Introduction

Pulmonary aspiration of gastric contents has been reported to be one of the main causes of mortality related to general anesthesia⁽¹⁾. Several factors may contribute to the pathophysiology of this complication, especially significant amount of gastric contents due to absence of adequate preoperative fasting in the case of emergency surgery.

Ultrasonographic examination of the antral area is a noninvasive tool allowing preoperative assessment of gastric contents and volume^(2–4). Its use in clinical practice would be of interest to help the anesthesiologist to assess the risk of pulmonary aspiration of gastric contents, particularly in emergency patients, for whom the gastric status may remain uncertain⁽⁵⁾. However, its use in elective patients for the diagnosis of unexpected full stomach has never been reported.

In this article, we report two cases of patients presenting for elective surgery with a significantly full stomach diagnosed through performing by chance an ultrasound examination of their antral area. The patients provided their written informed consent for the publication of this article.

Cases

The first patient was a 51-yr-old man, American Society of Anesthesiologists (ASA) physical status I, height: 171 cm, weight: 73 kg, scheduled for a day-case carpal tunnel syndrome surgery under regional anesthesia. This patient had been seen in preoperative anesthetic consultation, where, notably, all appropriate information regarding preoperative fasting was given. Ten days after this consultation, this patient presented at our day-case surgery unit. On his arrival, he was requested to complete a pre-anesthetic questionnaire to ensure that preoperative fasting was adequately followed. Before performing the axillary brachial plexus blockade, ultrasonographic assessment of gastric contents was performed by a physician who wished to train for this technique. The examining physician was surprised by finding homogenous echogenic contents in the antrum, whose volume was calculated as 1279 mm² (Fig. 1). This diagnosis was later confirmed by an experienced sonographer. The patient finally admitted that he had eaten some cakes in the morning, prior to his arrival at the hospital, 4 hours before the ultrasound examination. This patient was consequently not operated.

Fig. 1

Ultrasound image of the antrum of the first patient. The antrum is dilated with homogenous echogenic content, corresponding to solid contents

The second patient was a 62-yr-old woman, ASA physical status II, height: 161 cm, weight: 51 kg, scheduled for an elective oph-thalmologic surgery. This patient did not meet all the required criteria for day-case surgery, and was consequently hospitalized the day before the surgery. She was usually treated by ramipril administered in the evening for chronic hypertension, and did not report any other medical history at the preoperative anesthetic consultation. After her arrival in the operating room, an ultrasound examination of the stomach was performed, within the context of practical teaching of the technique. This examination showed significant gastric content, with fluids and solid particles visualized in a largely dilated antrum (Fig. 2, antral area measured in semi-recumbent position: 1391 mm²). The patient confirmed that she had not eaten anything since her last meal (soup, bread, yoghurt) taken more than 14 hours before her arrival in the operating room. In fact, as she was hospitalized, she could not access any food during the night preceding the intervention. She never suffered from gastro-esophageal reflux, nor presented any gastrointestinal disease. This patient was finally operated under topical anesthesia.

Fig. 2

Ultrasound image of the antrum of the second patient. The antrum is dilated, with both echogenic and non-echogenic contents, corresponding to liquid and solid contents

Discussion

We report two cases of fortuitous diagnosis of full stomach made by performing ultrasound assessment of gastric contents in elective patients.

Ultrasound measurement of antral area is a safe and noninvasive bedside examination of the gastric volume^{(2, 4, 5)}. As the antrum is located far from the gastric air bubble and the costal margin, its visualization is achieved for a large proportion of non-obese and obese patients^{(2, 4)}. In practice, examination of the antrum should be performed on patients placed either in a semi-recumbent position, or in a right lateral decubitus position^(2–4). Using a convex 2–5.5 MHz transducer, the sagittal plane passing through the left lobe of the liver and the abdominal aorta allows qualitative analysis of the gastric antrum and standardized measurements of antral area, with high intra- and inter-rater reliability⁽⁶⁾. Antral area is calculated using the following formula: antral area = (ϖ × longitudinal diameter × anteroposterior diameter) / 4, where both diameters of the section of the antrum are measured from serosa to serosa. Antral area <340 mm² allows the conclusion that there is no significant gastric content⁽²⁾. Conversely, antral area >340 mm², and visualization of a distended antrum, with echoic (solid) and/or anechoic (fluid) content⁽³⁾, as reported in the two cases described in this article, corresponds to significant, and potentially dangerous, gastric contents⁽⁷⁾.

The first case shows that some elective patients do not follow preoperative fasting instructions. Not respecting preoperative fasting might probably be more frequent in outpatients than in inpatients because of easier access to food combined with the habit of breakfast in the morning, although this hypothesis has never been assessed. The second case illustrates that prolonged preoperative fasting does not guarantee that the stomach of elective patients is completely empty on induction of anesthesia. In the absence of a gastrointestinal disease, no other explanation than anxiety or an e xtreme example of inter-individual variability for gastric emptying could be given as concerns the cause of the delayed gastric emptying.

Unestablished significant gastric content may explain some of the cases of pulmonary aspiration occurring in patients without any other apparent risk factors for this complication⁽⁸⁾. Thus, these two cases raise the interest of performing systematic ultrasonographic assessment of gastric contents in elective patients to detect those with a full stomach during the preoperative period. However, although based on a simple tool, such a procedure would be time consuming, as it would require sufficient numbers of ultrasound devices in operating rooms. The cost/benefits ratio of such strategy should be first assessed, prior to recommending routine ultrasound preoperative assessment of gastric contents in elective patients⁽⁹⁾.

In conclusion, these two cases illustrate that some elective surgical patients may have significant gastric contents that may expose them to an increased risk for pulmonary aspiration of gastric contents in the case of general anesthesia. Full stomach may be easily detected by performing preoperative ultrasound examination of the gastric antrum. Further studies are, therefore, required to assess whether such ultrasound examination should be routinely performed prior to general anesthesia in elective patients.