QUANTITATIVE-EVALUATION OF GASTRIC CONTENTS USING ULTRASOUND

Study Objectives: To describe a method of the authors' design for esti mating gastric volume quantitatively using ultrasound and to evaluate the usefulness of this method in the clinical settng. Design: Prospect ive, two,phase clinical study. Setting: University hospital. Patients and volunteers: Phase 1 study: 31 patients who were undergoing general anesthesia and had no gastrointestinal disorder. Phase 2 study: 8 hea lthy volunteers. Interventions: With each subject in the sitting posit ion, a cross-sectional view of the stomach teas obtained via ultrasoun d along the median line of the epigastric region. The cross-sectional area of the stomach (CSA) was measured by the analysis unit on the bas is of the trace-enclosure method, and a mean value was obtained from t riplicate measurements. Measurements and Main Results: In the phase 1 study, CSA was measured after the patient had fasted for 1 hour, 4 hou rs, and more than 8 hours. CSA (cm(2)) was 19.2 +/- 0.9 cm(2) at 1 hou r, 11.0 +/- 0.7 cm(2) at 4 hours, and 5.5 +/- 0.4 cm(2) at more than g hours. That is, CSA significantly decreased as fasting time was prolo nged (p < 0.001 for 1 hour vs. more than 8 hours and 4 hours vs. more than 8 hours). Mast of the patients (87%) who fasted for more than 8 h ours had a CSA less than 8.0 cm(2). In the phase 2 study, after patien ts had fasted for more than 8 hours, CSA was measured both before and 5 minutes after the patient drank 50 ml of milk. CSA was 5.0 +/- 0.5 c m(2) before and 8.5 +/- 0.9 cm(2) after ingestion of the milk (p < 0.0 01). All subjects had a CSA less than. 8.0 cm(2) before drinking the m ilk, whereas only 2 of 8 patients had a CSA less than 8.0 cm(2) after. Conclusions: This method would be useful to estimate gastric contents quantitatively, and a CSA of 8.0 cm(2) might be a valid indicator of an empty stomach.