Gastric ultrasound performance time and difficulty: a prospective observational study.

Introduction: Point-of-care gastric ultrasound is an emerging tool in peri-operative practice. However, data on the technical challenges of gastric ultrasound, which are essential for optimised training, remain scarce. We analysed gastric ultrasound examinations performed after basic training to identify factors associated with difficulty.

Methods: This was an analysis of data from a prospective observational study evaluating the potential impact of routine pre-operative gastric ultrasound on peri-operative management in adult patients undergoing elective or emergency surgery at a single centre. Before initiation, physicians received extensive structured training with at least 30 supervised gastric sonograms before independent practice. We then used regression models to identify factors associated with deviation from a predefined sonography algorithm, performance time and scan difficulty.

Results: Seventy-three trained physicians performed 2003 ultrasound scans. Median (IQR [range]) performance time was 5 (4-6 [1-20]) min, which was achieved after 20-27 scans following structured training. Patient characteristics associated with more difficult and longer duration scans were: increase in BMI per 5 kg.m^-2 (odds ratio (95%CI) 1.57 (1.35-1.83), p < 0.001 for difficulty and percentage change coefficient (95%CI) 1.03 (1.02-1.05), p < 0.001 for duration); and male sex (odds ratio (95%CI) 3.31 (2.28-4.88), p < 0.001 for difficulty and percentage change coefficient (95%CI) 1.08 (1.04-1.12), p < 0.001, for duration). Trauma surgery (odds ratio (95%CI) 3.26 (1.88-5.68), p < 0.001), ASA physical status of 3 or 4 (odds ratio (95%CI) 1.86 (1.21-2.88), p = 0.0049) and emergency surgery (odds ratio (95%CI) 1.86 (1.20-2.89), p = 0.006) were associated with deviation from the predefined sonography algorithm.

Discussion: Approximately 50 scans are required to achieve a baseline performance of 5 min per gastric ultrasound. Future training programmes should focus on patients with obesity, male sex, higher ASA physical status and trauma.