Gastric aspirate is a medical procedure that withdraws fluid from the stomach through a tube. This diagnostic technique allows clinicians to evaluate health conditions by analyzing the stomach’s contents. The process provides a direct sample from the upper digestive system for testing.
Reasons for Gastric Aspiration
A primary reason for gastric aspiration is to confirm the correct placement of a nasogastric (NG) tube used for feeding or medication. The tube must be in the stomach and not the lungs, which could lead to serious complications. Aspirating stomach contents verifies the tube’s location before use.
The procedure is also used to diagnose infections like pulmonary tuberculosis in infants and young children who cannot produce sputum for testing. During sleep, respiratory secretions containing bacteria are swallowed and collect in the stomach. Collecting these secretions allows clinicians to test for Mycobacterium tuberculosis.
Gastric aspiration can also assess for bleeding in the upper gastrointestinal tract or relieve pressure in the stomach. If a blockage causes fluid or gas to build up, the stomach can become distended. Removing the excess contents, known as decompression, alleviates symptoms and helps identify an obstruction or internal bleeding.
The Gastric Aspiration Procedure
The process of gastric aspiration involves a nasogastric tube, a thin, flexible tube passed through the nose and into the stomach. If a patient already has an NG tube for feeding, it can be used for the aspiration. The patient is asked to fast for several hours beforehand.
Once the tube is in the correct position, a syringe is attached to the external end. A clinician then gently pulls back on the plunger, creating negative pressure that draws fluid from the stomach into the syringe.
The experience can cause temporary discomfort, such as a gagging sensation when the tube is inserted. The aspiration itself is quick and performed by a trained nurse or doctor. In some cases, saline is pushed through the tube and into the stomach to help increase the volume of fluid collected for analysis.
Analysis of Gastric Fluid
After the gastric fluid is collected, the first step is a visual inspection. The color and consistency of the aspirate offer clues about the patient’s condition. Clear, tan, or grassy-green fluid is considered normal, while a dark, granular “coffee ground” appearance suggests old blood from previous bleeding.
A key part of the analysis is testing the fluid’s pH level. Stomach contents are highly acidic, and a pH test done at the bedside can confirm the sample is from the stomach. A low pH reading, between 1 and 5, helps verify the tube’s correct placement.
The collected sample may also be sent to a laboratory for detailed examination. Technicians can perform cultures to identify bacteria or viruses causing an infection. For suspected tuberculosis, the sample is tested for Mycobacterium tuberculosis using techniques like Acid-Fast Bacillus (AFB) staining or molecular tests.