ANALYSIS, GASTRIC ACID STIMULATION TEST, AND pH MONITORING
of the gastric juice yields information about the secretory activity of the
gastric mucosa and the presence or degree of gastric retention in patients
thought to have pyloric or duodenal obstruction. It is also useful for
diagnosing diseases such as Zollinger-Ellison syndrome.
patient is kept NPO for 8 to 12 hours before the proce-dure. Any medications
that affect gastric secretions are withheld for 24 to 48 hours before the test.
Smoking is not allowed on the morning before the test, because it increases
gastric secretions. A small nasogastric tube with a catheter tip marked at
various points is inserted through the nose. When the tube is at a point
slightly less than 50 cm (21 inches) distant, it should be within the stom-ach,
lying along the greater curvature. Once in place, the tube is secured to the
patient’s cheek and the patient is placed in a semi-reclining position. The
entire stomach contents are aspirated by gentle suction into a syringe, and
gastric samples are collected every 15 minutes for the next hour.
gastric acid stimulation test usually is performed in con-junction with gastric
analysis. Histamine or pentagastrin is ad-ministered subcutaneously to
stimulate gastric secretions. It is important to inform the patient that this
injection may produce a flushed feeling. The nurse monitors blood pressure and
pulse frequently to detect hypotension. Gastric specimens are collected after
the injection every 15 minutes for 1 hour and are labeled to indicate the time
of specimen collection after histamine injection. The volume and pH of the
specimen are measured. In certain in-stances, cytologic study by the
Papanicolaou technique may be used to determine the presence or absence of malignant
cells. Enzyme analysis of the gastric juice may be indicated.
diagnostic information to be gained from gastric analysis includes the ability
of the mucosa to secrete HCl. This ability is altered in various disease
Pernicious anemia—patients with this disease
secrete no acid under basal conditions or after stimulation
Severe chronic atrophic gastritis or gastric
cancer—patients with these diseases secrete little or no acid
Peptic ulcer—patients with peptic ulcers secrete some
Duodenal ulcers—patients with duodenal ulcers
usually secrete an excess amount of acid
reflux of gastric acid may be diagnosed by ambu-latory pH monitoring. The
patient is NPO for 6 hours before the test, and all medications affecting
gastric secretions are withheld for 24 to 36 hours before the test. A probe
that measures pH is placed through the nose and into position about 5 inches
above the lower esophageal sphincter. It is connected to an external recording
device and is worn for 24 hours while the patient con-tinues his or her normal
daily activities. The end result is a com-puter analysis and graphic display of
the results. This test allows for the direct correlation between chest pain and
reflux episodes (Wolfe, 2000).
Bernstein test may be performed to evaluate complaints of acid-related chest or
epigastric pain. HCl is instilled through a small feeding tube positioned in
the esophagus. This is done to try to elicit reported chest pain. Resultant
signs and symptoms are compared with the usual symptoms the patient reports.
How-ever, since the advent of ambulatory pH monitoring, this previ-ously
popular evaluation tool is used infrequently (Wolfe, 2000).