed. The patient should be placed in the sitting position if possible. Some sort of protective sheet should be placed on the patient’s chest in case they have an episode of emesis during the procedure. The nasogastric tube should be connected to the suction tubing, and the suction tubing should be connected to a suction bucket before tube placement to minimize the risk of spillage of gastric contents. All supplies should be close at hand to minimize unnecessary movement during the procedure.

Technique or Treatment

The individual placing the tube should put on nonsterile gloves and lubricate the tip of the tube (see Image. Nasogastric tube Tip Encircled). A common error when placing the tube is to direct it upward as it enters the nares; this causes the tube to push against the top of the sinus cavity and cause increased discomfort. The tip should instead be directed parallel to the floor, directly toward the back of the patient's throat. At this time, the patient can be given a cup of water with a straw to sip from to help ease the passage of the tube. The tube should be advanced with firm, constant pressure while the patient sips. If there is a great deal of difficulty in passing the tube, a helpful maneuver is to withdraw the tube and attempt again after a short break in the contralateral nares, as the tube may have become coiled in the oropharynx or nasal sinus. In intubated patients, reverse Sellick's maneuver (pulling the thyroid cartilage up rather than pushing it down during intubation) and freezing the NG tube may help facilitate the tube placement.[15] Once the tube has been inserted appropriately, typically around 55 cm, as previously noted, it should be secured to the patient's nose with tape.[16]

Once the tube has been advanced to the estimated necessary length, the correct location is often made obvious by aspirating a large amount of gastric contents. Pushing 50 cc of air through the tube using a large syringe while auscultating the stomach with a stethoscope is a commonly described maneuver to determine the tube's location, but it is of questionable efficacy.[17][18] Misplaced NG tubes in the left mainstem and small bowel can sound similar to adequately placed NG tubes. Taking an abdominal x-ray is the best way to confirm the location of the tube, even if there is the aspiration of gastric contents, as the tube may be placed past the pylorus where it aspirates not just gastric secretions but also hepatobiliary secretions, leading to persistently high output even when the patient's acute issue has resolved. If feeding is planned through the tube, then it is imperative to confirm its location, as placing feeds into the lungs can cause potentially fatal complications. The ideal location for an NG tube placed for suction is within the stomach because placement past the pylorus can cause damage to the duodenum. The ideal location for an NG feeding tube is postpyloric to decrease the risk of aspiration.

The removal of an NG tube is usually a simple procedure. However, the tube should not be forcefully removed as it can become knotted.[19]

Complications

The most common complications related to the placement of nasogastric tubes are discomfort, sinusitis, or epistaxis, all of which typically resolve spontaneously with the removal of the nasogastric tube. As noted previously in the contraindications, nasogastric tubes may cause or worsen a perforation in the setting of esophageal trauma, particularly after caustic ingestion, where extreme caution must be used if the placement is attempted. Blind placement of the tube in patients with injury to the cribriform plate may lead to intracranial placement of the tube.[20] The intragastric placement must be confirmed if the tube is being placed for administering medications or nutrition. Introducing medication or tube feeds to the lungs can cause major complications, including death.[2] Even in intubated patients, the NG tube can still be accidentally placed into the airway.[21] Another complication that all those managing nasogastric tubes should be aware of is specifically for the double-lumen nasogastric tubes. These large diameter tubes stent the lower and upper esophageal sphincter open while in place. If the tube becomes obstructed or otherwise malfunctions and cannot decompress the stomach, it potentially increases the risk of an aspiration event secondary to this stenting effect.[22] Prolonged use of NG tubes can irritate the gastric lining, causing gi bleeding.[23] Patients with extensive irrigation with an NG tube can develop electrolyte abnormalities such as hypokalemia.[24] Prolonged pressure on 1 area of the nare can cause nasal pressure ulcers or necrosis.[25] The tube should be retaped intermittently to prevent this complication.

Clinical Significance

Whether decompressing the stomach, providing enteral access for nutrition and medications in a patient unable to tolerate them orally, or ruling out an upper GI source of bleeding in the setting of massive hematochezia, nasogastric tubes are part of the standard of care for many routine health issues. Physicians should readily place nasogastric tubes if indicated and should be able to manage them effectively. Given the potential for major complications, particularly if medications or tube feeds are given intrapulmonary, with inappropriate nasogastric tube placement, the entire healthcare team must know the indications, contraindications, possible complications, and appropriate work-up to confirm placement.

Enhancing Healthcare Team Outcomes

As mentioned above, while having at least 1 assistant nearby when placing a nasogastric tube is helpful, an experienced healthcare provider can generally place 1 alone without much difficulty. Interprofessional care comes into play when maintaining nasogastric tubes. Physicians should check that the nasogastric tube is functioning and not clogged or malfunctioning when they round. Clinicians should also routinely inspect their patients' nasogastric tubes to ensure they are functioning and have a high index of suspicion for potential aspiration events. Frequent examinations by all healthcare providers to ensure the tube is securely in place and properly positioned can also reduce injuries associated with nasogastric tubes.[26]