Direct observation and measurement of Residual Gastric Volume and pH using a
Liberalized Fluid Regime
James Flowerdew MD, Andreas Taenzer MD FAAP, Douglas Howell MD, Richard Flowerdew MD
Departement of Anesthesiology and the Pancreatico-Biliary Center, Maine Medical Center, Portland, ME

Abstract
In a prospective randomized study we evaluated the impact of the traditional NPO regime versus a liberalized fluid restriction (NPO for 1 or 2 hours) on residual gastric volume (RGV) and gastric pH prior to Endoscopic Retrograde Cholangiopancreaticography (ERCP).
We found no difference in the gastric volume or pH between the study group as a whole and the control group. The group that was given liquids 1 hour prior to the procedure (NPO-1hr) had a lower RGV than the group that was given liquids 2-hours prior to the procedure (NPO-2hr) and the control group.
Most previous studies to measure RGV and Ph with liberalized fluid restriction utilized aspiration techniques via blindly passed oral or nasal gastric tubes, usually after the induction of anesthesia and intubation,1.
This study, using direct vision, demonstrates no difference in RGV in a high-risk group for delayed gastric emptying. It also raises the question of whether there is a benefit of to fluid intake about 60 minutes prior to anesthesia start.
Methods
After obtaining institutional IRB approval we enrolled 50 patients over a four months period that underwent ERCP’s. The patients were given 240 ml of blue colored liquid between 32 and 162 (mean 85) minutes prior to start of the endoscopy.
Our goal was to administer the clear liquid about 60 minutes or about 120 minutes prior to the procedure. Accurate timing of endoscopy after fluid intake was difficult in the clinical setting, so prior to data analysis we decided to split the groups into a 30-89 minute and a 90-120 minute group. Another 50 patients who followed traditional institutional NPO guidelines (NPO after midnight) served as a control group. After the induction of anesthesia in the prone position, the stomach contents were aspirated (routine part of the
procedure) through the endoscope and volume and pH as well as absence or presence of blue color were determined.
The gastroenterologist was blinded to the fluid management and was unaware if a patient was in the 1- or 2-hour or control group.
Statistical analysis was done with unpaired t-test.
Results
In the study group the average fasting time was 85 minutes [32 – 162, SD 34.84].
The average residual gastric volume (RGV) was 20.78 ml [0 – 80, SD 15.19] for the whole group; 15.89 ml [0-32, SD 9.68] for NPO-1hr; 27.0 ml [0-80, SD 18.57] for NPO-2hr. The RGV was statistically significant different for the groups (p=0.0088), with the shorter fasting group having a lower RGV.
The pH was 2.88 [0 – 7, SD 2.36] for the whole group; 3.03 [0-7, SD 2.63] for NPO-1hr; 2.67 [1-7, 1.98] for NPO-2hr. The difference in pH was not significant (p=0.596).
Blue colored liquid was present in 14 of 50 patients [28%], 8 of 28 in NPO-1hr [28.6%], 6 of 22 in NPO- 2hr [27.3%].
The average fasting time in the control group was 704 minutes [455-1200, SD 161.39]. The average RGV was 21.44 minutes [0-110, SD 20.61]. The pH was 2.52 [0-8, SD 2.24]
Discussion
We conclude that the administration of 240 ml of clear liquid less than 120 minutes prior to an ERCP does not increase RGV or alter the pH significantly. Indeed prolonged fluid restriction may increase gastric volume or lower Ph. The data suggests that fluids administered about 60-90 minutes prior to an ERCP may be more beneficial than prolonged fluid restriction. We propose that more liberal fluid guidelines may increase patient satisfaction and decrease number of case cancellations due to violation of too restrictive
guidelines.

1 Brady M, Kinn S, Stuart P. Preoperative fasting for adults to prevent perioperative complications. The Cochrane Library, Volume (4), 2004

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