The study's objective was to assess the efficacy of ultrasound in detecting solid gastric contents associated with increased aspiration risk. Upon ultrasound diagnosis of solid gastric contents in patients, sedation depth during perioperative care was adjusted to minimize reflux aspiration. Our approach involved observing stomach emptying within the endoscopic field of view, a highly precise method to validate ultrasound assessment of solid gastric contents. Findings demonstrate ultrasound's effectiveness in diagnosing or excluding solid gastric contents.
In this large sample study, a total of 5.9% [95% CI, 3.8–8.9%] of patients reported feeling full, including 7 patients with solid gastric contents and 16 patients with gastric volume exceeding 1.5 mL·kg–1, despite having met their fasting time. Of these 16 patients, 7 underwent gastroscope combined colonoscopy, while the remaining 9 patients and the 7 patients with solid contents underwent gastroscope. Despite the fact that patients undergoing gastroscope combined colonoscopy had a significantly shorter fasting period for fluids compared to those undergoing gastroscope, there was no significant difference in gastric volume between the two groups. The distribution of antrum grades 0–2, and the number of patients with gastric volume exceeding 1.5 mL·kg–1 was also similar in both groups, suggesting that extended fasting interval for fluid before gastroscope is unnecessary. Prolonged deprivation of water can lead to anxiety and insufficient circulation. Although the recommended practice guidelines for preoperative fasting advise healthy adults to consume clear beverages containing either simple or complex carbohydrates up to 2 hours before elective procedures that require general anesthesia or procedural sedation [14], its practical implementation is less than ideal. According to a clinical study conducted in China in 2018, patients typically endure dehydration for an average of 12–14 hours prior to elective surgery, in contrast to 6–9 hours in Japan and 9.36 hours in the UK [15]. This is because the fasting procedure cannot be properly followed as it is challenging to predict the precise moment an elective surgery will begin. However, this circumstance is anticipated to improve with the use of ultrasonography. Patients having gastroscope can bypass a stringent fasting period by directly evaluating their gastric volume. Furthermore, it's worth noting that solid gastric contents were exclusively observed in patients undergoing gastroscope procedures. This finding may stem from two potential factors. Firstly, patients undergoing gastroscope may have had a shorter fasting duration compared to those undergoing gastroscope combined colonoscopy procedures. Secondly, recent research suggests that combining upper endoscopy with colonoscopy may offer a protective effect against increased residual gastric contents. This protective effect is likely due to the residue-free diet routinely prescribed to patients for bowel preparation prior to colonoscopy. [8]
The 7 individuals with solid gastric contents who median fasted solids was 16 (10) h with a median age of 63 (19) years, and possible circumstances that might explain the delayed gastric emptying present in six of these patients. The endoscopy revealed duodenal bulbar stenosis in two patients, a condition that hindered the passage of stomach contents into the intestine. One of these patients had undergone gastric perforation repair and had type 2 diabetes mellitus, which could have altered the anatomical and functional aspects of the stomach. Moreover, there were two male patients in the cohort. Prior research has suggested that women are less likely to experience retained gastric food (OR 0.8 [0.8–0.9], P ≤ 0.001), and there's a correlation between gastric retention and duodenal stenosis (OR 4.1 [3.3–4.9], P ≤ 0.001) as well as type 2 diabetes (OR 1.4 [1.3–1.5], P ≤ 0.001)[9]. Another investigation focused on retained food material in individuals with a history of gastric surgery, revealing a prevalence of 19% in these patients compared to 0.3% in a control population[16]. Finally, a 71-year-old patient, who had fasted for only 9 h also presented with a similar issue. Research indicates that elderly patients may retain food in their stomachs after meals due to reduced stomach regulatory response and proximal gastric pressure [17]. No risk factors for delayed gastric solid contents emptying were identified in the last one patient. Additionally, one patient among the group was obese[18], with a gastric fluid contents exceeding 1.5 mL·kg–1. Three patients showed bile regurgitation, and seven had consumed a significant amount of clear fluids 3 to 5 h prior to endoscopy. This highlights the potential risk of increasing gastric volume associated with the consumption of a large quantity of clear liquids before gastrointestinal endoscopy. Consequently, it is important to conduct a preoperative ultrasonographic assessment of the gastric contents in these patients. The other patients with high stomach capacities did not possess any identified risk factors.
The sensitivity and specificity of ultrasound for the qualitative assessment of solid gastric contents were 85.7% and 99%, respectively. This means that during ultrasound qualitative assessment, 14.3% of patients with solid gastric contents were not detected, whereas almost all patients without solid gastric contents were correctly identified. In our study, only seven patients had solid stomach contents. Therefore, the 14.3%% discrepancy represented only one patient, whose antrum appeared empty in the semi-sitting position and filled with a small quantity of fluid in the RLD position, leading to misclassification of having solid stomach contents. This rare condition could be due to the viscosity of the solid contents, making it difficult for them to move toward the antrum in either the semi-sitting or RLD position. Fortunately, this patient did not experience reflux aspiration. Moreover, the positive and negative predictive values of ultrasound for the qualitative evaluation of solid gastric contents were 60% and 99.7%, respectively. This suggests that while the accuracy of ultrasound in predicting solid contents was relatively low, its accuracy in predicting non-solid contents was high. A positive predictive value of 60% indicates a false positive rate of 40%, which may seem high, but it is important to note that there were only four false positives in our entire study. These patients shared a common characteristic of an expanded gastric antrum and mixed echogenicity in the sinus cavity and have a median age of 72 (9) years. Our previous research found that patients > 60 year of ages showed a higher gastric antral cross-sectional area than young patients[19]. In addition, the artifacts created by air in the gastric antrum along the anterior wall of the mucosa can create the illusion of solid contents.