The American Society of Anesthesiologists advises clear fluid intake for elective patients up to 2 h before surgery. Jelly, although a solid food, is primarily composed of water, and the precise fasting time for this substance is not clearly defined [1, 2]. The aim of this study was to investigate the effect of water and jelly ingestion on cross-sectional area of the gastric antrum, when assessed by ultrasound.

Approval was gained from the local institutional review board. After written, informed consent, healthy adult participants were evaluated on two days after a fast of at least 8 h. On day 1, participants were allocated randomly using online randomisation software to either group Water (ingestion of 102 ml of bottled water) or group Jelly (ingestion of 102 ml of jelly: 78 kcal; 18 g carbohydrate; 1.6 g protein). On day 2, participants received the other intervention. An ultrasound assessment was performed before ingestion (baseline; T0) and then 120 min later (T120). All ultrasound examinations were performed in the right lateral decubitus position by the same investigator, who was blinded to group allocation. Qualitative and quantitative measurements of the gastric antrum were assessed. For quantitative assessment, anteroposterior and craniocaudal diameters were measured. The cross-sectional area of the gastric antrum was calculated using the formula for the area of an ellipse and the gastric volume was determined using the formula by Perlas et al. [3]. We also assessed the proportion of participants with gastric volume > 1.5 ml.kg^-1 and the participants' sensations of thirst and hunger at T120 (using a visual analogue scale of 0–10).

We hypothesised that jelly intake was associated with a gastric antral cross-sectional area comparable with water at T120. A non-inferiority δ of 2.8 has been described [4] but, as this can be overestimated, we assumed a non-inferiority margin of 1.5. For qualitative assessment, the stomach was classified as ‘empty’; ‘fluid’; or ‘solid’ [5]. Statistical analysis was performed using SPSS 26.0 (SPSS, Inc, Chicago, IL, USA) using t-paired test, Wilcoxon test or Fisher's exact test as appropriate. The significance level was assumed as two-tailed, with an α of 0.05, except for the non-inferiority analysis, where one-tailed p value, with an α of 0.025 was considered.

We studied 25 participants (16 female; mean (SD) age 37 (7.8) y; and mean BMI (SD) 23.6 (3.1) kg.m^-2). Fasting times were similar between groups (Table 1). At T0, there was no statistically significant differences in the antral cross-sectional area, gastric volume or the proportion of participants with gastric volume > 1.5 ml.kg^-1 (Table 1). The difference in median (95%CI) antral cross-sectional area at T120 between the groups was 0.5 (-0.4–1.4) cm^-2. The upper confidence limit of the difference in median was below the non-inferiority margin of 1.5. All other variables measured at T120 (gastric volume; proportion of participants with gastric volume > 1.5 ml.kg^-1; qualitative assessment; thirst and hunger) were similar between groups.

We found non-inferiority for the primary outcome, meaning that jelly ingestion was not linked with higher antral cross-sectional area measurements, and that jelly behaves similarly to clear fluids in terms of gastric effect. Furthermore, we found no statistically significant differences in any of the other studied outcomes.

According to previous studies, the ingestion of carbohydrate-rich drinks, up to 2 h before anaesthesia is safe [5]. However, the presence of protein content can delay gastric emptying [6], which does not seem to be the case with jelly. In the absence of solid content, a gastric volume < 1.5 ml.kg^-1 appears to be safe and common in fasting patients, mostly representing basal gastric secretions [7].

Our study has some limitations. We studied a population of healthy adults, and the results may therefore not be generalisable to all surgical patients. None of our participants experienced peri-operative anxiety that may influence gastric emptying. Therefore, the true risk of pulmonary aspiration can be difficult to estimate. It will be important to conduct a similar study in a more heterogeneous population in the peri-operative context.

美国麻醉医师协会建议择期患者在手术前 2 小时清澈摄入液体。果冻虽然是一种固体食物，但主要由水组成，这种物质的确切禁食时间尚不明确[1,2]。本研究的目的是调查通过超声评估时水和果冻摄入对胃窦横截面积的影响。

获得了当地机构审查委员会的批准。在书面知情同意后，健康成年参与者在禁食至少 8 小时后两天进行评估。第 1 天，参与者使用在线随机化软件被随机分配到水组（摄入 102 毫升瓶装水）或果冻组（摄入 102 毫升果冻：78 大卡;18 克碳水化合物;1.6 克蛋白质）。第 2 天，参与者接受了另一种干预。摄入前进行超声评估（基线;T0），然后 120 分钟后 （T120）。所有超声检查均由同一研究者在右侧卧位进行，该研究者对组分配不知情。评估胃窦的定性和定量测量。为了进行定量评估，测量了前后径和颅尾直径。胃窦的横截面积使用椭圆面积公式计算，胃体积使用 Perlas 等人的公式确定 [3]。我们还评估了胃体积 > 1.5 ^ml.kg-1 的参与者比例以及 T120 时参与者的口渴和饥饿感（使用 0-10 的视觉模拟量表）。

我们假设果冻摄入量与胃窦横截面积相关，与 T120 的水相当。已经描述了 2.8 的非劣效性δ [4]，但由于这可能被高估，我们假设非劣效性边际为 1.5。对于定性评估，胃被归类为“空的”;'fluid' ;或 'solid' [5]。使用 SPSS 26.0 （SPSS， Inc， Chicago， IL， USA） 酌情使用 t 配对检验、Wilcoxon 检验或 Fisher 精确检验进行统计分析。显着性水平假设为双尾，α为 0.05，但非劣效性分析除外，其中考虑了单尾 p 值，α为 0.025。

我们研究了 25 名参与者 （16 名女性;平均 （SD） 年龄 37 （7.8） 岁;平均 BMI （SD） 23.6 （3.1） ^kg.m-2）。各组之间的禁食时间相似（表 1）。在 T0 时，胃窦横截面积、胃体积或胃体积 > 1.5 ^ml.kg-1 的参与者比例没有统计学意义差异（表 1）。两组之间 T120 的中位 （95%CI） 胃窦横截面积差异为 0.5 （-0.4–1.4） ^cm-2。中位数差异的置信上限低于 1.5 的非劣效性边缘。在 T120 测量的所有其他变量（胃容量;胃容量 > 1.5 ^ml.kg-1 的参与者比例;定性评估;口渴和饥饿）在组间相似。

我们发现主要结局的非劣效性，这意味着果冻摄入与较高的胃窦横截面积测量值无关，并且果冻在胃作用方面的行为与透明液体相似。此外，我们发现任何其他研究结局均无统计学意义差异。

根据以前的研究，在麻醉前 2 小时摄入富含碳水化合物的饮料是安全的 [5]。然而，蛋白质含量的存在会延迟胃排空 [6]，而果冻似乎并非如此。在没有固体含量的情况下，胃体积 < 1.5 ^ml.kg-1 似乎是安全且常见的空腹患者，主要代表基底胃分泌物 [7]。

我们的研究有一些局限性。我们研究了一群健康的成年人，因此结果可能无法推广到所有手术患者。我们的参与者都没有经历可能影响胃排空的围手术期焦虑。因此，肺误吸的真实风险可能难以估计。在围手术期背景下，在异质性更强的人群中进行类似的研究将很重要。