European Journal of Cardiovascular Medicine

Aspiration of gastric contents during the perioperative period is a serious complication associated with high morbidity and mortality ^[1]. The incidence ranges from < 0.1% to 19% depending on patient and surgical factors ^[2,3]. The presence of gastric contents in the stomach is a major predisposing factor, and although the exact critical gastric volume threshold remains uncertain, healthy fasted patients generally have a gastric volume upto 1.5 ml/kg without significant aspiration risk ^[4,5].

Aspiration pneumonia, first described by Mendelson, occurs when acidic or bile gastric contents enter the lungs, causing inflammation and damage (aspiration pneumonitis) ^[6]. Perioperative aspiration can happen during induction, maintenance or postoperatively. To minimize this risk, preoperative fasting guidelines were introduced, recommending fasting for 2 hrs for clear liquids, 6 hrs for a light meal and upto 8 hrs for a fatty meal ^[7].

 In diabetic patients, delayed gastric emptying (gastroparesis) is common, affecting about 5 – 12 % and increases their risk of aspiration. This delay is due to reduced and uncoordinated gastric and duodenal contractions, along with pyloric spasms ^[8,9].

  Administration of general anesthesia further decreases lower oesophageal sphincter tone and suppresses airway reflexes, increasing aspiration risk. In diabetics, the combination of gastroparesis and anesthesia elevates this risk even more ^[10].

 There remains debate about the optimal fasting duration for diabetic patients. The European Society of Anesthesiology (ESA) guidelines 2011 suggested that diabetics could follow the same fasting protocol as healthy patients ^[11]. However, the American Society of Anesthesiologists (ASA) 2017 recommended individualized fasting durations for patients with conditions like diabetes that affect gastric emptying and fluid volume ^[7]. 

AIMS AND OBJECTIVES

AIMS:

 To compare the fasting gastric volume using ultrasonography between diabetic and non-diabetic patients posted for elective surgeries.

OBJECTIVES:

1. To evaluate the fasting gastric antral CSA, GV and GV/kg among the patients in diabetic and non-diabetic group.
2. To compare the same parameters between diabetic and non-diabetic groups after standard preoperative fasting

STUDY DESIGN AND SETTING:

 This prospective observational study was conducted in the Department of Anesthesiology at Government Cuddalore Medical College and Hospital, after obtaining approval from the Institutional Ethical and Scientific Committee. The study period extended from August 2024 to August 2025.

STUDY POPULATION:

 Patient scheduled for elective surgical procedures under anesthesia were enrolled in the study after obtaining written informed consent. A total of 100 patients were included, comprising 50 diabetic and 50 non-diabetic individuals.

INCLUSION CRITERIA:

• Age between 18 and 80 years
• Both males and females
• ASA Physical status I and II
• NPO > 8 hrs prior to elective surgery

EXCLUSION CRITERIA:

• Patient who refuses to participate
• Morbidly obese (BMI > 40 kg/m²)
• Pregnancy
• History of upper GI motility disorders
• Previous esophageal or abdominal surgeries or nasogastric tube in situ.

All the participants meeting the inclusion and exclusion criteria were enrolled after obtaining written informed consent. A comprehensive preoperative evaluation was performed, including documentation of demographic details, comorbid conditions with duration, ongoing medications, and findings from general and systemic examinations

CONDUCT OF THE STUDY

 Based on the presence or absence of diabetes mellitus, patients were categorized into diabetic and non-diabetic groups. Relevant medical history was obtained from all participants and a fasting period of 8 hrs (NPO status) was ensured prior to assessment.

Ultrasonographic evaluation was performed with the patient in a supine and RLD positions, using a Sono-Site ultrasound machine equipped with a curved array transducer (2-5 MHz, 60 mm). The observer stood on the patient’s right side, with the ultrasound machine positioned to the left for optimal probe handling and visualization.

Figure 1: Positions for gastric ultrasonography- Supine and Right Lateral Decubitus (RLD) position

Scanning was initially performed in the sagittal plane by sweeping the transducer from left to right subcostal margin to identify the gastric antrum. The patient was then positioned in the RLD position, where the gastric antrum was visualized beneath the left lobe of the liver and anterior to the pancreas, using the aorta and superior mesenteric artery as anatomical landmarks minimized intra-observer variation and standardized image acquisition.

 A still image of the gastric antrum was captured between peristaltic contractions for further measurement of the antral CSA.

Figure 2: A – Sagittal ultrasonographic model of the gastric antrum.  4.B – Sagittal sonoanatomy illustration.

Empty antrum was detected as flat antrum or “bull’s eye” target pattern as shown in (figure 3 and 4)

Figure 3                                                            Figure 4

Figure 3: Sagittal ultrasonogram picture of empty antrum depicting bulls eye target pattern (arrowheads) appearance.

Figure 4: Sagittal ultrasonogram of empty antrum displaying flat appearance.

Clear fluid was identified as distended antrum with hypoechoic content as shown in (figure - 5)

Figure 5: Antral ultrasonogram photo that shows distended antrum with clear fluid.

ASSESSMENT OF GASTRIC ANTRUM: The qualitative assessment of gastric antrum was grouped into 3 categories by Perlas as gastric antral grading system.

Table 1: Point Grading System of Gastric Antrum as Per Ultrasonographic Appearance ^[15]

The quantitative assessment of gastric antrum was calculated by measuring other gastric parameters like AP diameter, CC diameter, CSA of gastric antrum. The CSA of the gastric antrum was calculated from the still ultrasound image using the standard formula ^[14]:

                                               CSA = AP x CC x π/4

          The gastric volume (GV) was then estimated using the validated formula proposed by Perlas et al ^[15].

                                     GV (ml) = 27 + (14.6 x CSA) – (1.28 x age)

In our study, a total of 100 patients were examined. Each group of the study included 50 patients. The observation and results were obtained as follows.

Table 2: Comparison of the study groups based on gastric antral grade

Figure 6: Comparison of the study groups based on gastric antral grade

Table 3: Comparison of the study groups based on gastric antral CSA, GV and GV/kg

Figure 7: Comparison of the study groups based on gastric antral CSA

Figure 8: Comparison of the study groups based on gastric volume

Figure 9: Comparison of the study groups based on gastric volume / kg

This study compared fasting gastric volumes measured by bedside ultrasonogram in diabetic and non-diabetic patients scheduled for elective surgery. In the diabetic group, most individuals (74%) showed Grade 1, whereas 26% had Grade 0. Conversely, among non-diabetics, 54% had Grade 1 and 46% had Grade 0. This indicates that higher antral grades were more frequent among diabetics. The association between antral grade and diabetic status was statistically significant (χ² = 4.34, p = 0.037), suggesting that diabetics tend to have a higher antral grade compared to non-diabetics. The mean cross-sectional area (CSA) was also significantly greater among diabetics (5.13 ± 1.31 cm²) compared to non-diabetics (3.92 ± 1.12 cm²) (t = 4.962, p < 0.001), suggesting possible structural or physiological differences related to diabetic status. However, no statistically significant differences were observed between the two groups in terms of gastric volume (GV (ml): t = 1.501, p = 0.137) & gastric volume per kg body weight (GV/kg: t = 0.893, p = 0.374). This indicates that while CSA differ markedly between diabetics and non-diabetics, gastric volume parameters do not show significant variation.

 These findings are consistent with those of Khan et al ^[12] and Sharma et al ^[11] who evaluated gastric contents and volume of diabetic and non-diabetic patients posted for elective surgery using ultrasonogram. Our results are in partial agreement with previous studies such as those performed by Van de Putte & Perlas which demonstrated high GV in diabetic individuals but with varying levels of statistical significance. This discrepancy may be attributed to differences in study populations.

LIMITATIONS

This single-center study included only elective surgical cases with a limited sample size, which may introduce selection bias. Pregnant patients and children were excluded, and some subjectivity may have existed in the qualitative assessment of gastric contents. Future studies with larger and more diverse populations are needed to establish stronger evidence regarding gastric content aspiration risk.

Although diabetic patients showed slightly higher fasting gastric volumes after 8 hours compared to non-diabetics, the difference was not statistically significant. No patient in either group had a gastric volume exceeding the unsafe threshold^[13]   (> 1.5 ml/kg). Thus, an 8-hour preoperative fasting period appears adequate for both diabetic and non-diabetic patients.                                            

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