Decompression of the GI Tract

Administration of Oral Agents

Gastrointestinal Hemorrhage

Pancreatitis

Trauma

DECOMPRESSION OF THE GI TRACT

Gastric decompression is required in patients unable to pass stomach fluids through the distal gut for mechanical reasons (e.g. bowel obstruction or gastric outlet obstruction.) Patients with severe vomiting refractory to medical management may also benefit from a NGT. In the critically-ill intubated patient (medical or trauma), NGT or orogastric tube (OGT) placement is required to decompress the stomach to prevent aspiration of stomach contents.

ADMINISTRATION OF ORAL AGENTS

Toxic ingestions | Medications and contrast | Hypothermia

Toxic Ingestions

Charcoal may be given to overdose patients through a NGT if the patient refuses to drink the solution. In the somnolent overdose patient endotracheal intubation should be considered prior to infusion of charcoal via a NGT as the airway reflexes may be diminished, resulting in high risk of aspiration. Gastric lavage (i.e. the "stomach pump") has fallen out of favor in most overdose situations; current recommendations reserve this procedure for patients who have taken a massive overdose of a particularly toxic substance (e.g. tricyclic antidepressants) who present within 30-60 minutes of the ingestion. 2 When gastric lavage is undertaken, the tube used (most commonly, the Ewald tube) is of larger caliber than the standard NGT, to facilitate removal of pill fragments. The insertion of an Ewald tube should be considered a separate procedure than NGT insertion and is not discussed in this workshop.

Medications and Radiological Contrast Agents

NGTs may be required to administer medications or contrast media (e.g. Gastrograffin) in trauma or medical patients unable to take them orally.

Hypothermia

Gastric lavage with warm fluid infused through a NGT may be used as an active core rewarming technique in cases of severe hypothermia (<32.2 ° C). Care must be taken to avoid excessive fluid administration and electrolyte fluxes. 3

Classic medical teaching calls for the insertion of a NGT in cases of gastrointestinal hemorrhage, both as a diagnostic and therapeutic tool. 4 Diagnostically, a NGT is inserted to "localize" the source of the bleeding and to ascertain if there is continued "active" bleeding. In theory, if blood / coffee grounds are aspirated from the NGT, then bleeding proximal to ligament of Trietz is present; and if absent, upper GI bleeding is excluded-- provided that bile is present in the aspirate. (The presence of bile is required to assure that duodenal contents were sampled.) However, the true value of NGT lavage in GI bleeding has been called into question in the literature. 4 , 5 , 6 , 7 , 8 Problems include:

• Poor sensitivity, estimated at 79%. 7 False negatives can occur in cases of duodenal bleeding associated with pylorus spasm or edema. (N.B. In the presence of grossly bloody fluid or large amounts of "coffee grounds", the sensitivity is estimated to be 98%) 5 . Additionally, occlusion of the distal end of the NGT by clots or gastric mucosa may prevent the aspiration of fresh blood even in the presence of ongoing bleeding. 4
• Poor specificity, estimated at 53-55%. 6 , 7 False positives can occur with swallowed nasal or oropharyngeal blood.
• Inaccuracy of the determination of the presence of bile in the aspirate. Cuellar et.al. found no association between GI fellows' clinical assessment of bile in the aspirate and laboratory confirmation of the presence of bile acids in the same samples. 7

Gastric lavage with iced saline or tap water was once recommended as therapeutic maneuver for upper gastrointestinal hemorrhage, but this technique has fallen out of favor. 5 , 9 No data exists that suggest iced lavage decreases bleeding; in fact, it may exacerbate blood loss via inhibition of coagulation factors and platelets.

Despite these drawbacks, there may be utility of a NGT in selected patients with GI bleeding. NGT aspirates may provide prognostic data: the presence of bright red blood in the aspirate is associated with an 18% mortality rate vs. 6% in those whose aspirate is clear. 6 Furthermore, evacuation of blood and clots in the stomach may facilitate the endoscopist's visualization of the gastric and duodenal mucosa. 9

PANCREATITIS

Another classical teaching is the use of a NGT in acute pancreatitis. It has been hypothesized that NGT suction reduces the amount of acidic gastric juice reaching the duodenum, resulting in decreased pancreatic secretions and thus an improved clinical course. However, numerous studies have demonstrated that in mild to moderate pancreatitis, NGTs offer no reduction in the duration of abdominal pain, ileus, complications (such as pseuodocysts, abscesses, and biliary obstruction), or in the amounts of intravenous fluid and narcotics required. 10 , 11 , 12 , 13 , 14 , 15 In fact, several studies revealed that NGTs resulted in longer hospitalizations, protracted nausea and vomiting, prolonged hyperamylasemia, and delays in the resumption of oral intake. 10 , 13 , 15

None of the aforementioned studies included patients with severe pancreatitis associated with significant ileus. Patients with this presentation may benefit from intemittent gastric suctioning and NGT insertion should be carefully considered.